I wrote this back in late 2004 or so, when I was doing a bunch of spreadsheet work. It's a simple (fixed scene) ray tracer, with those most traditional of items, a mirrored sphere and a checkerboard plane.
It's written purely in function mode, with no Visual Basic involved, so that the scene is created by fill down and fill right of the ray-tracing formulae, spread over a number of tabs. Part of that means, of course, that there's no recursion, hence it being rather specialised for this particular scene.
The display is generated using conditional formatting on the values in the cells. Since the number of conditional formats is small, extra gradation is produced using a form of dithering.
While dropping big lumps of binary into GitHub is probably not really the way to go, especially ones representing ancient projects, this is My First GitHub Repo, so I thought I'd start with something I had lying around!
Simon Frankau