Shadow related visual artifacts

[historic_bruno]

Example: ​http://i.imgur.com/TAZdt.jpg

When the sun is at low angles and shadows are enabled, there are faint box-shaped artifacts on the terrain. They change with the camera orientation, you might see them clearly or not at all. They are most easily noticed in actor viewer, because the terrain is white, but also visible if you paint a lighter colored terrain in the normal game view.

[historic_bruno]

Referred to as "shadow acne" in ​this article. Solutions:

• bounds on the near plane and the far plane for the light space view frustum should be calculated as tightly as possible
• slope scale-based depth bias and other types of bias are other solutions used to mitigate shadow acne (which we do with a fixed bias, but maybe we can improve our method?)

[historic_bruno]

Resolving as fixed by r12884. Though the above suggestions might be improvements, I can no longer reproduce the visual bug thanks to myconid's patch.