What do you mean? That loop determines for a shoft shadow how "deep" it should be by accessing the un-smoothed ray at the position which corresponds to the middle point of the fade. Apparantly it hit the end of the ray list for some reason, which should really only happen if the mid point somehow was outside the ray list range (after all, I have 4 lists covering 90° each). On paper, this positively shouldn't happen, as all points are products of projections of existing points and suitable points close to the light point. Indeed it generally is pretty conservative with projecting points "inwards" when in doubt - which is one part of the explanation for the black triangles at 45°.

One point falling out of the section is actually semi-reproducable in tutorial 1 - sometimes when you walk into the tunnel, you see a bright triangle right-top in the earth. It doesn't cause a crash, but it's probably the same root cause. I'll just have to bite the bullet sometime and go through step-by-step logs of everything until I can pin down at what point exactly that point goes astray.

Could mean that you are an interesting case for Peter ;)

Clonkonaut's shader seems to be from the default branch (doesn't mention lightTex), so no wonder it doesn't change anything. Does the log have anything more to say before that generic error message? What sort of GPU do you have?

That's one of the options I'm exploring. Makes everything explode even worse though :/

And yes, they are updated every frame. However, I'm currently "smoothing" it by alpha-blitting the old light map over it every frame. That makes it look better, as it covers up some jitter due to everything being pixels at some point - when you stand directly in front of something, even small bumps in the ground the Clonk is walking over might cause significant changes in shadows.

So this kind of effect might be less visible.