WebgL2: the case for Reversed Depth Range

[Kuranes]

Reversed depth range is a great feature allowing for much better zbuffer precision.

In practice it means less z-figthing, better ssao, better shadow map, better screen space raytrace, etc.

• Math explanation here "the reversed-Z mapping is basically magic": https://developer.nvidia.com/content/depth-precision-visualized

• Screenshot comparisons: https://mynameismjp.wordpress.com/2010/03/22/attack-of-the-depth-buffer
  Also has a D3D11 demo showing inversed depth range, see the windows test app PrTEST.zip
  ( source code is in the zip)

• OpenGL ES 3.0 does support it, see https://www.khronos.org/opengles/sdk/docs/man3/html/glDepthRangef.xhtml

(linked issue #543 (comment))

[Kuranes]

(reversed depth trick need in fact desktop OpenGL widely-supported ARB_clip_control extension (now also core in OpenGL 4.5 as glClipControl). Unfortunately, in GL ES you're out of luck.)