def main():
# Get the path for the mesh to load from the program argument
if(len(sys.argv) == 3):
partString = sys.argv[1]
if partString not in ['part1','part2','part3']:
print("ERROR part specifier not recognized. Should be one of 'part1', 'part2', or 'part3'")
exit()
filename = sys.argv[2]
else:
print("ERROR: Incorrect call syntax. Proper syntax is 'python Assignment3.py partN path/to/your/mesh.obj'.")
exit()
# Read in the mesh
mesh = HalfEdgeMesh(readMesh(filename))
# Create a viewer object
winName = 'DDG Assignment3 ' + partString + '-- ' + os.path.basename(filename)
meshDisplay = MeshDisplay(windowTitle=winName)
meshDisplay.setMesh(mesh)
###################### BEGIN YOUR CODE
# implement the body of each of these functions
############################
# Part 0: Helper functions #
############################
# Implement a few useful functions that you will want in the remainder of
# the assignment.
@property
@cacheGeometry
def cotanWeight(self):
"""
Return the cotangent weight for an edge. Since this gets called on
an edge, 'self' will be a reference to an edge.
This will be useful in the problems below.
Don't forget, everything you implemented for the last homework is now
available as part of the library (normals, areas, etc). (Moving forward,
Vertex.normal will mean area-weighted normals, unless otherwise specified)
"""
return 0.0 # placeholder value
@property
@cacheGeometry
def dualArea(self):
"""
Return the dual area associated with a vertex. Since this gets called on
a vertex, 'self' will be a reference to a vertex.
Recall that the dual area can be defined as 1/3 the area of the surrounding
faces.
"""
return 0.0 # placeholder value
def enumerateVertices(mesh):
"""
Assign a unique index from 0 to (N-1) to each vertex in the mesh. Should
return a dictionary containing mappings {vertex ==> index}.
You will want to use this function in your solutions below.
"""
return None # placeholder value
#################################
# Part 1: Dense Poisson Problem #
#################################
# Solve a Poisson problem on the mesh. The primary function here
# is solvePoissonProblem_dense(), it will get called when you run
# python Assignment3.py part1 /path/to/your/mesh.obj
# and specify density values with the mouse (the press space to solve).
#
# Note that this code will be VERY slow on large meshes, because it uses
# dense matrices.
def buildLaplaceMatrix_dense(mesh, index):
"""
Build a Laplace operator for the mesh, with a dense representation
'index' is a dictionary mapping {vertex ==> index}
Returns the resulting matrix.
"""
return None # placeholder value
def buildMassMatrix_dense(mesh, index):
"""
Build a mass matrix for the mesh.
Returns the resulting matrix.
"""
return None # placeholder value
def solvePoissonProblem_dense(mesh, densityValues):
"""
Solve a Poisson problem on the mesh. The results should be stored on the
vertices in a variable named 'solutionVal'. You will want to make use
of your buildLaplaceMatrix_dense() function from above.
densityValues is a dictionary mapping {vertex ==> value} that specifies
densities. The density is implicitly zero at every vertex not in this
dictionary.
When you run this program with 'python Assignment3.py part1 path/to/your/mesh.obj',
you will get to click on vertices to specify density conditions. See the
assignment document for more details.
"""
pass # remove this line once you have implemented the method
##################################
# Part 2: Sparse Poisson Problem #
##################################
# Solve a Poisson problem on the mesh. The primary function here
# is solvePoissonProblem_sparse(), it will get called when you run
# python Assignment3.py part2 /path/to/your/mesh.obj
# and specify density values with the mouse (the press space to solve).
#
# This will be very similar to the previous part. Be sure to see the wiki
# for notes about the nuances of sparse matrix computation. Now, your code
# should scale well to larger meshes!
def buildLaplaceMatrix_sparse(mesh, index):
"""
Build a laplace operator for the mesh, with a sparse representation.
This will be nearly identical to the dense method.
'index' is a dictionary mapping {vertex ==> index}
Returns the resulting sparse matrix.
"""
return None # placeholder value
def buildMassMatrix_sparse(mesh, index):
"""
Build a sparse mass matrix for the system.
Returns the resulting sparse matrix.
"""
return None # placeholder value
def solvePoissonProblem_sparse(mesh, densityValues):
"""
Solve a Poisson problem on the mesh, using sparse matrix operations.
This will be nearly identical to the dense method.
The results should be stored on the vertices in a variable named 'solutionVal'.
densityValues is a dictionary mapping {vertex ==> value} that specifies any
densities. The density is implicitly zero at every vertex not in this dictionary.
Note: Be sure to look at the notes on the github wiki about sparse matrix
computation in Python.
When you run this program with 'python Assignment3.py part2 path/to/your/mesh.obj',
you will get to click on vertices to specify density conditions. See the
assignment document for more details.
"""
pass # remove this line once you have implemented the method
###############################
# Part 3: Mean Curvature Flow #
###############################
# Perform mean curvature flow on the mesh. The primary function here
# is meanCurvatureFlow(), which will get called when you run
# python Assignment3.py part3 /path/to/your/mesh.obj
# You can adjust the step size with the 'z' and 'x' keys, and press space
# to perform one step of flow.
#
# Of course, you will want to use sparse matrices here, so your code
# scales well to larger meshes.
def buildMeanCurvatureFlowOperator(mesh, index, h):
"""
Construct the (sparse) mean curvature operator matrix for the mesh.
It might be helpful to use your buildLaplaceMatrix_sparse() and
buildMassMatrix_sparse() methods from before.
Returns the resulting matrix.
"""
return None # placeholder value
def meanCurvatureFlow(mesh, h):
"""
Perform mean curvature flow on the mesh. The result of this operation
is updated positions for the vertices; you should conclude by modifying
the position variables for the mesh vertices.
h is the step size for the backwards euler integration.
When you run this program with 'python Assignment3.py part3 path/to/your/mesh.obj',
you can press the space bar to perform this operation and z/x to change
the step size.
Recall that before you modify the positions of the mesh, you will need
to set mesh.staticGeometry = False, which disables caching optimizations
but allows you to modfiy the geometry. After you are done modfiying
positions, you should set mesh.staticGeometry = True to re-enable these
optimizations. You should probably have mesh.staticGeometry = True while
you assemble your operator, or it will be very slow.
"""
pass # remove this line once you have implemented the method
###################### END YOUR CODE
Edge.cotanWeight = cotanWeight
Vertex.dualArea = dualArea
# A pick function for choosing density conditions
densityValues = dict()
def pickVertBoundary(vert):
value = 1.0 if pickVertBoundary.isHigh else -1.0
print(" Selected vertex at position:" + printVec3(vert.position))
print(" as a density with value = " + str(value))
densityValues[vert] = value
pickVertBoundary.isHigh = not pickVertBoundary.isHigh
pickVertBoundary.isHigh = True
# Run in part1 mode
if partString == 'part1':
print("\n\n === Executing assignment 2 part 1")
print("""
Please click on vertices of the mesh to specify density conditions.
Alternating clicks will specify high-value (= 1.0) and low-value (= -1.0)
density conditions. You may select as many density vertices as you want,
but >= 2 are necessary to yield an interesting solution. When you are done,
press the space bar to execute your solver and view the results.
""")
meshDisplay.pickVertexCallback = pickVertBoundary
meshDisplay.drawVertices = True
def executePart1Callback():
print("\n=== Solving Poisson problem with your dense solver\n")
# Print and check the density values
print("Density values:")
for key in densityValues:
print(" " + str(key) + " = " + str(densityValues[key]))
if len(densityValues) < 2:
print("Aborting solve, not enough density vertices specified")
return
# Call the solver
print("\nSolving problem...")
t0 = time.time()
solvePoissonProblem_dense(mesh, densityValues)
tSolve = time.time() - t0
print("...solution completed.")
print("Solution took {:.5f} seconds.".format(tSolve))
print("Visualizing results...")
# Error out intelligently if nothing is stored on vert.solutionVal
for vert in mesh.verts:
if not hasattr(vert, 'solutionVal'):
print("ERROR: At least one vertex does not have the attribute solutionVal defined.")
exit()
if not isinstance(vert.solutionVal, float):
print("ERROR: The data stored at vertex.solutionVal is not of type float.")
print(" The data has type=" + str(type(vert.solutionVal)))
print(" The data looks like vert.solutionVal="+str(vert.solutionVal))
exit()
# Visualize the result
# meshDisplay.setShapeColorFromScalar("solutionVal", definedOn='vertex', cmapName="seismic", vMinMax=[-1.0,1.0])
meshDisplay.setShapeColorFromScalar("solutionVal", definedOn='vertex', cmapName="seismic")
meshDisplay.generateAllMeshValues()
meshDisplay.registerKeyCallback(' ', executePart1Callback, docstring="Solve the Poisson problem and view the results")
# Start the GUI
meshDisplay.startMainLoop()
# Run in part2 mode
elif partString == 'part2':
print("\n\n === Executing assignment 2 part 2")
print("""
Please click on vertices of the mesh to specify density conditions.
Alternating clicks will specify high-value (= 1.0) and low-value (= -1.0)
density conditions. You may select as many density vertices as you want,
but >= 2 are necessary to yield an interesting solution. When you are done,
press the space bar to execute your solver and view the results.
""")
meshDisplay.pickVertexCallback = pickVertBoundary
meshDisplay.drawVertices = True
def executePart2Callback():
print("\n=== Solving Poisson problem with your sparse solver\n")
# Print and check the density values
print("Density values:")
for key in densityValues:
print(" " + str(key) + " = " + str(densityValues[key]))
if len(densityValues) < 2:
print("Aborting solve, not enough density vertices specified")
return
# Call the solver
print("\nSolving problem...")
t0 = time.time()
solvePoissonProblem_sparse(mesh, densityValues)
tSolve = time.time() - t0
print("...solution completed.")
print("Solution took {:.5f} seconds.".format(tSolve))
print("Visualizing results...")
# Error out intelligently if nothing is stored on vert.solutionVal
for vert in mesh.verts:
if not hasattr(vert, 'solutionVal'):
print("ERROR: At least one vertex does not have the attribute solutionVal defined.")
exit()
if not isinstance(vert.solutionVal, float):
print("ERROR: The data stored at vertex.solutionVal is not of type float.")
print(" The data has type=" + str(type(vert.solutionVal)))
print(" The data looks like vert.solutionVal="+str(vert.solutionVal))
exit()
# Visualize the result
# meshDisplay.setShapeColorFromScalar("solutionVal", definedOn='vertex', cmapName="seismic", vMinMax=[-1.0,1.0])
meshDisplay.setShapeColorFromScalar("solutionVal", definedOn='vertex', cmapName="seismic")
meshDisplay.generateAllMeshValues()
meshDisplay.registerKeyCallback(' ', executePart2Callback, docstring="Solve the Poisson problem and view the results")
# Start the GUI
meshDisplay.startMainLoop()
# Run in part3 mode
elif partString == 'part3':
print("\n\n === Executing assignment 2 part 3")
print("""
Press the space bar to perform one step of mean curvature
flow smoothing, using your solver. Pressing the 'z' and 'x'
keys will decrease and increase the step size (h), respectively.
