Collision issue in my scene

[CaroPeltier]

Hello,

I am trying to simulate a candy moving inside the mouth, between the tongue (that I eventually want to control) and a tooth. The candy is initially placed on the tongue and should move along with it, while being blocked by the tooth.

At the moment, I am testing the setup with the tongue not controlled (no imposed motion, only gravity to test collision). However, I noticed that the tongue goes through the candy but is correctly stopped by the tooth.

Do you know why the tongue is not colliding with the candy, while collisions with the tooth are working as expected?

Thanks a lot for your help!

Caroline

PS: Sorry, curiously I was not able to attach my mesh files, I don't know why ?

import Sofa.Gui
import numpy as np

def main():
# Call the SOFA function to create the root node
    root = Sofa.Core.Node("root")
    # Call the createScene function, as runSofa does
    createScene(root)
    # Once defined, initialization of the scene graph
    Sofa.Simulation.init(root) # or Sofa.SimulationinitRoot(rootNode)
# Example of animation loop without GUI
#    for iteration in range 10):
#        Sofa.Simulation.animate(rootNode,rootNode.dt.value)
#           print("Iteration ", iteration, " Time : ", iteration*rootNode.dt.value, "s")
   
    # Launch the GUI (qt or qglviewer)
    Sofa.Gui.GUIManager.Init("myscene", "qglviewer") # imgui (qglviewer that is maintained)
    Sofa.Gui.GUIManager.createGUI(root, __file__)
    Sofa.Gui.GUIManager.SetDimension(1080, 800)
    # Initialization of the scene will be done here
    Sofa.Gui.GUIManager.MainLoop(root)
    Sofa.Gui.GUIManager.closeGUI()

class MoveTongueController(Sofa.Core.Controller):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.mo = kwargs.get("MechanicalObject")  # récupère le MechanicalObject
        self.amplitude = 1500.0   # amplitude du mouvement (en mm si ton mesh est en mm)
        self.period = 3.0       # secondes

    def onAnimateBeginEvent(self, event):       
        root = self.getContext().getRootContext()
        t = root.time.value
        # sinus vertical
        z = self.amplitude * np.sin(2 * np.pi * t / self.period)
        # Position d’un Rigid3d = [tx, ty, tz, qx, qy, qz, qw]
        # → ici, seule la translation (0,0,z) change
        with self.mo.position.writeableArray() as pos:
            pos[0] = [0.0, 0.0, z, 0.0, 0.0, 0.0, 1.0]
        print(f"time={t:.2f}s, imposed position z={z:.2f}")

def createScene(rootNode):
    scaleForGraph=1000
    #rootNode.addObject("VisualGrid", nbSubdiv=10, size=scaleForGraph)
    # Define the root node properties

    rootNode.dt=0.01 
    # Loading all required SOFA modules
    confignode = rootNode.addChild("Config")
    confignode.addObject('RequiredPlugin', name='Sofa.Component.MechanicalLoad')
    confignode.addObject('RequiredPlugin', name="Sofa.Component.AnimationLoop", printLog=False)
    confignode.addObject('RequiredPlugin', name="Sofa.Component.Collision.Detection.Algorithm", printLog=False)
    confignode.addObject('RequiredPlugin', name="Sofa.Component.Collision.Detection.Intersection", printLog=False)
    confignode.addObject('RequiredPlugin', name="Sofa.Component.Collision.Geometry", printLog=False)
    confignode.addObject('RequiredPlugin', name="Sofa.Component.Collision.Response.Contact", printLog=False)
    confignode.addObject('RequiredPlugin', name="Sofa.Component.Constraint.Lagrangian.Correction", printLog=False)
    confignode.addObject('RequiredPlugin', name="Sofa.Component.Constraint.Lagrangian.Solver", printLog=False)
    confignode.addObject('RequiredPlugin', name="Sofa.Component.IO.Mesh", printLog=False)
    confignode.addObject('RequiredPlugin', name="Sofa.Component.LinearSolver.Iterative", printLog=False)
    confignode.addObject('RequiredPlugin', name="Sofa.Component.Mapping.NonLinear", printLog=False)
    confignode.addObject('RequiredPlugin', name="Sofa.Component.Mass", printLog=False)
    confignode.addObject('RequiredPlugin', name="Sofa.Component.ODESolver.Backward", printLog=False)
    confignode.addObject('RequiredPlugin', name="Sofa.Component.StateContainer", printLog=False)
    confignode.addObject('RequiredPlugin', name="Sofa.Component.Topology.Container.Constant", printLog=False)
    confignode.addObject('RequiredPlugin', name="Sofa.Component.Visual", printLog=False)
    confignode.addObject('RequiredPlugin', name="Sofa.GL.Component.Rendering3D", printLog=False)
    confignode.addObject('OglSceneFrame', style="Arrows", alignment="TopRight")
    confignode.addObject('RequiredPlugin', name="Sofa.Component.MechanicalLoad", printLog=False)
    # Collision pipeline
    rootNode.addObject('DefaultAnimationLoop')
    rootNode.addObject('GenericConstraintSolver', tolerance="1e-6", maxIterations="1000")
    rootNode.addObject('BruteForceBroadPhase')
    rootNode.addObject('BVHNarrowPhase')
    act=False
    move_up=True
    if not act: 
        if move_up:
            movingTooth=False
            movingCandy=True
            movingTongue=True
            rootNode.gravity=[0.0,0.0,9.81]
        if not move_up:
            movingTooth=False
            movingCandy=True
            movingTongue=True
            rootNode.gravity=[0.0,0.0,-9.81]
    if act:
        movingTooth=False
        movingCandy=True
        movingTongue=True
        rootNode.gravity=[0.0,0.0,9.81]
    rootNode.addObject('CollisionResponse', name="response", response="PenalityContactForceField")
    rootNode.addObject('LocalMinDistance', alarmDistance=10, contactDistance=5, angleCone=0.01)
    totalMass = 1.0
    volume = 1.0
    inertiaMatrix=[1., 0., 0., 0., 1., 0., 0., 0., 1.]
    
