shadermagic

shadermagic is a crate I wish existed. Think Therkla's hlslparser, but rust native.

shadermagic pretend to be a compiler from pseudo-glsl to different glsl variants and Metal's MSL.

If you want something that actually works, check naga, spirvcross, sokol-shdc, glslang, glslcc, hlsl parser, hlslparser fork or even nanoshredder.

Another relevant case study is this emscripten hack. shadermagic is a slightly more advanced version of the same idea.

shadermagic takes some undocumented almost #version 130 shader and apply a ton of String::replace to make plain version 100, version 100 with webgl1 extensions, 130, 330, 300 es and metal's MSL.

Metal is a bit of a special case, with a bit of extra code on top of String::replace. But it is still very sipmple string manipulations. shadermagic knows nothing about AST and shaders semantics.

shadermagic will never work well on arbitary glsl input. No amount of string::replace could replace a compiler. However, it might be possible to design shaders specifically for shadermagic, and it might take less work than hand-writing for each target. Or not! I really hope I put enough warnings here.

How to make glsl->metal works

Enough with warnings, tips to keep this bunch of hacks afloat:

• don't access uniforms outside the main() function, pass them as arguments.
• put the main function last, after everything else in the shader
• annotate attribute in the vertex shader with // [[attribute(N)]]
• annotate varying in the vertex/fragment shader with // [[user(locnN)]]
• avoid functions with the same names in vertex/fragment shaders
• remember that String::replace is very stupid and does not take any context into account. Avoid naming things like "mymat3", avoid things like "BaseColor" and "Color". Yes, this is that bad.
• avoid .s/.t/.p/.q, use .x/.y/.z/.w instead