""")
stepSize = [0.01]
def increaseStepsize():
stepSize[0] += 0.001
print("Increasing step size. New size h="+str(stepSize[0]))
def decreaseStepsize():
stepSize[0] -= 0.001
print("Decreasing step size. New size h="+str(stepSize[0]))
meshDisplay.registerKeyCallback('z', decreaseStepsize, docstring="Increase the value of the step size (h) by 0.1")
meshDisplay.registerKeyCallback('x', increaseStepsize, docstring="Decrease the value of the step size (h) by 0.1")
def smoothingStep():
print("\n=== Performing mean curvature smoothing step\n")
print(" Step size h="+str(stepSize[0]))
# Call the solver
print(" Solving problem...")
t0 = time.time()
meanCurvatureFlow(mesh, stepSize[0])
tSolve = time.time() - t0
print(" ...solution completed.")
print(" Solution took {:.5f} seconds.".format(tSolve))
print("Updating display...")
meshDisplay.generateAllMeshValues()
meshDisplay.registerKeyCallback(' ', smoothingStep, docstring="Perform one step of your mean curvature flow on the mesh")
# Start the GUI
meshDisplay.startMainLoop()
def main(inputfile, show=False, StaticGeometry=False):
# Get the path for the mesh to load, either from the program argument if
# one was given, or a dialog otherwise
if (len(sys.argv) > 1):
filename = sys.argv[1]
elif inputfile is not None:
filename = inputfile
else:
string1 = "ERROR: No file name specified. "
string2 = "Proper syntax is 'python Assignment2.py path/to/your/mesh.obj'."
print(string1 + string2)
exit()
# Read in the mesh
mesh = HalfEdgeMesh(readMesh(filename), staticGeometry=StaticGeometry)
# Create a viewer object
winName = 'DDG Assignment2 -- ' + os.path.basename(filename)
if show:
meshDisplay = MeshDisplay(windowTitle=winName)
meshDisplay.setMesh(mesh)
###################### BEGIN YOUR CODE
# implement the body of each of these functions
#
#
# def buildLaplaceMatrix_dense(mesh, index):
# """
# Build a Laplace operator for the mesh, with a dense representation
#
# 'index' is a dictionary mapping {vertex ==> index}
#
# Returns the resulting matrix.
# """
# #index_map = mesh.enumerateVertices()
# index_map = enumerateVertices(mesh)
#
# return Laplacian
@property
@cacheGeometry
def faceArea(self):
"""
Compute the area of a face.
Though not directly requested, this will be
useful when computing face-area weighted normals below.
This method gets called on a face,
so 'self' is a reference to the
face at which we will compute the area.
"""
v = list(self.adjacentVerts())
a = 0.5 * norm(
cross(v[1].position - v[0].position,
v[2].position - v[0].position))
return a
@property
@cacheGeometry
def faceNormal(self):
"""
Compute normal at a face of the mesh.
Unlike at vertices, there is one very
obvious way to do this, since a face
uniquely defines a plane.
This method gets called on a face,
so 'self' is a reference to the
face at which we will compute the normal.
"""
v = list(self.adjacentVerts())
n = normalize(
cross(v[1].position - v[0].position,
v[2].position - v[0].position))
return n
@property
@cacheGeometry
def vertexNormal_EquallyWeighted(self):
"""
Compute a vertex normal using the 'equally weighted' method.
This method gets called on a vertex,
so 'self' is a reference to the
vertex at which we will compute the normal.
http://brickisland.net/cs177/?p=217
Perhaps the simplest way to get vertex normals
is to just add up the neighboring face normals:
"""
normalSum = np.array([0.0, 0.0, 0.0])
for face in self.adjacentFaces():
normalSum += face.normal
n = normalize(normalSum)
#issue:
# two different tessellations of the same geometry
# can produce very different vertex normals
return n
@property
@cacheGeometry
def vertexNormal_AreaWeighted(self):
"""
Compute a vertex normal using
the 'face area weights' method.
This method gets called on a vertex,
so 'self' is a reference to the
vertex at which we will compute the normal.
The area-weighted normal vector for this vertex"""
normalSum = np.array([0.0, 0.0, 0.0])
for face in self.adjacentFaces():
normalSum += face.normal * face.area
n = normalize(normalSum)
#print 'computed vertexNormal_AreaWeighted n = ',n
return n
@property
@cacheGeometry
def vertexNormal_AngleWeighted(self):
"""
element type : vertex
Compute a vertex normal using the
'Tip-Angle Weights' method.
This method gets called on a vertex,
so 'self' is a reference to the
vertex at which we will compute the normal.
A simple way to reduce dependence
on the tessellation is to weigh face normals
by their corresponding tip angles theta, i.e.,
the interior angles incident on the vertex of interest:
"""
normalSum = np.array([0.0, 0.0, 0.0])
for face in self.adjacentFaces():
vl = list(face.adjacentVerts())
vl.remove(self)
v1 = vl[0].position - self.position
v2 = vl[1].position - self.position
# norm ->no need for check:
# it doesn not matter what the sign is?
#area = norm(cross(v1, v2))
##if area < 0.0000000001*max((norm(v1),norm(v2))):
#if area < 0.:
# area *= -1.
alpha = np.arctan2(norm(cross(v1, v2)), dot(v1, v2))
#print v1
#print v2
#print alpha
#print ''
normalSum += face.normal * alpha
n = normalize(normalSum)
return n
@property
@cacheGeometry
def cotan(self):
"""
element type : halfedge
Compute the cotangent of
the angle OPPOSITE this halfedge.
This is not directly required,
but will be useful
when computing the mean curvature
normals below.
This method gets called
on a halfedge,
so 'self' is a reference to the
halfedge at which we will compute the cotangent.
https://math.stackexchange.com/questions/2041099/
angle-between-vectors-given-cross-and-dot-product
see half edge here:
Users/lukemcculloch/Documents/Coding/Python/
DifferentialGeometry/course-master/libddg_userguide.pdf
"""
if self.isReal:
# Relevant vectors
A = -self.next.vector
B = self.next.next.vector
# Nifty vector equivalent of cot(theta)
val = np.dot(A, B) / norm(cross(A, B))
return val
else:
return 0.0
@property
@cacheGeometry
def vertex_Laplace(self):
"""
element type : vertex
Compute a vertex normal
using the 'mean curvature' method.
del del phi = 2NH
-picked up negative sign due to
cross products pointing into the page?
-no they are normalized.
-picked up a negative sign due to
the cotan(s) being defined
for pj, instead of pi.
But how did it change anything?
SwissArmyLaplacian.pdf, page 147
Applying 'L' to a column bector u
implements the cotan formula
M = [square diagonal]
"""
hl = list(self.adjacentHalfEdges())
pi = self.position
sumj = 0.
ot = 1. / 3.
for hlfedge in hl:
pj = hlfedge.vertex.position
ct1 = hlfedge.cotan
ct2 = hlfedge.twin.cotan
sumj += (ct1 + ct2) * (pj - pi)
#laplace = .5*sumj
return normalize(.5 * sumj)
@property
@cacheGeometry
def vertexNormal_MeanCurvature(self):
"""
element type : vertex
Compute a vertex normal
using the 'mean curvature' method.
Be sure to understand
the relationship between
this method and the
area gradient method.
aka, http://brickisland.net/cs177/?p=217:
(the remarkable fact is that the most
straightforward discretization of laplacian
leads us right back to the cotan formula! I
n other words, the vertex normals we get from
the mean curvature vector are precisely
the same as the ones we get from the area gradient.)
p 60 siggraph2013
del del phi = 2NH
This method gets called
on a vertex, so 'self' is a reference to the
vertex at which we will compute the normal.
http://brickisland.net/cs177/?p=309
For the dual area of a vertex
you can simply use one-third
the area of the incident faces
hl[0].next.next.next is hl[0]
>>> True
hl[0].twin.twin is hl[0]
>>> True
"""
hl = list(self.adjacentHalfEdges())
# lenhl = len(hl)
#
# for hlfedge in self.adjacentHalfEdges:
# pass.
pi = self.position
sumj = 0.
ot = 1. / 3.
for hlfedge in hl:
pj = hlfedge.vertex.position
#ct1 = hlfedge.next.cotan
ct2 = hlfedge.cotan
#ct2 = hlfedge.twin.next.cotan
ct1 = hlfedge.twin.cotan
#dual_area = -ot*hlfedge.face.area #wtf
sumj += (ct2 + ct1) * (pj - pi) #/dual_area
laplace = .5 * sumj
"""
Picked up a sign because?
-picked up negative sign due to
cross products pointing into the page?
-no they are normalized.
-picked up a negative sign due to
the cotan(s) being defined
for pj, instead of pi.
But how did it change anything?
"""
return normalize(laplace)
#return normalize(laplace*(.5/self.angleDefect))
@property
@cacheGeometry
def vertexNormal_SphereInscribed(self):
"""
element type : vertex
Compute a vertex normal
using the 'inscribed sphere' method.
This method gets called on a vertex,
so 'self' is a reference to the
vertex at which we will compute the normal.
normal at a vertex pi
can be expressed purely in terms of the
edge vectors
ej = pj-pi
where pj
are the immediate neighbors
of pi
"""
vl = list(self.adjacentVerts())
lenvl = len(vl)
vl.append(vl[0])
# Ns = Vector3D(0.0,0.0,0.0)
# for i in range(lenvl):
# v1 = vl[i].position
# v2 = vl[i+1].position
# e1 = v1 - self.position
# e2 = v2 - self.position
# Ns += cross(e1,e2)/((norm(e1)**2)*
# (norm(e2)**2))
hl = list(self.adjacentHalfEdges())
lenhl = len(hl)
hl.append(hl[0])
Ns = Vector3D(0.0, 0.0, 0.0)
for i in range(lenhl):
e1 = hl[i].vector
e2 = hl[i + 1].vector
#Ns += cross(e1,e2)/(sum(abs(e1)**2)*
# sum(abs(e2)**2))
Ns += cross(e1, e2) / ((norm(e1)**2) * (norm(e2)**2))
return normalize(-Ns)
#return Vector3D(0.0,0.0,0.0) # placeholder value
@property
@cacheGeometry
def angleDefect(self):
"""
angleDefect <=> local Gaussian Curvature
element type : vertex
Compute the angle defect of a vertex,
d(v) (see Assignment 1 Exercise 8).
This method gets called on a vertex,
so 'self' is a reference to the
vertex at which we will compute the angle defect.
"""
"""
el = list(self.adjacentEdges())
evpl = list(self.adjacentEdgeVertexPairs())
fl = list(self.adjacentFaces())
vl = list(self.adjacentVerts())
https://scicomp.stackexchange.com/questions/27689/
numerically-stable-way-of-computing-angles-between-vectors
#"""
hl = list(self.adjacentHalfEdges())
lenhl = len(hl)
hl.append(hl[0])
alpha = 0.
for i in range(lenhl):
v1 = hl[i].vector
v2 = hl[i + 1].vector
alpha += np.arctan2(norm(cross(v1, v2)), dot(v1, v2))
#dv = 2.*np.pi - alpha
return 2. * np.pi - alpha
def totalGaussianCurvature():
"""
Compute the total Gaussian curvature
in the mesh,
meaning the sum of Gaussian
curvature at each vertex.
Note that you can access
the mesh with the 'mesh' variable.
"""
tot = 0.
for vel in mesh.verts:
tot += vel.angleDefect
return tot
def gaussianCurvatureFromGaussBonnet():
"""
Compute the total Gaussian curvature
that the mesh should have, given that the
Gauss-Bonnet theorem holds
(see Assignment 1 Exercise 9).
Note that you can access
the mesh with the 'mesh' variable.
The mesh includes members like
'mesh.verts' and 'mesh.faces', which are
sets of the vertices (resp. faces) in the mesh.
