Question about the ChParticleCloud, Crash when collisions are enabled

[Zaftrox]

Hi, i wanted to create a particlecloud to handle a bunch of cylindrical objects in pychrono. However, when i setup the particlecloud then enable the collisions, it crashs immediately.

Here's the snippet :

# Particles cloud :
particles = chrono.ChParticleCloud()
particles.SetMass(simMat["ParticleMass"])
particles.SetInertiaXX(chrono.ChVector3d( simMat["ParticleInertia"],  simMat["ParticleInertia"],  simMat["ParticleInertia"]))

# Collision shape/model :
colModel = chrono.ChCollisionModel()
colModel.Clear()
cylShape = chrono.ChCollisionShapeCylinder(material, .01, .002)
colModel.AddShape(cylShape)
particles.AddCollisionModel(colModel)
particles.AddCollisionShape(cylShape)

visShape = chrono.ChVisualShapeCylinder(.01, .002)
frame = chrono.ChFramed(chrono.ChVector3d(0,0,0), chrono.QuatFromAngleAxis(chrono.CH_PI/2, chrono.ChVector3d(1,0,0)))
particles.AddVisualShape(visShape, frame)

# addition loop :
for i in range(20):
    possys = chrono.ChCoordsysd(
        chrono.ChVector3d(random.uniform(-.3, .3), random.uniform(-.3, .3), 0),
        chrono.QuatFromAngleAxis(-chrono.CH_PI/2, chrono.ChVector3d(1,0,0))
    )
    particles.AddParticle(possys)
#particles.EnableCollision(True)
system.Add(particles)

[Dan Negrut]

Hi, would you mind dropping the entire PyChrono script, top to bottom, that demonstrates the problem?

 

NOTE: this is a public forum, remove any sensitive information/data.

 

Thank you,

Dan

---------------------------------------------

Bernard A. and Frances M. Weideman Professor

NVIDIA CUDA Fellow

Department of Mechanical Engineering

Department of Computer Science

University of Wisconsin - Madison

4150ME, 1513 University Avenue

Madison, WI 53706-1572

608 772 0914

http://sbel.wisc.edu/

http://projectchrono.org/

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[Zaftrox]

here's the code :

import pychrono.core as chrono
import pychrono.irrlicht as chronoirr
import random
import numpy as np

# Sim-DATA :
simData = {
    "Density" : 5200,
    "ExpectedDiameter" : .05e-3
}
simData["ParticleVolume"] = (3/4)*np.pi*np.power((simData["ExpectedDiameter"]/2), 3)
simData["ParticleMass"] = simData["ParticleVolume"]*simData["Density"]
simData["ParticleInertia"] = (2/5)*simData["ParticleMass"]*np.power((simData["ExpectedDiameter"]/2), 2)

# Create Chrono physical system
system = chrono.ChSystemNSC()
system.SetCollisionSystemType(chrono.ChCollisionSystem.Type_MULTICORE)
system.SetGravitationalAcceleration(chrono.ChVector3d(0, -9.81, 0))
ground = chrono.ChBody()
ground.SetFixed(True)
system.Add(ground)
material = chrono.ChContactMaterialNSC()
material.SetFriction(.5)

def constrain_to_2D(body):
    # Dummy body as reference :
    dummy = chrono.ChBodyAuxRef()
    dummy.SetFixed(True)
    system.AddBody(dummy)

    # Planar constraint and its frame :
    plane_constraint = chrono.ChLinkLockPlanar()
    frame_abs = chrono.ChFramed(body.GetPos(), chrono.QUNIT)
    # Init :
    plane_constraint.Initialize(body, dummy, True, frame_abs, frame_abs)
    # constraint generic mate :
    lock = chrono.ChLinkMateGeneric()
    lock.Initialize(body, dummy, False, frame_abs, frame_abs)
    # Constrain Tz and X/Y rotation in case of offset :
    lock.SetConstrainedCoords(False, False, True,  # Tx, Ty, Tz
                              True, True, False)   # Rx, Ry, Rz

    system.Add(lock)
    system.AddLink(plane_constraint)

def importMeshBody(meshFile, material, contrained2D=False, fixed=True, scale=0.001, initialPos=chrono.ChVector3d(0, 0, 0), colorVec=chrono.ChColor(0.3, 0.3, 0.3)):
    # Prior :
    body = chrono.ChBody()
    system.Add(body)
    body.SetPos(initialPos)
    if contrained2D :
        constrain_to_2D(body)
    # mesh :
    mesh = chrono.ChTriangleMeshConnected()
    mesh.LoadWavefrontMesh(meshFile)
    transformationMatrix = chrono.ChMatrix33d(scale)
    mesh.Transform(chrono.ChVector3d(0,0,0), transformationMatrix)

