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Some of my vertex attributes are single unsigned bytes, I need them in my GLSL fragment shader, not for any "real" calculations, but for comparing them (like enums if you will). I didnt find any unsigned byte or even byte data type in GLSL, so is there a way as using it as an input? If not (which at the moment it seems to be) what is the purpose of GL_UNSIGNED_BYTE?
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vec3 is a floating point vector with three components. It can be initialized by: Providing a scalar value for each component. Providing one scalar value. This value is used for all components.
HLSL is analogous to the GLSL shading language used with the OpenGL standard. It is very similar to the Nvidia Cg shading language, as it was developed alongside it. Early versions of the two languages were considered identical, only marketed differently.
One way to speed up GLSL code, is by marking some variables constant at compile-time. This way the compiler may optimize code (e.g. unroll loops) and remove unused code (e.g. if hard shadows are disabled). The drawback is that changing these constant variables requires that the GLSL code is compiled again.
GLSL doesn't deal in sized types (well, not sized types smaller than 32-bits). It only has signed/unsigned integers, floats, doubles, booleans, and vectors/matrices of them. If you pass an unsigned byte as an integer vertex attribute to a vertex shader, then it can read it as a uint type, which is 32-bits in size. Passing integral attributes requires the use of glVertexAttribIPointer/IFormat (note the "I").
The vertex shader can then pass this value to the fragment shader as a uint type (but only with the flat interpolation qualifier). Of course, every fragment for a triangle will get the same value.
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