GLSL Spec

Man I totally forgot to blog about this here.

I got really annoyed with the glsl spec. It’s full of definitions like this:

genType clamp(genType x,
  	genType minVal,
  	genType maxVal);

genType clamp(genType x,
  	float minVal,
  	float maxVal);

genDType clamp(genDType x,
  	genDType minVal,
  	genDType maxVal);

Once you know that:

• genType = float, vec2, vec3, vec4
• genDType = double, dvec2, dvec3, dvec4

It is easy to read as a human, but inaccurate as a machine. The reason is that we see that when we call clamp with two floats we get a float, and when given 2 vec2s we will get a vec2. But when trivially parsed it looks like clamp returns some generic type. This is false. Say we have some function foo(vec2), in glsl this is legal:

foo(clamp(vec2(1,2), vec2(2,3));

Because the return type of clamp is concrete, it’s only the spec has compressed this information for ease of reading.

This may seem like a really tedious rant, but to me it’s super important as it make it more complicated to use this data, and I havent even started on the fact that the spec is only available as inconsistantly formatted html man pages or PDF.

What I wanted was a really specification for the functions and variables in glsl. Every single overload, specified in the types of the language.

The result of this need is the glsl-spec project which has exactly what I wanted. Every function, every variable, specified using GLSL types, with GL version info, and available as s-expressions & json.

Let’s go make more things

Peace