Cascaded shadow maps

[x2048]

Work in progress here: https://github.com/x2048/minetest/tree/shadow_csm.

Why / goals:

• No distortion => simpler math => easier to maintain
• Better shadow quality or fewer resources for the same quality
• No fading of the shadow at a distance of in the corners of the screen
• Correct shadows for large sparse meshes (Little Lady, clouds etc.)

What works so far:

• Non-colored shadows
• 3 cascades
• update cascade 0 every frame, incremental updates for the other cascades
• soft shadows

Worth it?

[DELTA_FORCE]

I would like to test but I do believe it's worth it. Anything more maintainable is a huge win in my book.

[Astrobe]

If the clouds you mention are the normal MT clouds, yes, do want - especially if it doesn't take too much resources. Cloud shadows could free me from adapting luminosity to cloud coverage, which is a bit tricky because it must work with the sun and the moon.