"""
V = len(mesh.verts)
E = len(mesh.edges)
F = len(mesh.faces)
EulerChar = V - E + F
return 2. * np.pi * EulerChar
###################### END YOUR CODE
# Set these newly-defined methods
# as the methods to use in the classes
Face.normal = faceNormal
Face.area = faceArea
Vertex.normal = vertexNormal_AreaWeighted
Vertex.vertexNormal_EquallyWeighted = vertexNormal_EquallyWeighted
Vertex.vertexNormal_AreaWeighted = vertexNormal_AreaWeighted
Vertex.vertexNormal_AngleWeighted = vertexNormal_AngleWeighted
Vertex.vertexNormal_MeanCurvature = vertexNormal_MeanCurvature
#
Vertex.vertex_Laplace = vertex_Laplace
#
Vertex.vertexNormal_SphereInscribed = vertexNormal_SphereInscribed
Vertex.angleDefect = angleDefect
HalfEdge.cotan = cotan
if show:
## Functions which will be called
# by keypresses to visualize these definitions
def toggleFaceVectors():
print("\nToggling vertex vector display")
if toggleFaceVectors.val:
toggleFaceVectors.val = False
meshDisplay.setVectors(None)
else:
toggleFaceVectors.val = True
meshDisplay.setVectors('normal', vectorDefinedAt='face')
meshDisplay.generateVectorData()
toggleFaceVectors.val = False # ridiculous Python scoping hack
meshDisplay.registerKeyCallback(
'1',
toggleFaceVectors,
docstring="Toggle drawing face normal vectors")
def toggleVertexVectors():
print("\nToggling vertex vector display")
if toggleVertexVectors.val:
toggleVertexVectors.val = False
meshDisplay.setVectors(None)
else:
toggleVertexVectors.val = True
meshDisplay.setVectors('normal', vectorDefinedAt='vertex')
meshDisplay.generateVectorData()
toggleVertexVectors.val = False # ridiculous Python scoping hack
meshDisplay.registerKeyCallback(
'2',
toggleVertexVectors,
docstring="Toggle drawing vertex normal vectors")
def toggleDefect():
print("\nToggling angle defect display")
if toggleDefect.val:
toggleDefect.val = False
meshDisplay.setShapeColorToDefault()
else:
toggleDefect.val = True
meshDisplay.setShapeColorFromScalar("angleDefect",
cmapName="seismic")
# vMinMax=[-pi/8,pi/8])
meshDisplay.generateFaceData()
toggleDefect.val = False
meshDisplay.registerKeyCallback(
'3',
toggleDefect,
docstring="Toggle drawing angle defect coloring")
def useEquallyWeightedNormals():
mesh.staticGeometry = False
print("\nUsing equally-weighted normals")
Vertex.normal = vertexNormal_EquallyWeighted
mesh.staticGeometry = True
meshDisplay.generateAllMeshValues()
meshDisplay.registerKeyCallback(
'4',
useEquallyWeightedNormals,
docstring="Use equally-weighted normal computation")
def useAreaWeightedNormals():
mesh.staticGeometry = False
print("\nUsing area-weighted normals")
Vertex.normal = vertexNormal_AreaWeighted
mesh.staticGeometry = True
meshDisplay.generateAllMeshValues()
meshDisplay.registerKeyCallback(
'5',
useAreaWeightedNormals,
docstring="Use area-weighted normal computation")
def useAngleWeightedNormals():
mesh.staticGeometry = False
print("\nUsing angle-weighted normals")
Vertex.normal = vertexNormal_AngleWeighted
mesh.staticGeometry = True
meshDisplay.generateAllMeshValues()
meshDisplay.registerKeyCallback(
'6',
useAngleWeightedNormals,
docstring="Use angle-weighted normal computation")
def useMeanCurvatureNormals():
mesh.staticGeometry = False
print("\nUsing mean curvature normals")
Vertex.normal = vertexNormal_MeanCurvature
mesh.staticGeometry = True
meshDisplay.generateAllMeshValues()
meshDisplay.registerKeyCallback(
'7',
useMeanCurvatureNormals,
docstring="Use mean curvature normal computation")
def useSphereInscribedNormals():
mesh.staticGeometry = False
print("\nUsing sphere-inscribed normals")
Vertex.normal = vertexNormal_SphereInscribed
mesh.staticGeometry = True
meshDisplay.generateAllMeshValues()
meshDisplay.registerKeyCallback(
'8',
useSphereInscribedNormals,
docstring="Use sphere-inscribed normal computation")
def computeDiscreteGaussBonnet():
print("\nComputing total curvature:")
computed = totalGaussianCurvature()
predicted = gaussianCurvatureFromGaussBonnet()
print(" Total computed curvature: " + str(computed))
print(" Predicted value from Gauss-Bonnet is: " + str(predicted))
print(" Error is: " + str(abs(computed - predicted)))
meshDisplay.registerKeyCallback('z',
computeDiscreteGaussBonnet,
docstring="Compute total curvature")
def deformShape():
print("\nDeforming shape")
mesh.staticGeometry = False
# Get the center and scale of the shape
center = meshDisplay.dataCenter
scale = meshDisplay.scaleFactor
# Rotate according to swirly function
ax = eu.Vector3(-1.0, .75, 0.5)
for v in mesh.verts:
vec = v.position - center
theta = 0.8 * norm(vec) / scale
newVec = np.array(eu.Vector3(*vec).rotate_around(ax, theta))
v.position = center + newVec
mesh.staticGeometry = True
meshDisplay.generateAllMeshValues()
meshDisplay.registerKeyCallback(
'x',
deformShape,
docstring="Apply a swirly deformation to the shape")
## Register pick functions that output useful information on click
def pickVert(vert):
print(" Position:" + printVec3(vert.position))
print(" Angle defect: {:.5f}".format(vert.angleDefect))
print(" Normal (equally weighted): " +
printVec3(vert.vertexNormal_EquallyWeighted))
print(" Normal (area weighted): " +
printVec3(vert.vertexNormal_AreaWeighted))
print(" Normal (angle weighted): " +
printVec3(vert.vertexNormal_AngleWeighted))
print(" Normal (sphere-inscribed): " +
printVec3(vert.vertexNormal_SphereInscribed))
print(" Normal (mean curvature): " +
printVec3(vert.vertexNormal_MeanCurvature))
meshDisplay.pickVertexCallback = pickVert
def pickFace(face):
print(" Face area: {:.5f}".format(face.area))
print(" Normal: " + printVec3(face.normal))
print(" Vertex positions: ")
for (i, vert) in enumerate(face.adjacentVerts()):
print(" v{}: {}".format((i + 1), printVec3(vert.position)))
meshDisplay.pickFaceCallback = pickFace
# Start the viewer running
if show:
meshDisplay.startMainLoop()
return mesh
def main():
# Get the path for the mesh to load, either from the program argument if
# one was given, or a dialog otherwise
if(len(sys.argv) > 1):
filename = sys.argv[1]
else:
print("ERROR: No file name specified. Proper syntax is 'python Assignment2.py path/to/your/mesh.obj'.")
exit()
# Read in the mesh
mesh = HalfEdgeMesh(readMesh(filename))
# Create a viewer object
winName = 'DDG Assignment2 -- ' + os.path.basename(filename)
meshDisplay = MeshDisplay(windowTitle=winName, width=400, height=300)
meshDisplay.setMesh(mesh)
###################### BEGIN YOUR CODE
# implement the body of each of these functions
@property
@cacheGeometry
def faceArea(self):
"""
Compute the area of a face. Though not directly requested, this will be
useful when computing face-area weighted normals below.
This method gets called on a face, so 'self' is a reference to the
face at which we will compute the area.
"""
v = list(self.adjacentVerts())
a = 0.5 * norm(cross(v[1].position - v[0].position, v[2].position - v[0].position))
return a
def faceArea2(self):
"""
use area vector to compute the polygon area
"""
sum_areavector = [0.0, 0.0, 0.0]
verts = list(self.adjacentVerts())
LEN = len(verts)
for (i, v) in enumerate(verts):
sum_areavector += 0.5 * cross(verts[i].position, verts[(i+1)%LEN].position)
return norm(sum_areavector)
@property
@cacheGeometry
def faceNormal(self):
"""
Compute normal at a face of the mesh. Unlike at vertices, there is one very
obvious way to do this, since a face uniquely defines a plane.
This method gets called on a face, so 'self' is a reference to the
face at which we will compute the normal.
"""
v = list(self.adjacentVerts())
n = normalize(cross(v[1].position - v[0].position, v[2].position - v[0].position))
return n
@property
@cacheGeometry
def vertexNormal_EquallyWeighted(self):
"""
Compute a vertex normal using the 'equally weighted' method.
This method gets called on a vertex, so 'self' is a reference to the
vertex at which we will compute the normal.
"""
normalSum = np.array([0.0,0.0,0.0])
for face in self.adjacentFaces():
normalSum += face.normal * 1.0
n = normalize(normalSum)
return n
@property
@cacheGeometry
def vertexNormal_AreaWeighted(self):
"""
Compute a vertex normal using the 'face area weights' method.
This method gets called on a vertex, so 'self' is a reference to the
vertex at which we will compute the normal.
"""
normalSum = np.array([0.0,0.0,0.0])
for face in self.adjacentFaces():
normalSum += face.normal * face.area
n = normalize(normalSum)
return n
@property
@cacheGeometry
def vertexNormal_AngleWeighted(self):
"""
Compute a vertex normal using the 'tip angle weights' method.
This method gets called on a vertex, so 'self' is a reference to the
vertex at which we will compute the normal.
"""
normalSum = np.array([0.0,0.0,0.0])
for face in self.adjacentFaces():
v = list(face.adjacentVerts())
v0 = v1 = v2 = Vertex()
if v[0].id == self.id:
v0 = v[0]; v1 = v[1]; v2 = v[2];
if v[1].id == self.id:
v0 = v[1]; v1 = v[2]; v2 = v[0];
if v[2].id == self.id:
v0 = v[2]; v1 = v[0]; v2 = v[1];
a = v1.position - v0.position
b = v2.position - v0.position
theta = acos(np.dot((a/norm(a)),(b/norm(b))))
normalSum += face.normal * theta
n = normalize(normalSum)
return n
#@property
#@cacheGeometry
def cotan(self):
"""
Compute the cotangent of the angle opposite a halfedge. This is not
directly required, but will be useful when computing the mean curvature
normals below.
This method gets called on a halfedge, so 'self' is a reference to the
halfedge at which we will compute the cotangent.
"""
if self.next.next.next is not self:
raise ValueError("ERROR: halfedge.cotan() is only well-defined on a triangle")
if self.isReal:
# Relevant vectors
v0 = self.next.next.vector
v1 = -self.next.vector
# Nifty vector equivalent of cot(theta)
val = np.dot(v0, v1) / norm(cross(v0, v1))
return val
else:
return 0.0 # placeholder value
@property
@cacheGeometry
def vertexNormal_MeanCurvature(self):
"""
Compute a vertex normal using the 'mean curvature' method.
Be sure to understand the relationship between this method and the
area gradient method.
This method gets called on a vertex, so 'self' is a reference to the
vertex at which we will compute the normal.
"""
# the vertex normals we get from the mean curvature vector are precisely
# the same as the ones we get from the area gradient
# areaGrad(p_i) = 0.5 * SUM((cot a_j + cot b_j)(p_i - p_j))
sum_normal = [0.0, 0.0, 0.0]
halfedges = list(self.adjacentHalfEdges_CounterClockwise())
for he in halfedges:
sum_normal += (cotan(he.twin) + cotan(he)) * (-he.vector) # (p_i - p_j) = -he.vector
n = normalize(0.5 * sum_normal)
return n
@property
@cacheGeometry
def vertexNormal_SphereInscribed(self):
"""
Compute a vertex normal using the 'inscribed sphere' method.
This method gets called on a vertex, so 'self' is a reference to the
vertex at which we will compute the normal.
"""
# Ns = 1/c * SUM(e(j) x e(j+1) / (|e(j)|^2 * |e(j+1)|^2))
sum_normal = [0.0, 0.0, 0.0]
halfedges = list(self.adjacentHalfEdges_CounterClockwise())
LEN = len(halfedges)
for j in range(0, LEN-1): # [0, LEN-1)
normj = norm(halfedges[j].vector)
normj1 = norm(halfedges[j+1].vector)
sum_normal += cross(halfedges[j].vector, halfedges[j+1].vector) / (normj*normj * normj1*normj1)
n = normalize(sum_normal)
return n # But it seems that I should use -n to return the correct normal value
@property
@cacheGeometry
def angleDefect(self):
"""
Compute the angle defect of a vertex, d(v) (see Assignment 1 Exercise 8).
This method gets called on a vertex, so 'self' is a reference to the
vertex at which we will compute the angle defect.
"""
sum_theta = 0.0
# acos(np.dot((a/norm(a)),(b/norm(b))))
for face in self.adjacentFaces():
v = list(face.adjacentVerts())
v0 = v1 = v2 = Vertex()
if v[0].id == self.id:
v0 = v[0]; v1 = v[1]; v2 = v[2];
if v[1].id == self.id:
v0 = v[1]; v1 = v[2]; v2 = v[0];
if v[2].id == self.id:
v0 = v[2]; v1 = v[0]; v2 = v[1];
a = v1.position - v0.position
b = v2.position - v0.position
theta = acos(np.dot((a/norm(a)),(b/norm(b))))
sum_theta += theta
return 2.0 * pi - sum_theta
def totalGaussianCurvature():
"""
Compute the total Gaussian curvature in the mesh, meaning the sum of Gaussian
curvature at each vertex.
