Low-level test for a box and trimesh collision

[venzon]

I'd like to use some of bullet's lower level collision detection functions to collide a box shape (btBoxShape) with a trimesh shape (btBvhTriangleMeshShape). In the demo called "CollisionDemo", a box-to-box collision is done, but the functions/classes used seem specific to convex-convex collision. What should I use to do the convex-concave (box-trimesh) collision test?

Alternately, by looking in the btCollisionWorld::performDiscreteCollisionDetection implementation, I thought I might be able to create my own btOverlappingPairCache that just has the box and trimesh I'm interested in, and then do something like:

Code: Select all

my_bt_collision_world->getDispatcher()->dispatchAllCollisionPairs(my_pair_cache,getDispatchInfo());

This would allow me to use my already existing handler logic for looking at the collision manifolds.

Do either of these ideas sound like the Right Way to do this?

[venzon]

I ended up going the latter route and it works fine. The only wrinkle is that I had to manually remove (release) all of the manifolds once I was done with them.

[Erwin Coumans]

What should I use to do the convex-concave (box-trimesh) collision test?

You need to use the btConvexConcaveCollisionAlgorithm::processCollision.

One low level way of doing this (given collision objects for boxshape and trimesh shape):
Use the dispatcher to find/create the collision algorithm (btConvexConcaveCollisionAlgorithm) and call algorithm->processCollision. See void btCollisionDispatcher::defaultNearCallback for details.

Thanks,
Erwin