Rotate a btConvexHullShape via btCompoundShape problem.

2019-04-04T16:13:59+00:00

Hello,

Normally, I build a btConvexHullShape from an HACD generated model like this:

Code:

     //...Retrieve a geometry list from OpenSceneGraph....   .....   .....   for(unsigned int i = 0; i < l_GeometryList.size(); i++) {    osg::Vec3Array* l_GfxVertices = dynamic_cast(l_GeometryList[i]->getVertexArray());    if(!l_GfxVertices) {      continue;    }    btAlignedObjectArray l_PhyVertices;    //Calc centroid    btVector3 l_Centroid = btVector3(0,0,0);    for(unsigned int i = 0; i < l_GfxVertices->size(); i++) {      btVector3 l_Vertex((*l_GfxVertices)[i].x(), (*l_GfxVertices)[i].y(), (*l_GfxVertices)[i].z());      l_Centroid += l_Vertex;    }    l_Centroid *= 1.f/(double(l_GfxVertices->size()));    //Shift vertices around centroid    for(unsigned int i = 0; i < l_GfxVertices->size(); i++) {      btVector3 l_Vertex((*l_GfxVertices)[i].x(), (*l_GfxVertices)[i].y(), (*l_GfxVertices)[i].z());      l_Vertex -= l_Centroid;      l_PhyVertices.push_back(l_Vertex);    }    //Create the convex hull shape    btConvexHullShape* l_ConvexHullShape = new btConvexHullShape(&(l_PhyVertices[0].getX()), l_PhyVertices.size());    l_ConvexHullShape->setMargin(0.001f);    btTransform l_PhyTransform;    l_PhyTransform.setIdentity();    l_PhyTransform.setOrigin(l_Centroid);        btCompoundShape* l_PhyCompoundShape = new btCompoundShape();    l_PhyCompoundShape->addChildShape(l_PhyTransform, l_ConvexHullShape);    }

This code basically works and place the convex hull in the correct position.

Now I need a rotation, so I have simple added the rotation to the l_PhyTransform (for example, after the l_PhyTransform.setOrigin(l_Centroid) line):

Code:

      PhyQuaternion l_quat;      l_quat.setEulerZYX(0, 0, M_PI_2);      l_PhyTransform.setRotation(l_quat);

This code doesn't works as expected (for me): a simple convex shape rotation of 90° (on X). Instead, the rotation there is, but I can see a sort of "degenerated" mesh: some polygons are corrects, some others are like "deformed" and moved in weird position.

Can you tell me where is my silly error?

Many thanks!

Bye

Statistics: Posted by Dox — Thu Apr 04, 2019 4:13 pm

Real-Time Physics Simulation Forum

Rotate a btConvexHullShape via btCompoundShape problem.