Note that you can access the mesh with the 'mesh' variable.
"""
sum_ = 0.0
for v in mesh.verts:
sum_ += v.angleDefect
return sum_
def gaussianCurvatureFromGaussBonnet():
"""
Compute the total Gaussian curvature that the mesh should have, given that the
Gauss-Bonnet theorem holds (see Assignment 1 Exercise 9).
Note that you can access the mesh with the 'mesh' variable. The
mesh includes members like 'mesh.verts' and 'mesh.faces', which are
sets of the vertices (resp. faces) in the mesh.
"""
X = len(mesh.verts) - len(mesh.edges) + len(mesh.faces)
return 2.0 * pi * X
###################### END YOUR CODE
# Set these newly-defined methods as the methods to use in the classes
Face.normal = faceNormal
Face.area = faceArea
Vertex.normal = vertexNormal_AreaWeighted
Vertex.vertexNormal_EquallyWeighted = vertexNormal_EquallyWeighted
Vertex.vertexNormal_AreaWeighted = vertexNormal_AreaWeighted
Vertex.vertexNormal_AngleWeighted = vertexNormal_AngleWeighted
Vertex.vertexNormal_MeanCurvature = vertexNormal_MeanCurvature
Vertex.vertexNormal_SphereInscribed = vertexNormal_SphereInscribed
Vertex.angleDefect = angleDefect
HalfEdge.cotan = cotan
## Functions which will be called by keypresses to visualize these definitions
def toggleFaceVectors():
print("\nToggling vertex vector display")
if toggleFaceVectors.val:
toggleFaceVectors.val = False
meshDisplay.setVectors(None)
else:
toggleFaceVectors.val = True
meshDisplay.setVectors('normal', vectorDefinedAt='face')
meshDisplay.generateVectorData()
toggleFaceVectors.val = False # ridiculous Python scoping hack
meshDisplay.registerKeyCallback('1', toggleFaceVectors, docstring="Toggle drawing face normal vectors")
def toggleVertexVectors():
print("\nToggling vertex vector display")
if toggleVertexVectors.val:
toggleVertexVectors.val = False
meshDisplay.setVectors(None)
else:
toggleVertexVectors.val = True
meshDisplay.setVectors('normal', vectorDefinedAt='vertex')
meshDisplay.generateVectorData()
toggleVertexVectors.val = False # ridiculous Python scoping hack
meshDisplay.registerKeyCallback('2', toggleVertexVectors, docstring="Toggle drawing vertex normal vectors")
def toggleDefect():
print("\nToggling angle defect display")
if toggleDefect.val:
toggleDefect.val = False
meshDisplay.setShapeColorToDefault()
else:
toggleDefect.val = True
meshDisplay.setShapeColorFromScalar("angleDefect", cmapName="seismic",vMinMax=[-pi/8,pi/8])
meshDisplay.generateFaceData()
toggleDefect.val = False
meshDisplay.registerKeyCallback('3', toggleDefect, docstring="Toggle drawing angle defect coloring")
def useEquallyWeightedNormals():
mesh.staticGeometry = False
print("\nUsing equally-weighted normals")
Vertex.normal = vertexNormal_EquallyWeighted
mesh.staticGeometry = True
meshDisplay.generateAllMeshValues()
meshDisplay.registerKeyCallback('4', useEquallyWeightedNormals, docstring="Use equally-weighted normal computation")
def useAreaWeightedNormals():
mesh.staticGeometry = False
print("\nUsing area-weighted normals")
Vertex.normal = vertexNormal_AreaWeighted
mesh.staticGeometry = True
meshDisplay.generateAllMeshValues()
meshDisplay.registerKeyCallback('5', useAreaWeightedNormals, docstring="Use area-weighted normal computation")
def useAngleWeightedNormals():
mesh.staticGeometry = False
print("\nUsing angle-weighted normals")
Vertex.normal = vertexNormal_AngleWeighted
mesh.staticGeometry = True
meshDisplay.generateAllMeshValues()
meshDisplay.registerKeyCallback('6', useAngleWeightedNormals, docstring="Use angle-weighted normal computation")
def useMeanCurvatureNormals():
mesh.staticGeometry = False
print("\nUsing mean curvature normals")
Vertex.normal = vertexNormal_MeanCurvature
mesh.staticGeometry = True
meshDisplay.generateAllMeshValues()
meshDisplay.registerKeyCallback('7', useMeanCurvatureNormals, docstring="Use mean curvature normal computation")
def useSphereInscribedNormals():
mesh.staticGeometry = False
print("\nUsing sphere-inscribed normals")
Vertex.normal = vertexNormal_SphereInscribed
mesh.staticGeometry = True
meshDisplay.generateAllMeshValues()
meshDisplay.registerKeyCallback('8', useSphereInscribedNormals, docstring="Use sphere-inscribed normal computation")
def computeDiscreteGaussBonnet():
print("\nComputing total curvature:")
computed = totalGaussianCurvature()
predicted = gaussianCurvatureFromGaussBonnet()
print(" Total computed curvature: " + str(computed))
print(" Predicted value from Gauss-Bonnet is: " + str(predicted))
print(" Error is: " + str(abs(computed - predicted)))
meshDisplay.registerKeyCallback('z', computeDiscreteGaussBonnet, docstring="Compute total curvature")
def deformShape():
print("\nDeforming shape")
mesh.staticGeometry = False
# Get the center and scale of the shape
center = meshDisplay.dataCenter
scale = meshDisplay.scaleFactor
# Rotate according to swirly function
ax = eu.Vector3(-1.0,.75,0.5)
for v in mesh.verts:
vec = v.position - center
theta = 0.8 * norm(vec) / scale
newVec = np.array(eu.Vector3(*vec).rotate_around(ax, theta))
v.position = center + newVec
mesh.staticGeometry = True
meshDisplay.generateAllMeshValues()
meshDisplay.registerKeyCallback('x', deformShape, docstring="Apply a swirly deformation to the shape")
## Register pick functions that output useful information on click
def pickVert(vert):
print(" Position:" + printVec3(vert.position))
print(" Angle defect: {:.5f}".format(vert.angleDefect))
print(" Normal (equally weighted): " + printVec3(vert.vertexNormal_EquallyWeighted))
print(" Normal (area weighted): " + printVec3(vert.vertexNormal_AreaWeighted))
print(" Normal (angle weighted): " + printVec3(vert.vertexNormal_AngleWeighted))
print(" Normal (sphere-inscribed): " + printVec3(vert.vertexNormal_SphereInscribed))
print(" Normal (mean curvature): " + printVec3(vert.vertexNormal_MeanCurvature))
meshDisplay.pickVertexCallback = pickVert
def pickFace(face):
print(" Face area : {:.5f}".format(face.area))
print(" Face area2: {:.5f}".format(faceArea2(face)))
print(" Normal: " + printVec3(face.normal))
print(" Vertex positions: ")
for (i, vert) in enumerate(face.adjacentVerts()):
print(" v{}: {}".format((i+1),printVec3(vert.position)))
meshDisplay.pickFaceCallback = pickFace
# Start the viewer running
meshDisplay.startMainLoop()
def main(inputfile, show=False, StaticGeometry=False, partString='part1'):
# Get the path for the mesh to load from the program argument
if (len(sys.argv) == 3):
partString = sys.argv[1]
if partString not in ['part1', 'part2', 'part3']:
print(
"ERROR part specifier not recognized. Should be one of 'part1', 'part2', or 'part3'"
)
exit()
filename = sys.argv[2]
elif inputfile is not None:
filename = inputfile
else:
print(
"ERROR: Incorrect call syntax. Proper syntax is 'python Assignment3.py partN path/to/your/mesh.obj'."
)
exit()
# Read in the mesh
mesh = HalfEdgeMesh(readMesh(filename), staticGeometry=StaticGeometry)
# Create a viewer object
winName = 'DDG Assignment3 ' + partString + '-- ' + os.path.basename(
filename)
meshDisplay = MeshDisplay(windowTitle=winName)
meshDisplay.setMesh(mesh)
###################### BEGIN YOUR CODE
# implement the body of each of these functions
############################
# assignment 2 code:
############################
@property
@cacheGeometry
def faceArea(self):
"""
Compute the area of a face.
Though not directly requested, this will be
useful when computing face-area weighted normals below.
This method gets called on a face,
so 'self' is a reference to the
face at which we will compute the area.
"""
v = list(self.adjacentVerts())
a = 0.5 * norm(
cross(v[1].position - v[0].position,
v[2].position - v[0].position))
return a
@property
@cacheGeometry
def vertexNormal_EquallyWeighted(self):
"""
Compute a vertex normal using the 'equally weighted' method.
This method gets called on a vertex,
so 'self' is a reference to the
vertex at which we will compute the normal.
http://brickisland.net/cs177/?p=217
Perhaps the simplest way to get vertex normals
is to just add up the neighboring face normals:
"""
normalSum = np.array([0.0, 0.0, 0.0])
for face in self.adjacentFaces():
normalSum += face.normal
n = normalize(normalSum)
#issue:
# two different tessellations of the same geometry
# can produce very different vertex normals
return n
@property
@cacheGeometry
def vertexNormal_AreaWeighted(self):
"""
Compute a vertex normal using
the 'face area weights' method.
This method gets called on a vertex,
so 'self' is a reference to the
vertex at which we will compute the normal.
The area-weighted normal vector for this vertex"""
normalSum = np.array([0.0, 0.0, 0.0])
for face in self.adjacentFaces():
normalSum += face.normal * face.area
n = normalize(normalSum)
#print 'computed vertexNormal_AreaWeighted n = ',n
return n
@property
@cacheGeometry
def vertexNormal_AngleWeighted(self):
"""
element type : vertex
Compute a vertex normal using the
'Tip-Angle Weights' method.
This method gets called on a vertex,
so 'self' is a reference to the
vertex at which we will compute the normal.
A simple way to reduce dependence
on the tessellation is to weigh face normals
by their corresponding tip angles theta, i.e.,
the interior angles incident on the vertex of interest:
"""
normalSum = np.array([0.0, 0.0, 0.0])
for face in self.adjacentFaces():
vl = list(face.adjacentVerts())
vl.remove(self)
v1 = vl[0].position - self.position
v2 = vl[1].position - self.position
# norm ->no need for check:
# it doesn not matter what the sign is?
#area = norm(cross(v1, v2))
##if area < 0.0000000001*max((norm(v1),norm(v2))):
#if area < 0.:
# area *= -1.
alpha = np.arctan2(norm(cross(v1, v2)), dot(v1, v2))
#print v1
#print v2
#print alpha
#print ''
normalSum += face.normal * alpha
n = normalize(normalSum)
return n
@property
@cacheGeometry
def faceNormal(self):
"""
Compute normal at a face of the mesh.
Unlike at vertices, there is one very
obvious way to do this, since a face
uniquely defines a plane.
This method gets called on a face,
so 'self' is a reference to the
face at which we will compute the normal.
"""
v = list(self.adjacentVerts())
n = normalize(
cross(v[1].position - v[0].position,
v[2].position - v[0].position))
return n
@property
@cacheGeometry
def cotan(self):
"""
element type : halfedge
Compute the cotangent of
the angle OPPOSITE this halfedge.
This is not directly required,
but will be useful
when computing the mean curvature
normals below.
This method gets called
on a halfedge,
so 'self' is a reference to the
halfedge at which we will compute the cotangent.
https://math.stackexchange.com/questions/2041099/
angle-between-vectors-given-cross-and-dot-product
see half edge here:
Users/lukemcculloch/Documents/Coding/Python/
DifferentialGeometry/course-master/libddg_userguide.pdf
"""
# Validate that this is on a triangle
if self.next.next.next is not self:
raise ValueError(
"ERROR: halfedge.cotan() is only well-defined on a triangle")
if self.isReal:
# Relevant vectors
A = -self.next.vector
B = self.next.next.vector
# Nifty vector equivalent of cot(theta)
val = np.dot(A, B) / norm(cross(A, B))
return val
else:
return 0.0
@property
@cacheGeometry
def angleDefect(self):
"""
angleDefect <=> local Gaussian Curvature
element type : vertex
Compute the angle defect of a vertex,
d(v) (see Assignment 1 Exercise 8).
