The question is, why do this?<p>Is it for fun? If so, great. Not my cup of tea personally, but I can imagine how it could be someone's.<p>If not for fun, what is the point? It presumably isn't to create a usable ray-tracing system. Perhaps a challenge to improve the author's Excel skills? If so, I suggest they move on to a proper programming language and visualisation system.<p>There seems to be this obsession, among some people, with using Excel for all sorts of inappropriate things, and I have a sinking feeling that this might be related to that. A system for generating contracts using Excel formulas, in Excel, instead of using mail merge, or something else, with Word or something else designed to format prose text, is a horrible example I have come across at work.