def externalEnergy(self, controlpoints):
"""
Returns the external energy of the snake. The external energy is computed
via the provided ExternalEnergy subclass object. The external energy is
the sum of the external energies at each control point which get multiplied
by the inverse of the number of control points.
"""
# compute the factor the energy of each control points get's weighed with
external = 0.0
if len(self.controlpoints) > 0:
factor = float(1)/len(self.controlpoints)
else:
factor = 1
# check if the given controlpoints are equal to the current ones
if np.equal(controlpoints, self.controlpoints).all():
# take the current normals
normals = self.normals
else:
# otherwise calculate the according normals
spline = Spline()
spline.addControlPoints(*controlpoints)
normals = spline.normals
# ACHTUNG! hier müssen die Normalen zur Berechnung gedreht werden,
# falls flip es vorgibt
if self.flip:
normals = map(lambda n: rotateVector(n, angle=pi), normals)
# only remember each external control point energy if the given control points are
# the snakes current control points
memorize_energies = np.equal(controlpoints, self.controlpoints).all()
# reset the controlpointenergy list if necessary
if memorize_energies:
self.ext_energies = []
# sum up the energies at the single control points multiplied by the inverse
# of the number of control points
for i in range(len(controlpoints)):
point = controlpoints[i]
# if len(normals) > 0:
# normal = normals[i]
# else:
# normal = None
normal = normals[i]
pointenergy = self.ExternalEnergy.getEnergy(point, iteration=self.iteration, normal=normal)
# check wether to save the point energy
if memorize_energies:
#self.ext_energies.append(self.ExternalEnergy.getEnergy(point))
self.ext_energies.append(pointenergy)
external += pointenergy * factor
return external
def update(self):
"""
Recomputes energies and the contour, e.g. after a control point has
been added.
"""
# compute the contour and normals
spline = Spline()
spline.addControlPoints(*self.controlpoints)
lencontrolpoints = len(self.controlpoints)
self.contour = spline.interpolation
self.normals = spline.normals
# the following is not needed anymore
#if self.flip:
# self.normals = map(lambda n: rotateVector(n, angle=pi), self.normals)
# compute the energies
self.spacing = self.spacingEnergy(self.controlpoints)
self.curvature = self.curvatureEnergy(self.controlpoints)
self.external = self.externalEnergy(self.controlpoints)
self.energy = self.totalEnergy(self.controlpoints)
# compute the contour gradient for displaying the curvature energies
self.contour_gradient = contourCurvatureGradient(self.contour,
self.controlpoints,
self.crv_energies)
# check for saneness
if lencontrolpoints == 1 or lencontrolpoints == 0:
assert self.contour == []
assert self.spacing == 0.0
assert self.curvature == 0.0
elif lencontrolpoints == 0:
assert self.external == 0.0
assert len(self.normals) == []
elif lencontrolpoints > 1:
assert len(self.contour) > 0
assert lencontrolpoints == len(self.normals)
assert lencontrolpoints == len(self.ext_energies), '%s != %s' % (len(self.controlpoints), len(self.ext_energies))
