#447 Plate mode NURBS ray tracing

[Bojian Wu]

Hi, brlcad,

Recently, I have been working on the plate mode NURBS raytracing, and here is my patch about my implementation. The main goal is to keep a consistent ray tracing behaviours occured in both BoT and B-rep, because all the implementation in BoT is an excellent example to follow.

The basic idea here is just to seperate one hit into two hit points including a pair of in and out one no matter it is in surface mode or plate mode if the mesh is open(For closed mesh, I do not touch anything at present but keeping its old implementation.). In surface mode, the in and out should be the same one but with opposite normal direction. But in plate mode, things are different, we need to offset the in/out hit distance according to the thickness value assigned to the mesh. Currently, I center the real hit point and move the in hit point along the reverse incident shooting ray direction with half the thickness value and vice verse for the out one.

Here, I put all my code together including my previous work and submit a patch, please check it and let me know if I make any mistakes. Thanks very much. :-)

Best,
Bojian