I used to use an open source ray tracer called POV-Ray in the early nineties and it was pretty impressive. Here’s an example of an early scene you could render with it: https://amp.reddit.com/r/vintagecgi/comments/eswamt/chesspov...

I did a few similar scenes using a software renderer I wrote - not a ray tracer, though - for a Computer Graphics class in the early 2000s. Except I used a painting by Jim Todd as background, named "What Price Victory":

http://1.bp.blogspot.com/_fmfAOCgGNJU/SQuCxkXJiRI/AAAAAAAAGE...

Less active the last several years, but it's still around:

http://www.povray.org/

https://github.com/POV-Ray/povray

I remember using povray too. Officially it required a 386 pc but it could be recompiled for 286, which is what I did. My PC had a IIT 2c87 coprocessor that had special 4x4 matrix multiply instructions, so of course I modified povray to take advantage of that.

That matmul instruction seemed oddly specific, so I had to google that, and lo and behold, indeed there was such a thing! [0]

Do you remember what kind of speed ups that thing gave you? I wonder if you could play to backport some modern AI algorithms to it and run them at reasonable speeds -- however being a 286 I imagine it'd be quite a challenge.

[0] https://books.google.com/books?id=RD0EAAAAMBAJ&pg=PA89&lpg=P...

I no longer remember the numbers but the speed ups were measurable. That FPU had 24 FP registers (as compared to 8 in a regular 287). The best case would be to load a matrix to the registers and then have a bunch of vectors to multiply the stored matrix with. Then this thing could fly. Loading the matrix to the registers was slow though because 287 coprocessors used DMA to communicate with memory.

Well, the algorithm was developed in the 1600's, but I remember Turner Whitted's 1979 SIGGRAPH paper blowing me away. I mean, sure, they were slow, but before REYES, they were about the only solution to GlobIlum. (Forward from the lights and backwards from the camera - you could even do specular lighting!)

Reyes isn't a global illumination algorithm, in fact it doesn't prescribe any kind of illumination at all. Global illumination was first described by Cindy Goral, Ken Torrance and Donald Greenberg in the constrained setting of diffuse reflectance in polygonal scenes; the first general GI algorithm, path tracing, was introduced in 1986 by James Kajiya.

https://en.wikipedia.org/wiki/Radiosity_(computer_graphics)

The way I implement REYES, it does. But no doubt- Kajiya was the man.

I'm curious how you would solve the GI problem with Reyes; note that doing something like like photon mapping or radiosity isn't Reyes itself.

Photon mapping. I've never gotten radiosity debugged properly. I tend to like Reyes as something that works for NURB tersellation for me than the triangle interpolation thing. It could be that I'm a lazy programmer that has trouble with textures using classic z-buff techniques.