This is going to sound stupid, but one of the things I had always wanted to write as a kid/teen was a perspective-correct texture mapper. I'd written a few affine mappers before (good enough for some!), but had never really sat down to think about the math since the point in life where I had actually learned enough to work it out. So one idle afternoon in 2011, I spent a couple hours writing a truly bare-bones mapper. I spent zero time on corner cases; these show up as red pixels in the video.