This method gets called on a vertex,
so 'self' is a reference to the
vertex at which we will compute the angle defect.
"""
"""
el = list(self.adjacentEdges())
evpl = list(self.adjacentEdgeVertexPairs())
fl = list(self.adjacentFaces())
vl = list(self.adjacentVerts())
https://scicomp.stackexchange.com/questions/27689/
numerically-stable-way-of-computing-angles-between-vectors
#"""
hl = list(self.adjacentHalfEdges())
lenhl = len(hl)
hl.append(hl[0])
alpha = 0.
for i in range(lenhl):
v1 = hl[i].vector
v2 = hl[i + 1].vector
alpha += np.arctan2(norm(cross(v1, v2)), dot(v1, v2))
#dv = 2.*np.pi - alpha
return 2. * np.pi - alpha
def totalGaussianCurvature():
"""
Compute the total Gaussian curvature
in the mesh,
meaning the sum of Gaussian
curvature at each vertex.
Note that you can access
the mesh with the 'mesh' variable.
"""
tot = 0.
for vel in mesh.verts:
tot += vel.angleDefect
return tot
def gaussianCurvatureFromGaussBonnet():
"""
Compute the total Gaussian curvature
that the mesh should have, given that the
Gauss-Bonnet theorem holds
(see Assignment 1 Exercise 9).
Note that you can access
the mesh with the 'mesh' variable.
The mesh includes members like
'mesh.verts' and 'mesh.faces', which are
sets of the vertices (resp. faces) in the mesh.
"""
V = len(mesh.verts)
E = len(mesh.edges)
F = len(mesh.faces)
EulerChar = V - E + F
return 2. * np.pi * EulerChar
############################
# Part 0: Helper functions #
############################
# Implement a few useful functions that you will want in the remainder of
# the assignment.
@property
@cacheGeometry
def cotanWeight(self):
"""
Return the cotangent weight for an edge. Since this gets called on
an edge, 'self' will be a reference to an edge.
This will be useful in the problems below.
Don't forget, everything you implemented for the last homework is now
available as part of the library (normals, areas, etc). (Moving forward,
Vertex.normal will mean area-weighted normals, unless otherwise specified)
"""
val = 0.0
if self.anyHalfEdge.isReal:
val += self.anyHalfEdge.cotan
if self.anyHalfEdge.twin.isReal:
val += self.anyHalfEdge.twin.cotan
val *= 0.5
return val
@property
@cacheGeometry
def vertex_Laplace(self):
"""
element type : vertex
Compute a vertex normal
using the 'mean curvature' method.
del del phi = 2NH
-picked up negative sign due to
cross products pointing into the page?
-no they are normalized.
-picked up a negative sign due to
the cotan(s) being defined
for pj, instead of pi.
But how did it change anything?
"""
hl = list(self.adjacentHalfEdges())
pi = self.position
sumj = 0.
ot = 1. / 3.
for hlfedge in hl:
pj = hlfedge.vertex.position
ct1 = hlfedge.cotan
ct2 = hlfedge.twin.cotan
sumj += (ct1 + ct2) * (pj - pi)
#laplace = .5*sumj
return normalize(-.5 * sumj)
##
##*******************************************************
##
@property
@cacheGeometry
def dualArea(self):
"""
Return the dual area associated with a vertex.
Since this gets called on
a vertex, 'self' will be a
reference to a vertex.
Recall that the dual area can be
defined as 1/3 the area of the surrounding
faces.
http://brickisland.net/DDGFall2017/
'the barycentric dual area associated
with a vertex i is equal to one-third the area
of all triangles ijk touching i.'
"""
fl = list(self.adjacentFaces())
area_star = 0.
for ff in fl:
area_star += ff.area / 3.
return area_star
def enumerateVertices(mesh):
"""
Assign a unique index from 0 to (N-1) to each vertex in the mesh. Should
return a dictionary containing mappings {vertex ==> index}.
You will want to use this function in your solutions below.
"""
# index_map = {}
# index = 0
# for vv in mesh.verts:
# index_map[vv] = index
# index += 1
return mesh.enumerateVertices
@property
@cacheGeometry
def adjacency(self):
index_map = enumerateVertices(self)
nrows = ncols = len(mesh.verts)
adjacency = np.zeros((nrows, ncols), int)
for vv in mesh.verts:
ith = index_map[vv]
avlist = list(vv.adjacentVerts())
for av in avlist:
jth = index_map[av]
adjacency[ith, jth] = 1
return adjacency
#################################
# Part 1: Dense Poisson Problem #
#################################
# Solve a Poisson problem on the mesh. The primary function here
# is solvePoissonProblem_dense(), it will get called when you run
# python Assignment3.py part1 /path/to/your/mesh.obj
# and specify density values with the mouse (the press space to solve).
#
# Note that this code will be VERY slow on large meshes, because it uses
# dense matrices.
def buildLaplaceMatrix_dense(mesh, index_map=None):
"""
Build a Laplace operator for the mesh, with a dense representation
'index' is a dictionary mapping {vertex ==> index}
TLM renamed to index_map
Returns the resulting matrix.
"""
if index_map is None:
# index_map = mesh.enumerateVertices()
index_map = enumerateVertices(mesh)
nrows = ncols = len(mesh.verts)
adjacency = np.zeros((nrows, ncols), int)
for vv in mesh.verts:
ith = index_map[vv]
avlist = list(vv.adjacentVerts())
for av in avlist:
jth = index_map[av]
adjacency[ith, jth] = 1
Laplacian = np.zeros((nrows, ncols), float)
for vi in mesh.verts:
ith = index_map[vi]
ll = list(vi.adjacentEdgeVertexPairs())
for edge, vj in ll:
jth = index_map[vj]
# Laplacian[ith,jth] = np.dot(vj.normal,
# edge.cotanWeight*(vj.position -
# vi.position)
# )
if ith == jth:
pass #Laplacian[ith,jth] = edge.cotanWeight
else:
Laplacian[ith, jth] = edge.cotanWeight
Laplacian[ith, ith] = -sum(Laplacian[ith])
return Laplacian
def buildMassMatrix_dense(mesh, index):
"""
Build a mass matrix for the mesh.
Returns the resulting matrix.
"""
nrows = ncols = len(mesh.verts)
#MassMatrix = np.zeros((nrows),float)
MassMatrix = np.zeros((nrows, ncols), float)
for i, vert in enumerate(mesh.verts):
#MassMatrix[i,i] = 1./vert.dualArea
MassMatrix[i, i] = vert.dualArea
return MassMatrix
def solvePoissonProblem_dense(mesh, densityValues):
"""
Solve a Poisson problem on the mesh. The results should be stored on the
vertices in a variable named 'solutionVal'. You will want to make use
of your buildLaplaceMatrix_dense() function from above.
densityValues is a dictionary mapping {vertex ==> value} that specifies
densities. The density is implicitly zero at every vertex not in this
dictionary.
When you run this program with 'python Assignment3.py part1 path/to/your/mesh.obj',
you will get to click on vertices to specify density conditions. See the
assignment document for more details.
"""
index_map = enumerateVertices(mesh)
L = buildLaplaceMatrix_dense(mesh, index_map)
M = buildMassMatrix_dense(mesh, index_map) #M <= 2D
rho = np.zeros((len(mesh.verts)), float)
for key in densityValues:
#index_val = index_map[key]
print 'key dual area = ', key.dualArea
rho[index_map[key]] = densityValues[key] #*key.dualArea
#
# SwissArmyLaplacian,
# page 179 Cu = Mf is better conditioned
sol_vec = np.linalg.solve(L, np.dot(M, rho))
#sparse attempts:
#sol_vec = linsolve.spsolve(L, rho)
#sol_vec = dsolve.spsolve(L, rho, use_umfpack=False)
#sol_vec = dsolve.spsolve(L, rho, use_umfpack=True)
for vert in mesh.verts:
key = index_map[vert]
#print 'TLM sol_vec = ',sol_vec[key]
vert.solutionVal = sol_vec[key]
if rho[key]:
vert.densityVal = rho[key]
else:
vert.densityVal = 0.
return
##################################
# Part 2: Sparse Poisson Problem #
##################################
# Solve a Poisson problem on the mesh. The primary function here
# is solvePoissonProblem_sparse(), it will get called when you run
# python Assignment3.py part2 /path/to/your/mesh.obj
# and specify density values with the mouse (the press space to solve).
#
# This will be very similar to the previous part. Be sure to see the wiki
# for notes about the nuances of sparse matrix computation. Now, your code
# should scale well to larger meshes!
def buildLaplaceMatrix_sparse(mesh, index_map=None):
"""
Build a laplace operator for the mesh, with a sparse representation.
This will be nearly identical to the dense method.
'index' is a dictionary mapping {vertex ==> index}
Returns the resulting sparse matrix.
"""
if index_map is None:
# index_map = mesh.enumerateVertices()
index_map = enumerateVertices(mesh)
nrows = ncols = len(mesh.verts)
adjacency = np.zeros((nrows, ncols), int)
for vv in mesh.verts:
ith = index_map[vv]
avlist = list(vv.adjacentVerts())
for av in avlist:
jth = index_map[av]
adjacency[ith, jth] = 1
Laplacian = np.zeros((nrows, ncols), float)
for vi in mesh.verts:
ith = index_map[vi]
ll = list(vi.adjacentEdgeVertexPairs())
for edge, vj in ll:
jth = index_map[vj]
# Laplacian[ith,jth] = np.dot(vj.normal,
# edge.cotanWeight*(vj.position -
# vi.position)
# )
if ith == jth:
pass #Laplacian[ith,jth] = edge.cotanWeight
else:
Laplacian[ith, jth] = edge.cotanWeight
Laplacian[ith, ith] = -sum(Laplacian[ith])
return csr_matrix(Laplacian)
def buildMassMatrix_sparse(mesh, index):
"""
Build a sparse mass matrix for the system.
Returns the resulting sparse matrix.
"""
nrows = ncols = len(mesh.verts)
MassMatrix = np.zeros((nrows), float)
#for i,vert in enumerate(mesh.verts):
# MassMatrix[i] = vert.dualArea
return MassMatrix
def solvePoissonProblem_sparse(mesh, densityValues):
"""
Solve a Poisson problem on the mesh, using sparse matrix operations.
This will be nearly identical to the dense method.
The results should be stored on the vertices in a variable named 'solutionVal'.
densityValues is a dictionary mapping {vertex ==> value} that specifies any
densities. The density is implicitly zero at every vertex not in this dictionary.
Note: Be sure to look at the notes on the github wiki about sparse matrix
computation in Python.
When you run this program with 'python Assignment3.py part2 path/to/your/mesh.obj',
you will get to click on vertices to specify density conditions. See the
assignment document for more details.
"""
index_map = enumerateVertices(mesh)
L = buildLaplaceMatrix_sparse(mesh, index_map)
M = buildMassMatrix_dense(mesh, index_map) #M <= 2D
rho = np.zeros((len(mesh.verts)), float)
for key in densityValues:
#index_val = index_map[key]
print 'key dual area = ', key.dualArea
rho[index_map[key]] = densityValues[key] #*key.dualArea
# convert to sparse matrix (CSR method)
#Lsparse = csr_matrix(L)
#iL = np.linalg.inv(L)
#sol_vec = np.dot(iL,rho)
#sol_vec = np.linalg.solve(L, rho)
#sol_vec = linsolve.spsolve(L, rho)
#sol_vec = linsolve.spsolve(L, np.dot(M,rho) )
#sol_vec = dsolve.spsolve(L, rho, use_umfpack=False)
sol_vec = dsolve.spsolve(L, np.dot(M, rho), use_umfpack=True)
for vert in mesh.verts:
key = index_map[vert]
#print 'TLM sol_vec = ',sol_vec[key]
vert.solutionVal = sol_vec[key]
if rho[key]:
vert.densityVal = rho[key]
else:
vert.densityVal = 0.
return
###############################
# Part 3: Mean Curvature Flow #
###############################
# Perform mean curvature flow on the mesh. The primary function here
# is meanCurvatureFlow(), which will get called when you run
# python Assignment3.py part3 /path/to/your/mesh.obj
# You can adjust the step size with the 'z' and 'x' keys, and press space
# to perform one step of flow.
#
# Of course, you will want to use sparse matrices here, so your code
# scales well to larger meshes.
def buildMeanCurvatureFlowOperator(mesh, index=None, h=None):
"""
Construct the (sparse) mean curvature operator matrix for the mesh.
