Grow shadow regions slightly to avoid linear filtering artifacts

If you get the sun and camera angles just right, the overlap between neighboring shadowmap regions can disappear, resulting in a slight gap where the linear filtering at the edge of the shadowmap is clear/white/unshadowed. To fix this, the calculated world region associated with a given shadowmap should be expanded by some small amount like 1% or 5% before shadowmaps are rendered. There might be other solutions, but requiring a small amount of overlap is necessary for shadowmap blending anyway, and a lot of game engines support shadowmap blending.

Example of problem:

Exaggerated:

Original example with overlay: