Blender Git Loki

Eevee: Shadows: Add Receiver Plane Depth Bias

This bias replace the previous bias method. The bias is now scalled to
have the correct depth of the triangle at the sample location. This is done
by computing the actual depth that would be recorded in the shadowmap
at the texels locations, if the triangle was extrapolated.

This leads to less shadow acne and it ensure the bias is always the minimum
amount that ensure correct shadowing.

However this technique is not failure free and if the receiver is nearly
parallel to the light, the bias is nearly infinite and light leaking occurs.

For this reason I decided to cap the bias by the bias parameter to tweak
between shadow acne and light leaking.