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Full force field example in Python #642

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Full force field example in Python #642

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97d7907
Full force field example in Python
alxbilger Oct 12, 2026
00bfe6f
fix stiffness parameter
alxbilger Oct 13, 2026
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46 changes: 29 additions & 17 deletions examples/example-forcefield.py
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Original file line number Diff line number Diff line change
Expand Up @@ -14,19 +14,24 @@ def __init__(self, ks=1.0, kd=1.0, *args, **kwargs):
def init(self):
mstate = self.getContext().mechanical
self.initpos = mstate.position.array().copy()
self.k = np.zeros((1,1))
self.f = []
self.d = 0.5

def addForce(self, m, out_force, pos, vel):
with out_force.writeableArray() as wa:
wa[:] += ( (self.initpos-pos.value) * self.ks.value )

def addDForce(self, params, df, dx):
pass

#def addKToMatrix(self, params, number_of_nodes, number_of_dofs_per_node):
# print(" Python::addKToMatrix: ", a, " ", b)
kFactor = params['kFactor']
with df.writeableArray() as dfwa:
dfwa[:] -= dx.value * self.ks.value * kFactor

def addKToMatrix(self, params, number_of_nodes, number_of_dofs_per_node):
K = []
kFactor = params['kFactor']
for n in range(0, number_of_nodes):
for d in range(0, number_of_dofs_per_node):
K.append([number_of_dofs_per_node * n + d, number_of_dofs_per_node * n + d, -kFactor * self.ks.value])
return np.asarray(K)



def createScene(root):
Expand All @@ -42,17 +47,24 @@ def createScene(root):

root.addObject("LineAxis")
root.addObject("DefaultAnimationLoop", name="loop")
root.addObject("EulerImplicitIntegrationScheme")
root.addObject("CGLinearSolver", tolerance=1e-12, threshold=1e-12, iterations=25)

o = root.addChild("Object")
c = o.addObject("MechanicalObject", name="mechanical", position=[0.0,0.0,0.0, 1.0,0.0,0.0])
c.showObject = True
c.showColor = [1.0,0.0,0.0,1.0]
c.drawMode = 1
def add_spring_simulation(node, start_position, color):
node.addObject("EulerImplicitIntegrationScheme", rayleighStiffness=0.1, rayleighMass=0.1)

o = node.addChild("Object")
c = o.addObject("MechanicalObject", name="mechanical", position=[start_position + 0.0,0.0,0.0, start_position + 1.0,0.0,0.0], showColor=color)
c.showObject = True
c.drawMode = 1

o.addObject("UniformMass", name="mass", totalMass=[0.1])
o.addObject( RestShapeForceField(name="spring", ks=2.0, kd=0.1))

o.addObject("UniformMass", name="mass", totalMass=[0.1])
o.addObject( RestShapeForceField(name="CPPObject", ks=2.0, kd=0.1))
with root.addChild("Direct") as direct:
add_spring_simulation(direct, 0.0, [0,1,0,1])
direct.addObject("SparseLDLSolver", template="CompressedRowSparseMatrixd")
with root.addChild("Iterative") as iterative:
add_spring_simulation(iterative, 0.2, [1,0,0,1])
iterative.addObject("CGLinearSolver", tolerance=1e-12, threshold=1e-12, iterations=25)

return root

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