btTriangleMeshShape to btTriangleShape (InternalEdges prob)

[Karrok]

Is it possible to make a btTriangleShape out of a btTriangleMeshShape?

I have a btBvhTriangleMeshShape that is recognised as a TRIANGLE_MESH_SHAPE_PROXYTYPE.
However for the InternalEdgeUtility I require a btTriangleShape (TRIANGLE_SHAPE_PROXYTYPE).

The model is a 3d non-convex object loaded from .osg and created as a btBvhTriangleMesh using osgBullet.
The btTriMeshCollisionShapeFromOSG returns a btTriangleMeshShape (while using btBvhTriangleMeshShape inside the function).

It gathers all the vertices and then adds these as triangles to a btTriangleMesh (which is added to the btBvhTriangleMeshShape.

Now I asume I could use a similar visitor to get all the vertices, but how do I construct a valid 3D TriangleShape from these vertices?

Cheers

edit:
the OSG model is generated from parametric surfaces (with a thickness added) which represent the world, these models have also been given a thickness (so it becomes a triangle mesh from that surface+thickness).

This means that there are a good number of internal edges, which mess up my cylinder-wheeled vehicles.
And the internal edge util only accepts TRIANGLE_SHAPE_PROXYTYPE, not meshes.

[Karrok]

Or in other words:

How do I fix the internal edge problem if I only have a btBvhTriangleMeshShape (which is concave).

[zarlox]

Or in other words:

How do I fix the internal edge problem if I only have a btBvhTriangleMeshShape (which is concave).

Well, as a matter of fact, btBvhTriangleMeshShape is the shape that you need to pass to the internal edge utility function. So i do not understand why you think you can't. Look at this post:

http://bulletphysics.org/Bullet/phpBB3/ ... 566#p24566

[Karrok]

I realise that, but the shape returned from getShapeType() is not TRIANGLE_SHAPE_PROXYTYPE as it was generated from osgBullet, which turns an osg file into a TriangleMesh.

And I am not sure how I should alter the shape creation to make a proper btBvhTriangleMeshShape that would return a TRIANGLE_SHAPE_PROXYTYPE. I can use osgBullets visitor to gather all vertices from the osg node. But I don't know how to construct a compatible btBvhTriangleMeshShape.

[zarlox]

Sorry i misunderstood the question. I'm affraid i do not know much on that side either

[mi076]

the function is not from Bullet... try write own, but returning btBvhTriangleMeshShape *,
the original is -

Code: Select all

btTriangleMeshShape* btTriMeshCollisionShapeFromOSG( osg::Node* node )
{
    ComputeTriMeshVisitor visitor;
    node->accept( visitor );

    osg::Vec3Array* vertices = visitor.getTriMesh();
    if( vertices->size() < 3 )
    {
        osg::notify( osg::WARN ) << "osgbCollision::btTriMeshCollisionShapeFromOSG, no triangles found" << std::endl;
        return( NULL );
    }

    btTriangleMesh* mesh = new btTriangleMesh;
    for( size_t i = 0; i + 2 < vertices->size(); i += 3 )
    {
        osg::Vec3& p1 = ( *vertices )[ i ];
        osg::Vec3& p2 = ( *vertices )[ i + 1 ];
        osg::Vec3& p3 = ( *vertices )[ i + 2 ];
        mesh->addTriangle( osgbCollision::asBtVector3( p1 ),
            osgbCollision::asBtVector3( p2 ), osgbCollision::asBtVector3( p3 ) );
    }

    btBvhTriangleMeshShape* meshShape = new btBvhTriangleMeshShape( mesh, true );
    return( meshShape );
}

[Karrok]

where the

Code: Select all

btTriangleMesh* mesh = new btTriangleMesh;

causes the btBvhTriangleMesh to identify as a Triangle mesh shape instead of a triangle shape as is expected by the internal edge utility.

So the question remains, how can I create a valid triangle shape?

And I have tried with just changing the return types, which does not work with the TriangleMesh created internally.

[mi076]

AFAIK, Bvh shape is always TRIANGLE_MESH_SHAPE_PROXYTYPE ... but may be i don't understand the questions... anyway, you can also set up mesh interface like that

Code: Select all

btTriangleIndexVertexArray * mesh_interface = new btTriangleIndexVertexArray(
                                                        faces_size/12,
                                                        index_array,
                                                        3*sizeof(int),
                                                        j+1,
                                                        (btScalar *) &vertex_array[0][0],
                                                        sizeof(btVector3));
btBvhTriangleMeshShape * shape = new btBvhTriangleMeshShape(mesh_interface,true,true);

[Karrok]

So how do I go from having a bunch of vertices to actually getting all parameters?

There seems to be another problem with using btBvHTriangleMeshShapes though:
in the bvhTriangleMeshShape header we see:
btBvhTriangleMeshShape() : btTriangleMeshShape(0),m_bvh(0),m_ownsBvh(false) {m_shapeType = TRIANGLE_MESH_SHAPE_PROXYTYPE;};

and in the internal edge util in btAdjustInternalEdgeContacts:
if (colObj0->getCollisionShape()->getShapeType() != TRIANGLE_SHAPE_PROXYTYPE)
return;

So logically no btbvhtriangle mesh can get it's edges fixed right ?

however in the demo (I checked) even though the shapes are created as TRIANGLE_MESH_SHAPE_PROXYTYPE, once they reach the callback, they magically appear as being TRIANGLE_SHAPE_PROXYTYPE, and nowhere in the code can I find what makes this happen.

[mi076]

however in the demo (I checked) even though the shapes are created as TRIANGLE_MESH_SHAPE_PROXYTYPE, once they reach the callback, they magically appear as being TRIANGLE_SHAPE_PROXYTYPE, and nowhere in the code can I find what makes this happen.

afaik, at the end the callback gets individual triangles, so probably it is not a mistake... not 100% sure, didn't use this code.... anyway may be the idea to use "btTriangleIndexVertexArray * mesh_interface" was not wrong because i have seen
"meshInterface->getLockedReadOnlyVertexIndexBase(...)" somewhere in void btGenerateInternalEdgeInfo (btBvhTriangleMeshShape*trimeshShape, btTriangleInfoMap* triangleInfoMap)....

[Karrok]

Seemed to have fixed it and it's now getting through the callback.

Problem was a wrongly placed callback.
thanks for the help!