[jfries]

If you have a guarantee for the worst case of generating a pixel (which you indicate by saying that you never drop frames), couldn't you get rid of the framebuffer? Schedule pixel generation so that they complete just in time for when they're needed for output.

This would save up RAM for other things (and be a fun exercice to get right).

[nickmqb]

That's a good observation! This technique is also known as "racing the beam". The problem is a mismatch of refresh rates; the VGA display operates at 60 Hz but the ray tracer is not capable of producing that many pixels, it can only do 30 fps. So we need a frame buffer to store the result.