Plate Mode NURBS raytracing

Often when modeling, it is necessary to represent solids with very large surface areas but very small thicknesses, such as sheet metal. It is often impractical to represent these thin solids exactly as bounded volumes, so an alternative approach is to model a surface and "tag" it with an implicit thickness. That is, when a ray intersects the surface, an "out" hit point is assigned some small distance from the initial hit point along the ray. BRL-CAD currently implements this modeling technique for the BoT primitive, and BoTs that utilize it are referred to as "plate mode".

This task would be to implement plate mode raytracing for NURBS surfaces. Thin materials (such as those used for airplane skins) are a common modeling scenario for NURBS models.

A student proposal on this topic would need demonstrate research into the various issues that arise when plate-mode raytracing is used and how to address them.


  • src/librt/primitives/brep/brep.cpp
    • our new nurbs primitive
  • src/librt/primitives/bot
    • our "bag o' triangles" primitive implements plate mode meshes, perfect example to follow


  • Familiarity with C/C++