It might be helpful to use your buildLaplaceMatrix_sparse() and
buildMassMatrix_sparse() methods from before.
Returns the resulting matrix.
"""
nrows = ncols = len(mesh.verts)
##MassMatrix = np.zeros((nrows),float)
#MassMatrix = np.zeros((nrows,ncols),float)
#for i,vert in enumerate(mesh.verts):
# MassMatrix[i] = 1./vert.dualArea
# #MassMatrix[i,i] = 1./vert.dualArea
Laplacian = np.zeros((nrows, ncols), float)
for vi in mesh.verts:
ith = index[vi]
ll = list(vi.adjacentEdgeVertexPairs())
for edge, vj in ll:
jth = index[vj]
# Laplacian[ith,jth] = np.dot(vj.normal,
# edge.cotanWeight*(vj.position -
# vi.position)
# )
if ith == jth:
pass #Laplacian[ith,jth] = edge.cotanWeight
else:
Laplacian[ith, jth] = edge.cotanWeight
Laplacian[ith, ith] = -sum(Laplacian[ith])
return csr_matrix(Laplacian)
def meanCurvatureFlow_use_numpy_solve(mesh, h):
"""
Perform mean curvature flow on the mesh. The result of this operation
is updated positions for the vertices; you should conclude by modifying
the position variables for the mesh vertices.
h is the step size for the backwards euler integration.
When you run this program with 'python Assignment3.py part3 path/to/your/mesh.obj',
you can press the space bar to perform this operation and z/x to change
the step size.
Recall that before you modify the positions of the mesh, you will need
to set mesh.staticGeometry = False, which disables caching optimizations
but allows you to modfiy the geometry. After you are done modfiying
positions, you should set mesh.staticGeometry = True to re-enable these
optimizations. You should probably have mesh.staticGeometry = True while
you assemble your operator, or it will be very slow.
"""
# index_map = mesh.enumerateVertices()
index_map = enumerateVertices(mesh)
nrows = ncols = len(mesh.verts)
Id = np.identity(nrows, float)
M = buildMassMatrix_dense(mesh, index_map) #M <= 2D
MCF = buildMeanCurvatureFlowOperator(mesh, index=index_map, h=h)
#
# SwissArmyLaplacian,
# page 181 (I-hC)u = u is not symmetric
# (M-hC)u = Mu is better conditioned
#----------------------------------------------
Mi = np.linalg.inv(M)
L = np.matmul(Mi, MCF)
#UpdateOperator = np.linalg.inv(Id-h*L)
#----------------------------------------------
#UpdateOperator = np.linalg.inv(M-h*MCF)
LHS = M - h * MCF
UpdateOperator = np.linalg.inv(LHS)
#UpdateOperator = np.matmul(UpdateOperator,M)
vertices = np.zeros((nrows, 3), float)
for i, vert in enumerate(mesh.verts):
vertices[i] = vert.position
LHS = Id - h * L
UpdateOperator = np.linalg.solve(LHS, vertices)
vertices = UpdateOperator
for i, vert in enumerate(mesh.verts):
#key = index_map[vert]
vert.position = vertices[i]
#
# vertices = np.dot(UpdateOperator,vertices)
# for i,vert in enumerate(mesh.verts):
# key = index_map[vert]
# vert.position = vertices[i]
return
def meanCurvatureFlow(mesh, h):
"""
Perform mean curvature flow on the mesh. The result of this operation
is updated positions for the vertices; you should conclude by modifying
the position variables for the mesh vertices.
h is the step size for the backwards euler integration.
When you run this program with 'python Assignment3.py part3 path/to/your/mesh.obj',
you can press the space bar to perform this operation and z/x to change
the step size.
Recall that before you modify the positions of the mesh, you will need
to set mesh.staticGeometry = False, which disables caching optimizations
but allows you to modfiy the geometry. After you are done modfiying
positions, you should set mesh.staticGeometry = True to re-enable these
optimizations. You should probably have mesh.staticGeometry = True while
you assemble your operator, or it will be very slow.
"""
# index_map = mesh.enumerateVertices()
index_map = enumerateVertices(mesh)
nrows = ncols = len(mesh.verts)
#Id = np.identity(nrows,float)
M = buildMassMatrix_dense(mesh, index_map) #M <= 2D
Msp = csr_matrix(M)
#pure cotan operator:
MCF = buildMeanCurvatureFlowOperator(mesh, index=index_map, h=h)
#
# SwissArmyLaplacian,
# page 181 (I-hC)u = u is not symmetric
# (M-hC)u = Mu is better conditioned
#----------------------------------------------
#Mi = np.linalg.inv(M)
#L = np.matmul(Mi,MCF)
#UpdateOperator = np.linalg.inv(Id-h*L)
#----------------------------------------------
#LHS = M-h*MCF
LHS = Msp - MCF.multiply(h)
#UpdateOperator = np.linalg.inv(LHS)
#UpdateOperator = np.matmul(UpdateOperator,M)
UpdateOperator = dsolve.spsolve(LHS, M, use_umfpack=True)
vertices = np.zeros((nrows, 3), float)
for i, vert in enumerate(mesh.verts):
vertices[i] = vert.position
#https://docs.scipy.org/doc/scipy-0.14.0/reference/generated/scipy.linalg.cho_solve.html
#UpdateOperator = scipy.linalg.cho_solve(
# scipy.linalg.cho_factor(LHS),
# np.dot(M,vertices))
#P, L, U = scipy.linalg.lu(LHS)
# for non symmetric, numpy solve, style:
# LHS = Id-h*L
# UpdateOperator = np.linalg.solve(LHS, vertices)
# vertices = UpdateOperator
# for i,vert in enumerate(mesh.verts):
# #key = index_map[vert]
# vert.position = vertices[i]
#
vertices = np.dot(UpdateOperator, vertices)
for i, vert in enumerate(mesh.verts):
#key = index_map[vert]
vert.position = vertices[i]
return
###################### END YOUR CODE
# from assignment 2:
Face.normal = faceNormal
Face.area = faceArea
Vertex.normal = vertexNormal_AreaWeighted
Vertex.vertexNormal_EquallyWeighted = vertexNormal_EquallyWeighted
Vertex.vertexNormal_AreaWeighted = vertexNormal_AreaWeighted
Vertex.vertexNormal_AngleWeighted = vertexNormal_AngleWeighted
##
Vertex.vertex_Laplace = vertex_Laplace
#
#Vertex.vertexNormal_SphereInscribed = vertexNormal_SphereInscribed
Vertex.angleDefect = angleDefect
HalfEdge.cotan = cotan
def toggleDefect():
print("\nToggling angle defect display")
if toggleDefect.val:
toggleDefect.val = False
meshDisplay.setShapeColorToDefault()
else:
toggleDefect.val = True
meshDisplay.setShapeColorFromScalar("angleDefect",
cmapName="seismic")
#,vMinMax=[-pi/8,pi/8])
meshDisplay.generateFaceData()
toggleDefect.val = False
meshDisplay.registerKeyCallback(
'3', toggleDefect, docstring="Toggle drawing angle defect coloring")
def computeDiscreteGaussBonnet():
print("\nComputing total curvature:")
computed = totalGaussianCurvature()
predicted = gaussianCurvatureFromGaussBonnet()
print(" Total computed curvature: " + str(computed))
print(" Predicted value from Gauss-Bonnet is: " + str(predicted))
print(" Error is: " + str(abs(computed - predicted)))
meshDisplay.registerKeyCallback('z',
computeDiscreteGaussBonnet,
docstring="Compute total curvature")
###################### Assignment 3 stuff
Edge.cotanWeight = cotanWeight
Vertex.dualArea = dualArea
# A pick function for choosing density conditions
densityValues = dict()
def pickVertBoundary(vert):
"""
See MeshDisplay callbacks,
pickVertexCallback
for how this works!
self.pickVertexCallback <== pickVertBoundary(vert)
self.pickVertexCallback(pickObject = your_vertex)
"""
value = 1.0 if pickVertBoundary.isHigh else -1.0
print(" Selected vertex at position:" + printVec3(vert.position))
print(" as a density with value = " + str(value))
densityValues[vert] = value
print 'densityValues = ', densityValues
pickVertBoundary.isHigh = not pickVertBoundary.isHigh
pickVertBoundary.isHigh = True
# Run in part1 mode
if partString == 'part1':
print("\n\n === Executing assignment 2 part 1")
print("""
Please click on vertices of the mesh to specify density conditions.
Alternating clicks will specify high-value (= 1.0) and low-value (= -1.0)
density conditions. You may select as many density vertices as you want,
but >= 2 are necessary to yield an interesting solution. When you are done,
press the space bar to execute your solver and view the results.
""")
meshDisplay.pickVertexCallback = pickVertBoundary
meshDisplay.drawVertices = True
def executePart1Callback():
print("\n=== Solving Poisson problem with your dense solver\n")
# Print and check the density values
print("Density values:")
for key in densityValues:
print(" " + str(key) + " = " + str(densityValues[key]))
#if len(densityValues) < 2:
# print("Aborting solve, not enough density vertices specified")
# return
# Call the solver
print("\nSolving problem...")
t0 = time.time()
solvePoissonProblem_dense(mesh, densityValues)
tSolve = time.time() - t0
print("...solution completed.")
print("Solution took {:.5f} seconds.".format(tSolve))
print("Visualizing results...")
# Error out intelligently if nothing is stored on vert.solutionVal
for vert in mesh.verts:
if not hasattr(vert, 'solutionVal'):
print(
"ERROR: At least one vertex does not have the attribute solutionVal defined."
)
exit()
if not isinstance(vert.solutionVal, float):
print(
"ERROR: The data stored at vertex.solutionVal is not of type float."
)
print(" The data has type=" +
str(type(vert.solutionVal)))
print(" The data looks like vert.solutionVal=" +
str(vert.solutionVal))
exit()
# Visualize the result
# meshDisplay.setShapeColorFromScalar("solutionVal",
# definedOn='vertex',
# cmapName="seismic",
# vMinMax=[-10.0,10.0])
meshDisplay.setShapeColorFromScalar("solutionVal",
definedOn='vertex',
cmapName="seismic")
meshDisplay.generateAllMeshValues()
meshDisplay.registerKeyCallback(
' ',
executePart1Callback,
docstring="Solve the Poisson problem and view the results")
def showdensity():
# Visualize the result
# meshDisplay.setShapeColorFromScalar("densityVal",
# definedOn='vertex',
# cmapName="seismic",
# vMinMax=[-1.0,1.0])
meshDisplay.setShapeColorFromScalar("densityVal",
definedOn='vertex',
cmapName="seismic")
meshDisplay.generateAllMeshValues()
meshDisplay.registerKeyCallback(
'b',
showdensity,
docstring="Show the density map for the Poisson Problem")
# Start the GUI
if show:
meshDisplay.startMainLoop()
# Run in part2 mode
elif partString == 'part2':
print("\n\n === Executing assignment 2 part 2")
print("""
Please click on vertices of the mesh to specify density conditions.
Alternating clicks will specify high-value (= 1.0) and low-value (= -1.0)
density conditions. You may select as many density vertices as you want,
but >= 2 are necessary to yield an interesting solution. When you are done,
press the space bar to execute your solver and view the results.
