RAPID -- Improvements of v 1.03 over v 1.01

• Robust Tree Building: The first is that the tree building algorithm now consistently constructs a sufficiently deep OBB hierarchy so that all leaf nodes contain exactly one triangle each. The older version sometimes failed an internal consistency check, emitting an error message several times during tree construction, and resulting in a tree which permitted correct collision detection, but with reduced performance.
• Robust Triangle Overlap Test: The second improvement is a new triangle overlap test which is more expensive but much more robust. The old test, based on edge-face intersection tests using gaussian elimination, would sometimes fail when an edge of one triangle was parallel to the face of the other triangle. The new test is based on separating axes, like the OBB overlap test - but is more expensive than an OBB overlap test because triangles don't have the nice structure that the boxes do (see the OBB paper for details).