    # Visualization part :
    visShape = chrono.ChVisualShapeTriangleMesh()
    visShape.SetMesh(mesh)
    visShape.SetColor(colorVec)
    body.AddVisualShape(visShape)

    # Collision part :
    body_ct_shape = chrono.ChCollisionShapeTriangleMesh(material, mesh, False, False, 0.01)
    body.AddCollisionShape(body_ct_shape)
    body.EnableCollision(True)
    body.SetFixed(fixed)
    return body

plate = importMeshBody("test PLATE.obj", material, contrained2D=True, scale=.001, fixed=True)

# Particles cloud :
particles = chrono.ChParticleCloud()

particles.SetMass(simData["ParticleMass"])
particles.SetInertiaXX(chrono.ChVector3d(simData["ParticleInertia"], simData["ParticleInertia"], simData["ParticleInertia"]))

# Collision shape/model :
colModel = chrono.ChCollisionModel()
colModel.Clear()

cylShape = chrono.ChCollisionShapeCylinder(material, .01, .002)   # radius

colModel.AddShape(cylShape)
particles.AddCollisionModel(colModel)
particles.AddCollisionShape(cylShape)

visShape = chrono.ChVisualShapeCylinder(.01, .002)
frame = chrono.ChFramed(chrono.ChVector3d(0,0,0), chrono.QuatFromAngleAxis(chrono.CH_PI/2, chrono.ChVector3d(1,0,0)))
particles.AddVisualShape(visShape, frame)

# Add particles (positions only)

for i in range(20):
    possys = chrono.ChCoordsysd(
        chrono.ChVector3d(random.uniform(-.3, .3), random.uniform(-.3, .3), 0),
        chrono.QuatFromAngleAxis(-chrono.CH_PI/2, chrono.ChVector3d(1,0,0))
    )
    particles.AddParticle(possys)

particles.EnableCollision(True)
system.Add(particles)

vis = chronoirr.ChVisualSystemIrrlicht()
vis.AttachSystem(system)
vis.SetWindowSize(1024, 768)
vis.SetWindowTitle("Mixer simulator")
vis.Initialize()
vis.AddSkyBox()
vis.AddCamera(chrono.ChVector3d(0, 0, 2))
vis.AddTypicalLights()
   
time_step = 0.005
while vis.Run():
    vis.BeginScene()
    vis.Render()
    vis.EndScene()
    system.DoStepDynamics(time_step)

[Bocheng Zou]

Hi Zaftrox,

Thank you for raising the issue. To help us investigate, could you please report if there's any output in the terminal before the program crashes?

Best,

Bocheng Zou

To view this discussion visit https://groups.google.com/d/msgid/projectchrono/0c2e271d-964f-444b-81e5-ceddcb392a48n%40googlegroups.com.

[Zaftrox]

No, there's nothing.

When the simulation starts and the rendering window pop-up it freezes instantaneously and crash. It comes from the collision so if the particles cloud is set fixed or by disabling the collision, the simulation works fine.

[Bocheng Zou]

Hi Zaftrox,

Thank you for the follow up. To help us better identify the problem, could you please upload the "test PLATE.obj" file? In addition, could you please provide information on how do you install the PyChrono. Specifically, if you install PyChrono via conda, could you please also attach your "conda list" output?

Best,

Bocheng Zou

To view this discussion visit https://groups.google.com/d/msgid/projectchrono/40557cce-5ebb-4474-a3da-a6dae265872an%40googlegroups.com.

[Zaftrox]

just installed pychrono 9.0.0 using conda.

btw, i tested without triangularmesh (the test PLATE) and the problem persist.

[Bocheng Zou]

Hi Zaftrox,

Thank you for getting back. The issue has been successfully reproduced on my end. I will look into that and let you know once a fix has been implemented. 

Best,

Bocheng Zou

To view this discussion visit https://groups.google.com/d/msgid/projectchrono/7effc9f8-88fd-4680-b0d1-271ab4b31ee3n%40googlegroups.com.