I'm building a dynamic scene containing subdivision geometry with continuously updating vertex buffers. I'm making rtcIntersect calls in that scene and the intersections points are updating correctly.
Also, for each intersection I'm calling rtcInterpolate on the vertex buffer and using the calculated tangents to construct an interpolated normal. That works correctly on the first frame, but if the vertex buffer is changed the tangents are no longer correct. Deleting and rebuilding the geometry rather than updating the vertex buffer fixes the problem.
I'm guessing that your suggested solution might be to use OpenSubdiv rather than the built in subdivision geometry. I am planning to make that change anyway so if that will also solve this problem I should be OK going forward, but I thought I would ask in case I might be doing something else wrong.