ray tracing survey

ray tracing vs casting :
http://permadi.com/1996/05/ray-casting-tutorial-table-of-contents/

ray tracing :
https://www.cs.unc.edu/~rademach/xroads-RT/RTarticle.html

c++ example :
http://www.cosinekitty.com/raytrace/chapter05_cpp_code.html

ray tacing, ray packet, SAH(Surface Area Heuristic) :
http://www.cs.cmu.edu/afs/cs/academic/class/15869-f11/www/lectures/14_raytracing.pdf

아직 조사중.