Especially raytracing! What I used to do when teaching was taking a few weeks to develop the rasterizer, and then say "OK, 4 weeks to go, time to present your f

Especially raytracing! What I used to do when teaching was taking a few weeks to develop the rasterizer, and then say "OK, 4 weeks to go, time to present your final project - you're making this <image of a raytraced scene with reflections and shadows>, which I'm going to explain within the next 2 hours". Some groups genuinely thought I was joking. But then every one of them managed to write a raytracer, their minds were blown, and they used their renders as desktop backgrounds. I loved that :)