""")
meshDisplay.pickVertexCallback = pickVertBoundary
meshDisplay.drawVertices = True
def executePart2Callback():
print("\n=== Solving Poisson problem with your sparse solver\n")
# Print and check the density values
print("Density values:")
for key in densityValues:
print(" " + str(key) + " = " + str(densityValues[key]))
#if len(densityValues) < 2:
# print("Aborting solve, not enough density vertices specified")
# return
# Call the solver
print("\nSolving problem...")
t0 = time.time()
solvePoissonProblem_sparse(mesh, densityValues)
tSolve = time.time() - t0
print("...solution completed.")
print("Solution took {:.5f} seconds.".format(tSolve))
print("Visualizing results...")
# Error out intelligently if nothing is stored on vert.solutionVal
for vert in mesh.verts:
if not hasattr(vert, 'solutionVal'):
print(
"ERROR: At least one vertex does not have the attribute solutionVal defined."
)
exit()
if not isinstance(vert.solutionVal, float):
print(
"ERROR: The data stored at vertex.solutionVal is not of type float."
)
print(" The data has type=" +
str(type(vert.solutionVal)))
print(" The data looks like vert.solutionVal=" +
str(vert.solutionVal))
exit()
# Visualize the result
# meshDisplay.setShapeColorFromScalar("solutionVal", definedOn='vertex', cmapName="seismic", vMinMax=[-1.0,1.0])
meshDisplay.setShapeColorFromScalar("solutionVal",
definedOn='vertex',
cmapName="seismic")
meshDisplay.generateAllMeshValues()
meshDisplay.registerKeyCallback(
' ',
executePart2Callback,
docstring="Solve the Poisson problem and view the results")
# Start the GUI
if show:
meshDisplay.startMainLoop()
# Run in part3 mode
elif partString == 'part3':
print("\n\n === Executing assignment 2 part 3")
print("""
Press the space bar to perform one step of mean curvature
flow smoothing, using your solver. Pressing the 'z' and 'x'
keys will decrease and increase the step size (h), respectively.
""")
stepSize = [0.01]
def increaseStepsize():
stepSize[0] += 0.001
print("Increasing step size. New size h=" + str(stepSize[0]))
def decreaseStepsize():
stepSize[0] -= 0.001
print("Decreasing step size. New size h=" + str(stepSize[0]))
meshDisplay.registerKeyCallback(
'z',
decreaseStepsize,
docstring="Increase the value of the step size (h) by 0.1")
meshDisplay.registerKeyCallback(
'x',
increaseStepsize,
docstring="Decrease the value of the step size (h) by 0.1")
def smoothingStep():
print("\n=== Performing mean curvature smoothing step\n")
print(" Step size h=" + str(stepSize[0]))
# Call the solver
print(" Solving problem...")
t0 = time.time()
meanCurvatureFlow(mesh, stepSize[0])
tSolve = time.time() - t0
print(" ...solution completed.")
print(" Solution took {:.5f} seconds.".format(tSolve))
print("Updating display...")
meshDisplay.generateAllMeshValues()
meshDisplay.registerKeyCallback(
' ',
smoothingStep,
docstring="Perform one step of your mean curvature flow on the mesh"
)
# Start the GUI
if show:
meshDisplay.startMainLoop()
return mesh, meshDisplay
def main():
# Get the path for the mesh to load, either from the program argument if
# one was given, or a dialog otherwise
if (len(sys.argv) > 1):
filename = sys.argv[1]
else:
print(
"ERROR: No file name specified. Proper syntax is 'python Assignment2.py path/to/your/mesh.obj'."
)
exit()
# Read in the mesh
mesh = HalfEdgeMesh(readMesh(filename))
# Create a viewer object
winName = 'DDG Assignment2 -- ' + os.path.basename(filename)
meshDisplay = MeshDisplay(windowTitle=winName)
meshDisplay.setMesh(mesh)
###################### BEGIN YOUR CODE
# implement the body of each of these functions
@property
@cacheGeometry
def faceArea(self):
"""
Compute the area of a face. Though not directly requested, this will be
useful when computing face-area weighted normals below.
This method gets called on a face, so 'self' is a reference to the
face at which we will compute the area.
"""
return 0.0 # placeholder value
@property
@cacheGeometry
def faceNormal(self):
"""
Compute normal at a face of the mesh. Unlike at vertices, there is one very
obvious way to do this, since a face uniquely defines a plane.
This method gets called on a face, so 'self' is a reference to the
face at which we will compute the normal.
"""
return Vector3D(0.0, 0.0, 0.0) # placeholder value
@property
@cacheGeometry
def vertexNormal_EquallyWeighted(self):
"""
Compute a vertex normal using the 'equally weighted' method.
This method gets called on a vertex, so 'self' is a reference to the
vertex at which we will compute the normal.
"""
return Vector3D(0.0, 0.0, 0.0) # placeholder value
@property
@cacheGeometry
def vertexNormal_AreaWeighted(self):
"""
Compute a vertex normal using the 'face area weights' method.
This method gets called on a vertex, so 'self' is a reference to the
vertex at which we will compute the normal.
"""
return Vector3D(0.0, 0.0, 0.0) # placeholder value
@property
@cacheGeometry
def vertexNormal_AngleWeighted(self):
"""
Compute a vertex normal using the 'tip angle weights' method.
This method gets called on a vertex, so 'self' is a reference to the
vertex at which we will compute the normal.
"""
return Vector3D(0.0, 0.0, 0.0) # placeholder value
@property
@cacheGeometry
def cotan(self):
"""
Compute the cotangent of the angle opposite a halfedge. This is not
directly required, but will be useful when computing the mean curvature
normals below.
This method gets called on a halfedge, so 'self' is a reference to the
halfedge at which we will compute the cotangent.
"""
return 0.0 # placeholder value
@property
@cacheGeometry
def vertexNormal_MeanCurvature(self):
"""
Compute a vertex normal using the 'mean curvature' method.
Be sure to understand the relationship between this method and the
area gradient method.
This method gets called on a vertex, so 'self' is a reference to the
vertex at which we will compute the normal.
"""
return Vector3D(0.0, 0.0, 0.0) # placeholder value
@property
@cacheGeometry
def vertexNormal_SphereInscribed(self):
"""
Compute a vertex normal using the 'inscribed sphere' method.
This method gets called on a vertex, so 'self' is a reference to the
vertex at which we will compute the normal.
"""
return Vector3D(0.0, 0.0, 0.0) # placeholder value
@property
@cacheGeometry
def angleDefect(self):
"""
Compute the angle defect of a vertex, d(v) (see Assignment 1 Exercise 8).
This method gets called on a vertex, so 'self' is a reference to the
vertex at which we will compute the angle defect.
"""
return 0.0 # placeholder value
def totalGaussianCurvature():
"""
Compute the total Gaussian curvature in the mesh, meaning the sum of Gaussian
curvature at each vertex.
Note that you can access the mesh with the 'mesh' variable.
"""
return 0.0 # placeholder value
def gaussianCurvatureFromGaussBonnet():
"""
Compute the total Gaussian curvature that the mesh should have, given that the
Gauss-Bonnet theorem holds (see Assignment 1 Exercise 9).
Note that you can access the mesh with the 'mesh' variable. The
mesh includes members like 'mesh.verts' and 'mesh.faces', which are
sets of the vertices (resp. faces) in the mesh.
"""
return 0.0 # placeholder value
###################### END YOUR CODE
# Set these newly-defined methods as the methods to use in the classes
Face.normal = faceNormal
Face.area = faceArea
Vertex.normal = vertexNormal_AreaWeighted
Vertex.vertexNormal_EquallyWeighted = vertexNormal_EquallyWeighted
Vertex.vertexNormal_AreaWeighted = vertexNormal_AreaWeighted
Vertex.vertexNormal_AngleWeighted = vertexNormal_AngleWeighted
Vertex.vertexNormal_MeanCurvature = vertexNormal_MeanCurvature
Vertex.vertexNormal_SphereInscribed = vertexNormal_SphereInscribed
Vertex.angleDefect = angleDefect
HalfEdge.cotan = cotan
## Functions which will be called by keypresses to visualize these definitions
def toggleFaceVectors():
print("\nToggling vertex vector display")
if toggleFaceVectors.val:
toggleFaceVectors.val = False
meshDisplay.setVectors(None)
else:
toggleFaceVectors.val = True
meshDisplay.setVectors('normal', vectorDefinedAt='face')
meshDisplay.generateVectorData()
toggleFaceVectors.val = False # ridiculous Python scoping hack
meshDisplay.registerKeyCallback(
'1', toggleFaceVectors, docstring="Toggle drawing face normal vectors")
def toggleVertexVectors():
print("\nToggling vertex vector display")
if toggleVertexVectors.val:
toggleVertexVectors.val = False
meshDisplay.setVectors(None)
else:
toggleVertexVectors.val = True
meshDisplay.setVectors('normal', vectorDefinedAt='vertex')
meshDisplay.generateVectorData()
toggleVertexVectors.val = False # ridiculous Python scoping hack
meshDisplay.registerKeyCallback(
'2',
toggleVertexVectors,
docstring="Toggle drawing vertex normal vectors")
def toggleDefect():
print("\nToggling angle defect display")
if toggleDefect.val:
toggleDefect.val = False
meshDisplay.setShapeColorToDefault()
else:
toggleDefect.val = True
meshDisplay.setShapeColorFromScalar("angleDefect",
cmapName="seismic",
vMinMax=[-pi / 8, pi / 8])
meshDisplay.generateFaceData()
toggleDefect.val = False
meshDisplay.registerKeyCallback(
'3', toggleDefect, docstring="Toggle drawing angle defect coloring")
def useEquallyWeightedNormals():
mesh.staticGeometry = False
print("\nUsing equally-weighted normals")
Vertex.normal = vertexNormal_EquallyWeighted
mesh.staticGeometry = True
meshDisplay.generateAllMeshValues()
meshDisplay.registerKeyCallback(
'4',
useEquallyWeightedNormals,
docstring="Use equally-weighted normal computation")
def useAreaWeightedNormals():
mesh.staticGeometry = False
print("\nUsing area-weighted normals")
Vertex.normal = vertexNormal_AreaWeighted
mesh.staticGeometry = True
meshDisplay.generateAllMeshValues()
meshDisplay.registerKeyCallback(
'5',
useAreaWeightedNormals,
docstring="Use area-weighted normal computation")
def useAngleWeightedNormals():
mesh.staticGeometry = False
print("\nUsing angle-weighted normals")
Vertex.normal = vertexNormal_AngleWeighted
mesh.staticGeometry = True
meshDisplay.generateAllMeshValues()
meshDisplay.registerKeyCallback(
'6',
useAngleWeightedNormals,
docstring="Use angle-weighted normal computation")
def useMeanCurvatureNormals():
mesh.staticGeometry = False
print("\nUsing mean curvature normals")
Vertex.normal = vertexNormal_MeanCurvature
mesh.staticGeometry = True
meshDisplay.generateAllMeshValues()
meshDisplay.registerKeyCallback(
'7',
useMeanCurvatureNormals,
docstring="Use mean curvature normal computation")
def useSphereInscribedNormals():
mesh.staticGeometry = False
print("\nUsing sphere-inscribed normals")
Vertex.normal = vertexNormal_SphereInscribed
mesh.staticGeometry = True
meshDisplay.generateAllMeshValues()
meshDisplay.registerKeyCallback(
'8',
useSphereInscribedNormals,
docstring="Use sphere-inscribed normal computation")
def computeDiscreteGaussBonnet():
print("\nComputing total curvature:")
computed = totalGaussianCurvature()
predicted = gaussianCurvatureFromGaussBonnet()
print(" Total computed curvature: " + str(computed))
print(" Predicted value from Gauss-Bonnet is: " + str(predicted))
print(" Error is: " + str(abs(computed - predicted)))
meshDisplay.registerKeyCallback('z',
computeDiscreteGaussBonnet,
docstring="Compute total curvature")
def deformShape():
print("\nDeforming shape")
mesh.staticGeometry = False
# Get the center and scale of the shape
center = meshDisplay.dataCenter
scale = meshDisplay.scaleFactor
# Rotate according to swirly function
ax = eu.Vector3(-1.0, .75, 0.5)
for v in mesh.verts:
vec = v.position - center
theta = 0.8 * norm(vec) / scale
newVec = np.array(eu.Vector3(*vec).rotate_around(ax, theta))
v.position = center + newVec
mesh.staticGeometry = True
meshDisplay.generateAllMeshValues()
meshDisplay.registerKeyCallback(
'x', deformShape, docstring="Apply a swirly deformation to the shape")
## Register pick functions that output useful information on click
def pickVert(vert):
print(" Position:" + printVec3(vert.position))
print(" Angle defect: {:.5f}".format(vert.angleDefect))
print(" Normal (equally weighted): " +
printVec3(vert.vertexNormal_EquallyWeighted))
print(" Normal (area weighted): " +
printVec3(vert.vertexNormal_AreaWeighted))
print(" Normal (angle weighted): " +
printVec3(vert.vertexNormal_AngleWeighted))
print(" Normal (sphere-inscribed): " +
printVec3(vert.vertexNormal_SphereInscribed))
print(" Normal (mean curvature): " +
printVec3(vert.vertexNormal_MeanCurvature))
meshDisplay.pickVertexCallback = pickVert
def pickFace(face):
print(" Face area: {:.5f}".format(face.area))
print(" Normal: " + printVec3(face.normal))
print(" Vertex positions: ")
for (i, vert) in enumerate(face.adjacentVerts()):
print(" v{}: {}".format((i + 1), printVec3(vert.position)))
meshDisplay.pickFaceCallback = pickFace
# Start the viewer running
meshDisplay.startMainLoop()
def main():
# Get the path for the mesh to load, either from the program argument if
# one was given, or a dialog otherwise
if len(sys.argv) > 1:
filename = sys.argv[1]
else:
print("ERROR: No file name specified. Proper syntax is 'python Assignment2.py path/to/your/mesh.obj'.")
