Plate Mode NURBS raytracing

In Constructive Solid Geometry (CSG) system, the modeling process is usually represented as boolean operations of some basic primitives such as cubes, spheres, etc. This method is often used in solid modeling system and its operations always construct the basic solid modeling pipeline. Besides, the boundary representation (B-rep) is also a method for representing models by using a collection a connected surface elements. So for the purpose of solid modeling, it is commonly impractical to represent these thin solids exactly as bounded volume, thus an available approach is to assign an implicit thickness to each face and then we can consider the thickness as a face property. Simply speaking, when shooting a ray towards the B-rep model, we can get ‘in’ and ‘out’ hit point from a face while the ‘out’ hit point is a small offset from the ‘in’ one with given thickness value along the ray direction.