    tooth = rootNode.addChild("tooth")
    tooth.addObject('EulerImplicitSolver', name='odesolver')
    tooth.addObject('CGLinearSolver', name='Solver', iterations=25, tolerance=1e-05, threshold=1e-05)
    tooth.addObject('MechanicalObject', name="tooth_mo", template="Rigid3d", translation2=[0., 0., 0.], rotation2=[0., 0., 0.], showObjectScale=scaleForGraph)
    #tooth.addObject('UniformMass',totalMass=1)
    
    toothVisu = tooth.addChild("VisualModel")
    toothVisu.loader = toothVisu.addObject('MeshSTLLoader', name="loader", filename="C:/Users/capeltier/Nextcloud/MyDrive/ProjetsEnCours/2023_Digimouth/digimouth_work/sofaTests/mesh/tooth.stl")
    toothVisu.addObject('OglModel', name="model", src="@loader", scale3d=[scaleForGraph,scaleForGraph,scaleForGraph], color=[1., 1., 1.], updateNormals=False)
    toothVisu.addObject('RigidMapping')
    rootNode.addObject('CollisionPipeline')
    tooth_collision = tooth.addChild('tooth_collision')
    tooth_collision.addObject('MeshSTLLoader', name="loader", filename="C:/Users/capeltier/Nextcloud/MyDrive/ProjetsEnCours/2023_Digimouth/digimouth_work/sofaTests//mesh/tooth.stl", triangulate="true", scale=scaleForGraph)
    tooth_collision.addObject('MeshTopology', src="@loader")
    tooth_collision.addObject('MechanicalObject')
    tooth_collision.addObject('TriangleCollisionModel',moving=movingTooth, simulated=movingTooth)
    tooth_collision.addObject('LineCollisionModel',moving=movingTooth, simulated=movingTooth)
    tooth_collision.addObject('PointCollisionModel',moving=movingTooth, simulated=movingTooth)
    tooth_collision.addObject('RigidMapping')

    #### Visualization subnode for the tooth


    # Creating the candy object
    candy = rootNode.addChild("candy")
    candy.addObject('EulerImplicitSolver', name='odesolver')
    candy.addObject('CGLinearSolver', name='Solver', iterations=25, tolerance=1e-05, threshold=1e-05)
    candy.addObject('MechanicalObject', name="mstate", template="Rigid3d", translation2=[0.0,-0.0,0.0], rotation2=[0., 0., 0.], showObjectScale=scaleForGraph)
    candy.addObject('UniformMass',totalMass=1)
    
