Directional 2 Split Shadow stabilization fix

[mrjustaguy]

Fixes #59232

Before:

2023-10-07.18-01-10.mp4

After:

2023-10-07.17-59-45.mp4

[Calinou]

Tested locally (rebased on top of master 6916349), it works as expected. Shadows are now perfectly stable in motion with all rendering methods (Forward+, Mobile, Compatibility).

4-split PSSM and Orthogonal shadow modes still render correctly.

Note that this doesn't fix #54849.

master

Orthogonal	PSSM 2 Splits1	PSSM 4 Splits

This PR

There are very small differences in still scenes when using PSSM 2 Splits, which is expected.

Orthogonal	PSSM 2 Splits1	PSSM 4 Splits

Footnotes

1. Split distance increased to 0.2 (instead of 0.1) to improve quality. ↩ ↩²

[clayjohn]

Testing locally I can't see any visual regressions (tested with both a high res and low res shadow maps at varying max distances and varying camera distances).

I can confirm this fixes the stability of the 2 split variant. The fix makes sense as the 2 split variant uses a shadow map that is effectively twice as wide as the regular one.

It also makes sense that it wouldn't break the 4 split variant since 2 is a factor of 4

[akien-mga]

Thanks!