exit()
# Read in the mesh
mesh = HalfEdgeMesh(readMesh(filename))
# Create a viewer object
winName = "DDG Assignment2 -- " + os.path.basename(filename)
meshDisplay = MeshDisplay(windowTitle=winName)
meshDisplay.setMesh(mesh)
###################### BEGIN YOUR CODE
# implement the body of each of these functions
@property
@cacheGeometry
def faceArea(self):
"""
Compute the area of a face. Though not directly requested, this will be
useful when computing face-area weighted normals below.
This method gets called on a face, so 'self' is a reference to the
face at which we will compute the area.
"""
return 0.0 # placeholder value
@property
@cacheGeometry
def faceNormal(self):
"""
Compute normal at a face of the mesh. Unlike at vertices, there is one very
obvious way to do this, since a face uniquely defines a plane.
This method gets called on a face, so 'self' is a reference to the
face at which we will compute the normal.
"""
return Vector3D(0.0, 0.0, 0.0) # placeholder value
@property
@cacheGeometry
def vertexNormal_EquallyWeighted(self):
"""
Compute a vertex normal using the 'equally weighted' method.
This method gets called on a vertex, so 'self' is a reference to the
vertex at which we will compute the normal.
"""
return Vector3D(0.0, 0.0, 0.0) # placeholder value
@property
@cacheGeometry
def vertexNormal_AreaWeighted(self):
"""
Compute a vertex normal using the 'face area weights' method.
This method gets called on a vertex, so 'self' is a reference to the
vertex at which we will compute the normal.
"""
return Vector3D(0.0, 0.0, 0.0) # placeholder value
@property
@cacheGeometry
def vertexNormal_AngleWeighted(self):
"""
Compute a vertex normal using the 'tip angle weights' method.
This method gets called on a vertex, so 'self' is a reference to the
vertex at which we will compute the normal.
"""
return Vector3D(0.0, 0.0, 0.0) # placeholder value
@property
@cacheGeometry
def cotan(self):
"""
Compute the cotangent of the angle opposite a halfedge. This is not
directly required, but will be useful when computing the mean curvature
normals below.
This method gets called on a halfedge, so 'self' is a reference to the
halfedge at which we will compute the cotangent.
"""
return 0.0 # placeholder value
@property
@cacheGeometry
def vertexNormal_MeanCurvature(self):
"""
Compute a vertex normal using the 'mean curvature' method.
Be sure to understand the relationship between this method and the
area gradient method.
This method gets called on a vertex, so 'self' is a reference to the
vertex at which we will compute the normal.
"""
return Vector3D(0.0, 0.0, 0.0) # placeholder value
@property
@cacheGeometry
def vertexNormal_SphereInscribed(self):
"""
Compute a vertex normal using the 'inscribed sphere' method.
This method gets called on a vertex, so 'self' is a reference to the
vertex at which we will compute the normal.
"""
return Vector3D(0.0, 0.0, 0.0) # placeholder value
@property
@cacheGeometry
def angleDefect(self):
"""
Compute the angle defect of a vertex, d(v) (see Assignment 1 Exercise 8).
This method gets called on a vertex, so 'self' is a reference to the
vertex at which we will compute the angle defect.
"""
return 0.0 # placeholder value
def totalGaussianCurvature():
"""
Compute the total Gaussian curvature in the mesh, meaning the sum of Gaussian
curvature at each vertex.
Note that you can access the mesh with the 'mesh' variable.
"""
return 0.0 # placeholder value
def gaussianCurvatureFromGaussBonnet():
"""
Compute the total Gaussian curvature that the mesh should have, given that the
Gauss-Bonnet theorem holds (see Assignment 1 Exercise 9).
Note that you can access the mesh with the 'mesh' variable. The
mesh includes members like 'mesh.verts' and 'mesh.faces', which are
sets of the vertices (resp. faces) in the mesh.
"""
return 0.0 # placeholder value
###################### END YOUR CODE
# Set these newly-defined methods as the methods to use in the classes
Face.normal = faceNormal
Face.area = faceArea
Vertex.normal = vertexNormal_AreaWeighted
Vertex.vertexNormal_EquallyWeighted = vertexNormal_EquallyWeighted
Vertex.vertexNormal_AreaWeighted = vertexNormal_AreaWeighted
Vertex.vertexNormal_AngleWeighted = vertexNormal_AngleWeighted
Vertex.vertexNormal_MeanCurvature = vertexNormal_MeanCurvature
Vertex.vertexNormal_SphereInscribed = vertexNormal_SphereInscribed
Vertex.angleDefect = angleDefect
HalfEdge.cotan = cotan
## Functions which will be called by keypresses to visualize these definitions
def toggleFaceVectors():
print("\nToggling vertex vector display")
if toggleFaceVectors.val:
toggleFaceVectors.val = False
meshDisplay.setVectors(None)
else:
toggleFaceVectors.val = True
meshDisplay.setVectors("normal", vectorDefinedAt="face")
meshDisplay.generateVectorData()
toggleFaceVectors.val = False # ridiculous Python scoping hack
meshDisplay.registerKeyCallback("1", toggleFaceVectors, docstring="Toggle drawing face normal vectors")
def toggleVertexVectors():
print("\nToggling vertex vector display")
if toggleVertexVectors.val:
toggleVertexVectors.val = False
meshDisplay.setVectors(None)
else:
toggleVertexVectors.val = True
meshDisplay.setVectors("normal", vectorDefinedAt="vertex")
meshDisplay.generateVectorData()
toggleVertexVectors.val = False # ridiculous Python scoping hack
meshDisplay.registerKeyCallback("2", toggleVertexVectors, docstring="Toggle drawing vertex normal vectors")
def toggleDefect():
print("\nToggling angle defect display")
if toggleDefect.val:
toggleDefect.val = False
meshDisplay.setShapeColorToDefault()
else:
toggleDefect.val = True
meshDisplay.setShapeColorFromScalar("angleDefect", cmapName="seismic", vMinMax=[-pi / 8, pi / 8])
meshDisplay.generateFaceData()
toggleDefect.val = False
meshDisplay.registerKeyCallback("3", toggleDefect, docstring="Toggle drawing angle defect coloring")
def useEquallyWeightedNormals():
mesh.staticGeometry = False
print("\nUsing equally-weighted normals")
Vertex.normal = vertexNormal_EquallyWeighted
mesh.staticGeometry = True
meshDisplay.generateAllMeshValues()
meshDisplay.registerKeyCallback("4", useEquallyWeightedNormals, docstring="Use equally-weighted normal computation")
def useAreaWeightedNormals():
mesh.staticGeometry = False
print("\nUsing area-weighted normals")
Vertex.normal = vertexNormal_AreaWeighted
mesh.staticGeometry = True
meshDisplay.generateAllMeshValues()
meshDisplay.registerKeyCallback("5", useAreaWeightedNormals, docstring="Use area-weighted normal computation")
def useAngleWeightedNormals():
mesh.staticGeometry = False
print("\nUsing angle-weighted normals")
Vertex.normal = vertexNormal_AngleWeighted
mesh.staticGeometry = True
meshDisplay.generateAllMeshValues()
meshDisplay.registerKeyCallback("6", useAngleWeightedNormals, docstring="Use angle-weighted normal computation")
def useMeanCurvatureNormals():
mesh.staticGeometry = False
print("\nUsing mean curvature normals")
Vertex.normal = vertexNormal_MeanCurvature
mesh.staticGeometry = True
meshDisplay.generateAllMeshValues()
meshDisplay.registerKeyCallback("7", useMeanCurvatureNormals, docstring="Use mean curvature normal computation")
def useSphereInscribedNormals():
mesh.staticGeometry = False
print("\nUsing sphere-inscribed normals")
Vertex.normal = vertexNormal_SphereInscribed
mesh.staticGeometry = True
meshDisplay.generateAllMeshValues()
meshDisplay.registerKeyCallback("8", useSphereInscribedNormals, docstring="Use sphere-inscribed normal computation")
def computeDiscreteGaussBonnet():
print("\nComputing total curvature:")
computed = totalGaussianCurvature()
predicted = gaussianCurvatureFromGaussBonnet()
print(" Total computed curvature: " + str(computed))
print(" Predicted value from Gauss-Bonnet is: " + str(predicted))
print(" Error is: " + str(abs(computed - predicted)))
meshDisplay.registerKeyCallback("z", computeDiscreteGaussBonnet, docstring="Compute total curvature")
def deformShape():
print("\nDeforming shape")
mesh.staticGeometry = False
# Get the center and scale of the shape
center = meshDisplay.dataCenter
scale = meshDisplay.scaleFactor
# Rotate according to swirly function
ax = eu.Vector3(-1.0, 0.75, 0.5)
for v in mesh.verts:
vec = v.position - center
theta = 0.8 * norm(vec) / scale
newVec = np.array(eu.Vector3(*vec).rotate_around(ax, theta))
v.position = center + newVec
mesh.staticGeometry = True
meshDisplay.generateAllMeshValues()
meshDisplay.registerKeyCallback("x", deformShape, docstring="Apply a swirly deformation to the shape")
## Register pick functions that output useful information on click
def pickVert(vert):
print(" Position:" + printVec3(vert.position))
print(" Angle defect: {:.5f}".format(vert.angleDefect))
print(" Normal (equally weighted): " + printVec3(vert.vertexNormal_EquallyWeighted))
print(" Normal (area weighted): " + printVec3(vert.vertexNormal_AreaWeighted))
print(" Normal (angle weighted): " + printVec3(vert.vertexNormal_AngleWeighted))
print(" Normal (sphere-inscribed): " + printVec3(vert.vertexNormal_SphereInscribed))
print(" Normal (mean curvature): " + printVec3(vert.vertexNormal_MeanCurvature))
meshDisplay.pickVertexCallback = pickVert
def pickFace(face):
print(" Face area: {:.5f}".format(face.area))
print(" Normal: " + printVec3(face.normal))
print(" Vertex positions: ")
for (i, vert) in enumerate(face.adjacentVerts()):
print(" v{}: {}".format((i + 1), printVec3(vert.position)))
meshDisplay.pickFaceCallback = pickFace
# Start the viewer running
meshDisplay.startMainLoop()