This repository contains the source code of .S.k.y. demo effect by gynvael.coldwind//vx. If you want to know more about the algorithm, read the article.
The demo was ported by me (i.e. vamastah) for Bittboy and compatibles.
Well, you just need to run the demo and watch. The first launch takes a long time (~1 minute), because a normal map needs to be precalculated.
You can use a directional pad to move the light manually. Press START to see a FPS (frames per second) counter.