BlitzODE Physics Thread

Trimesh/Trimesh collisions, perform quite well, but there are three minor caveats:


The stepsize you use will, in general, have to be reduced for accurate collision resolution. Non-convex shape collision is much more dependent on the collision geometry than primitive collisions. Further, the local contact geometry will change more rapidly (and in a more complex fashion) for non-convex polytopes than it does for simple, convex polytopes such as spheres and cubes.

In order to efficiently resolve collisions, dCollideTTL needs the positions of the colliding trimeshes in the previous timestep. This is used to calculate an estimated velocity of each colliding triangle, which is used to find the direction of impact, contact normals, etc. This requires the user to update these variables at every timestep. This update is performed outside of ODE, so it is not included in ODE itself. The code to do this looks something like this:

  const double *DoubleArrayPtr =
    Bodies[BodyIndex].TransformationMatrix->GetArray();
  dGeomTriMeshDataSet( TriMeshData,
    TRIMESH_LAST_TRANSFORMATION,
    (void *) DoubleArrayPtr );

The transformation matrix is the standard 4x4 homogeneous transform matrix, and the "DoubleArray" is the standard flattened array of the 16 matrix values.