Nonlinear Ray Tracing for Displacement and Shell Mapping
Shinji Ogaki · 2023
Displacement mapping and shell mapping add fine-scale geometric features to meshes and can significantly enhance the realism of an object’s surface representation. Both methods generate geometry within a layer between the base mesh and its offset mesh called a shell. It is not easy to simultaneously achieve high ray tracing performance, low memory consumption, interactive feedback, and ease of implementation, partly because the mapping between shell and texture space is nonlinear. This paper introduces a new efficient approach to perform acceleration structure traversal and intersection tests against microtriangles entirely in texture space by formulating nonlinear rays as degree-2 rational functions. Our method simplifies the implementation of tessellation-free displacement mapping and smooth shell mapping and works even if base mesh triangles are degenerated in uv space.