Convert Single-Pass Stereo from HLSL to GLSL about slang

[tangent-vector]

Just to make sure I get it: NV_X_RIGHT and NV_VIEWPORT_MASK are HLSL semantics, yes? So I need to convert uses of shader outputs with those semantics into uses of the corresponding GLSL builtins.

Do we know if glslang supports the extension?

[nbentyNV]

Yes.

https://github.com/KhronosGroup/glslang/commits/master?author=chaoc

[tangent-vector-personal]

I've looked into this a bit:

• The main challenge is that the mask output is a vector in HLSL, but an (unsized) array in GLSL

• A secondary challenge is that the mask is given type uint in HLSL and int in GLSL

• A tertiary challenge is that the HLSL extension just adds a second "right eye" output, and still uses SV_Position while the GLSL extension seems to replace gl_Position with an array of outputs

These are all surmountable, but require a bit more infrastructure for dealing with mapping system-value semantics to gl_* variables that may not match exactly in type.

[tangent-vector-personal]

Implemented in #129

[tangent-vector]

Reopening. My current implementing is totally bogus.

[tangent-vector]

Closing. There is no demand from current users for single-pass stereo.