    #### Collision subnode for the candy

    candyCollis = candy.addChild('collision')
    candyCollis.addObject('MeshSTLLoader', name="loader", filename="C:/Users/capeltier/Nextcloud/MyDrive/ProjetsEnCours/2023_Digimouth/digimouth_work/sofaTests/mesh/bonbon.stl", triangulate="true", scale=scaleForGraph)
    candyCollis.addObject('MeshTopology', src="@loader")
    candyCollis.addObject('MechanicalObject')
    candyCollis.addObject('TriangleCollisionModel', moving=movingCandy, simulated=movingCandy)
    candyCollis.addObject('LineCollisionModel', moving=movingCandy, simulated=movingCandy)
    candyCollis.addObject('PointCollisionModel', moving=movingCandy, simulated=movingCandy)
    candyCollis.addObject('RigidMapping')

    # #### Visualization subnode for the candy
    candyVisu = candy.addChild("VisualModel")
    candyVisu.loader = candyVisu.addObject('MeshSTLLoader', name="loader", filename="C:/Users/capeltier/Nextcloud/MyDrive/ProjetsEnCours/2023_Digimouth/digimouth_work/sofaTests/mesh/bonbon.stl")
    candyVisu.addObject('OglModel', name="model", src="@loader", scale3d=[scaleForGraph, scaleForGraph,scaleForGraph]*1, color=[0.9, 1., 0.,0.7], updateNormals=False)
    candyVisu.addObject('RigidMapping')

    # Adding tongue node (visualization only)
    tongue = rootNode.addChild("tongue")
    tongue.addObject('EulerImplicitSolver', name='odesolver')
    tongue.addObject('CGLinearSolver', name='Solver', iterations=25, tolerance=1e-05, threshold=1e-05)
    tongue.addObject('MechanicalObject', name="tongue_mo", template="Rigid3d", translation2=[0.0,-0.0,0.0], rotation2=[0., 0., 0.], showObjectScale=scaleForGraph)
    tongue.addObject('UniformMass', name="mass", vertexMass=[totalMass, volume, inertiaMatrix[:]])
    if act:
        tongue.addObject(MoveTongueController(name="MoveToothController"  , MechanicalObject=tongue.tongue_mo) ) 
  
    # #### Visualization subnode for the candy
    tongueVisu = tongue.addChild("VisualModel")
    tongueVisu.loader = tongueVisu.addObject('MeshSTLLoader', name="loader", filename="C:/Users/capeltier/Nextcloud/MyDrive/ProjetsEnCours/2023_Digimouth/digimouth_work/sofaTests/mesh/tongue.stl")
    tongueVisu.addObject('OglModel', name="model", src="@loader", scale3d=[scaleForGraph, scaleForGraph,scaleForGraph]*1, color=[0.9, 0.2, 0.2], updateNormals=False)
    tongueVisu.addObject('RigidMapping') 
    
    
    collision_tongue = tongue.addChild('collision_tongue')
    collision_tongue.addObject('MeshSTLLoader', name="loader", filename="C:/Users/capeltier/Nextcloud/MyDrive/ProjetsEnCours/2023_Digimouth/digimouth_work/sofaTests//mesh/tongue.stl", triangulate="true", scale=scaleForGraph)
    collision_tongue.addObject('MeshTopology', src="@loader")
    collision_tongue.addObject('MechanicalObject', src="@loader")
    collision_tongue.addObject('TriangleCollisionModel', moving=movingTongue, simulated=movingTongue)
    collision_tongue.addObject('LineCollisionModel', moving=movingTongue, simulated=movingTongue)
    collision_tongue.addObject('PointCollisionModel', moving=movingTongue, simulated=movingTongue)
    collision_tongue.addObject('RigidMapping')
    return rootNode


# Function used only if this script is called from a python environment
import os
if __name__ == '__main__':
    main()
    mesh_dir = os.path.join(os.path.dirname(__file__), "mesh")
    print("Chemin fichier :", mesh_dir)```

[hugtalbot]

Hi @CaroPeltier

As you know, using the DefaultAnimationLoop the only collision response that will work is the penality-based response. It would be a point of attention for later, since penalities are known to be hard to tune and thus possibly unstable.

In your simulation, when you activate the DisplayFlag "Show Detection Outputs" do you see any contact detected ?

• If yes, make sure that your alarm and contact distance is appropriately set
• If no, possibly change the intersection used in the narrow phase (here LocalMinDistance) with another one, like the MinProximityIntersection

Hope this helps

[github-actions[bot]]

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@CaroPeltier
Feedback has been given to you by the project reviewers, however we have not received a response from you. Without further news in the coming weeks, this discussion will be automatically closed in order to keep this forum clean and fresh 🌱 Thank you for your understanding