class ShapeProps(object):
"""
Base class for shape properties.
"""
def __init__(self):
self._props = GProp_GProps()
@property
def mass(self):
"""
:return: The mass of the shape. This corresponds to total length for
linear properties, total area for surface properties, or total
volume for volume properties.
:rtype: float
"""
return self._props.Mass()
@property
def cg(self):
"""
:return: The center of gravity.
:rtype: afem.geometry.entities.Point
"""
gp_pnt = self._props.CentreOfMass()
return Point(gp_pnt.X(), gp_pnt.Y(), gp_pnt.Z())
@property
def static_moments(self):
"""
:return: The static moments of inertia Ix, Iy, and Iz.
:rtype: tuple(float)
"""
return self._props.StaticMoments(0., 0., 0.)
@property
def matrix_of_inertia(self):
"""
:return: The 3 x 3 matrix of inertia.
:rtype: numpy.ndarray
"""
gp_mat = self._props.MatrixOfInertia()
matrix = []
for j in range(1, 4):
row = []
for i in range(1, 4):
row.append(gp_mat.Value(i, j))
matrix.append(row)
return array(matrix, dtype=float)
def moment_of_inertia(self, axis):
"""
Compute the moment of inertia about the axis.
:param afem.geometry.entities.Axis1 axis: The axis.
:return: The moment of inertia.
:rtype: float
"""
return self._props.MomentOfInertia(axis)
def cube_inertia_properties():
""" Compute the inertia properties of a shape
"""
# Create and display cube
print("Creating a cubic box shape (50*50*50)")
cube_shape = BRepPrimAPI_MakeBox(50., 50., 50.).Shape()
# Compute inertia properties
props = GProp_GProps()
brepgprop_VolumeProperties(cube_shape, props)
# Get inertia properties
mass = props.Mass()
cog = props.CentreOfMass()
matrix_of_inertia = props.MatrixOfInertia()
# Display inertia properties
print("Cube mass = %s" % mass)
cog_x, cog_y, cog_z = cog.Coord()
print("Center of mass: x = %f;y = %f;z = %f;" % (cog_x, cog_y, cog_z))
print("Matrix of inertia", matrix_of_inertia)