[SOLVED] Using Python to move some points or parts of an object

[baymin]

Hi,

I want to use python to move some points of an object, which function should I use?

I have tried applyTranslation(x,y,z) of Sofa.BaseMechanicalState but it did not work. I have also tried setting value of Sofa.Data but it did not work too.

If there are something wrong in the setting?

def createGraph(self,rootNode):
	gravity = '0 0 0'
        # rootNode
        rootNode.createObject('VisualStyle', displayFlags='showForceFields')
        rootNode.createObject('DefaultPipeline', name='CollisionPipeline', verbose='0')
        rootNode.createObject('BruteForceDetection', name='N2')
        rootNode.createObject('DefaultContactManager', name='collision response', response='default')
        rootNode.createObject('DiscreteIntersection')

        # rootNode/LiverFEM
        LiverFEM = rootNode.createChild('LiverFEM')
        self.LiverFEM = LiverFEM
        LiverFEM.gravity = gravity
        LiverFEM.createObject('EulerImplicitSolver', printLog='0', rayleighStiffness='0.1', name='cg_odesolver', rayleighMass='0.1')
        LiverFEM.createObject('CGLinearSolver', threshold='1e-09', tolerance='1e-09', name='linear solver', iterations='25')
        LiverFEM.createObject('MeshTopology', name='mesh', fileTopology='mesh/liver.msh')
        LiverFEM.createObject('MechanicalObject', name='dofs', template='Vec3d')
        LiverFEM.createObject('TetrahedronFEMForceField', youngModulus='50', name='FEM', poissonRatio='0.45', template='Vec3d')
        LiverFEM.createObject('UniformMass', name='mass', totalmass='1')
        LiverFEM.createObject('FixedConstraint', indices='3 39 64', name='FixedConstraint')

        # rootNode/LiverFEM/Visu
        Visu = LiverFEM.createChild('Visu')
        self.Visu = Visu
        Visu.gravity = gravity
        Visu.createObject('OglModel', name='VisualModel', fileMesh='mesh/liver-smooth.obj')
        Visu.createObject('BarycentricMapping', input='@../dofs', name='visual mapping', output='@VisualModel')

        # rootNode/LiverFEM/Surf
        Surf = LiverFEM.createChild('Surf')
        self.Surf = Surf
        Surf.gravity = gravity
        Surf.createObject('SphereLoader', name='SphereLoader', filename='mesh/liver.sph')
        Surf.createObject('MechanicalObject', position='@[-1].position', name='mappedMS')
        Surf.createObject('SphereModel', listRadius='@[-2].listRadius', name='CollisionModel')
        Surf.createObject('BarycentricMapping', input='@../dofs', name='sphere mapping', output='@mappedMS')

best,

Baymin

[Hugo]

Hi @baymin

There is actually several ways of enforcing displacement:

– You could first use the component LinearMovementConstraint (see example scene in examples/Components/constraint/LinearMovementConstraint.scn): with this component you can impose a sequential linear movement between target positions

– another option is to create another MechanicalObject with your moving target positions and define springs between these nodes and your object

There is maybe other ways that I am forgetting, but the above-mentioned ones can be easily tested. I hope this helps.

Hugo

[baymin]

Dear Hugo,

Thank you very much for your help.
Both using ‘PartialLinearMovementConstraint’ and adding springs between nodes are work well.

Best,

Baymin

[baymin]

Hi, @Hugo

How can I change the position of some points of an object in real-time.
I tried to use ‘PartialLinearMovementConstraint’ and set the properties: ‘movements’ and ‘keyTimes’:

self.LiverFEM.getObject('PartialLinearMovementConstraint').findData('keyTimes').value = [[0.0], [5.0], [10.0]]
if self.count == t1: self.LiverFEM.getObject('PartialLinearMovementConstraint').findData('movements').value = [[0, 0, 0], [0.1, -0.1, -0.1], [0.1, -0.1, -0.1]]
elif self.count == t2:
   self.LiverFEM.getObject('PartialLinearMovementConstraint').findData('movements').value = [[0, 0, 0], [0.1, -0.1, -0.1], [-0.1, 0.1, 0.1]]

but the object in simulation changed suddenly and did not move smoothly as set it in the createGraph function/method:

LiverFEM.createObject('PartialLinearMovementConstraint', indices='100 105 110', keyTimes='0 5 10', template='Vec3d', movements='0 0 0  0.1 -0.1 -0.1 -0.1 0.1 0.1')

So how can I change the position of one point of an object such as one blue point on the surface in each AnimationStep?

https://drive.google.com/file/d/13wC1e5j2eSSdgBaMD8ywH4tSdkJlbSSY/view?usp=sharing

Best,

Baymin

[baymin]

Hi,

I have moved some points of an object in real-time success, by adding the below code into the function ‘onBeginAnimationStep’:

cT = self.LiverFEM.getTime()
self.LiverFEM.getObject('PartialLinearMovementConstraint').findData('keyTimes').value = [[cT], [cT + 100]]
self.LiverFEM.getObject('PartialLinearMovementConstraint').findData('movements').value = [0.5*math.sin(cT), 0.5*math.cos(cT), 0]

But what is the meaning of the keyTimes? If I set it too small, the simulation will illness. On the other hand, if I set it biger, it works well, but 1s, 10s and 100s has nothing different.

Best,

Baymin

[Author]

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