def compute_inertia_and_center_of_mass(shapes, io=None):
"""
Compute inertia from a list of Shapes.
Returns
-------
mass
center_of_mass
inertia
inertia_matrix
"""
from OCC.GProp import GProp_GProps
from OCC.BRepGProp import brepgprop_VolumeProperties
from OCC.gp import gp_Ax1, gp_Dir
from siconos.mechanics import occ
system = GProp_GProps()
for shape in shapes:
iprops = GProp_GProps()
if shape.data is None:
if io is not None:
shape.data = io._shape.get(shape.shape_name, new_instance=True)
else:
warn('cannot get shape {0}'.format(shape.shape_name))
return None
iishape = shape.data
ishape = occ.OccContactShape(iishape).data()
# the shape relative displacement
occ.occ_move(ishape, list(shape.translation) + list(shape.orientation))
brepgprop_VolumeProperties(iishape, iprops)
density = None
if hasattr(shape, 'mass') and shape.mass is not None:
density = shape.mass / iprops.Mass()
elif shape.parameters is not None and hasattr(shape.parameters,
'density'):
density = shape.parameters.density
#print('shape.parameters.density:', shape.parameters.density)
else:
density = 1.
assert density is not None
# print("shape", shape.shape_name)
# print('density:', density)
# print('iprops.Mass():', iprops.Mass())
system.Add(iprops, density)
mass = system.Mass()
assert (system.Mass() > 0.)
computed_com = system.CentreOfMass()
gp_mat = system.MatrixOfInertia()
inertia_matrix = np.zeros((3, 3))
for i in range(0, 3):
for j in range(0, 3):
inertia_matrix[i, j] = gp_mat.Value(i + 1, j + 1)
I1 = system.MomentOfInertia(gp_Ax1(computed_com, gp_Dir(1, 0, 0)))
I2 = system.MomentOfInertia(gp_Ax1(computed_com, gp_Dir(0, 1, 0)))
I3 = system.MomentOfInertia(gp_Ax1(computed_com, gp_Dir(0, 0, 1)))
inertia = [I1, I2, I3]
center_of_mass = np.array(
[computed_com.Coord(1),
computed_com.Coord(2),
computed_com.Coord(3)])
return mass, center_of_mass, inertia, inertia_matrix
def compute_inertia_and_center_of_mass(shapes, mass, io=None):
"""
Compute inertia from a list of Shapes.
"""
from OCC.GProp import GProp_GProps
from OCC.BRepGProp import brepgprop_VolumeProperties
from OCC.gp import gp_Ax1, gp_Dir
from siconos.mechanics import occ
props = GProp_GProps()
for shape in shapes:
iprops = GProp_GProps()
if shape.data is None:
if io is not None:
shape.data = io._shape.get(shape.shape_name, new_instance=True)
else:
warn('cannot get shape {0}'.format(shape.shape_name))
return None
iishape = shape.data
ishape = occ.OccContactShape(iishape).data()
# the shape relative displacement
occ.occ_move(ishape, list(shape.translation) + list(shape.orientation))
brepgprop_VolumeProperties(iishape, iprops)
density = None
if hasattr(shape, 'mass') and shape.mass is not None:
density = shape.mass / iprops.Mass()
elif shape.parameters is not None and \
hasattr(shape.parameters, 'density'):
density = shape.parameters.density
else:
density = 1.
assert density is not None
props.Add(iprops, density)
assert (props.Mass() > 0.)
global_density = mass / props.Mass()
computed_com = props.CentreOfMass()
I1 = global_density * props.MomentOfInertia(
gp_Ax1(computed_com, gp_Dir(1, 0, 0)))
I2 = global_density * props.MomentOfInertia(
gp_Ax1(computed_com, gp_Dir(0, 1, 0)))
I3 = global_density * props.MomentOfInertia(
gp_Ax1(computed_com, gp_Dir(0, 0, 1)))
inertia = [I1, I2, I3]
center_of_mass = np.array(
[computed_com.Coord(1),
computed_com.Coord(2),
computed_com.Coord(3)])
return inertia, center_of_mass