Already got PRBT a while back, just haven’t read through it yet.
Build your own Raytracer, very cool 
and the man in the picture looks like me now 
been awake for 25 hour strait… “I feel your pain” and stil got 4 hours of work 
thats the part where u start seen wird stuff u never thinked about before ( great thing to come up with modeling idears, if your body can handle it LOL )