c++ - OpenGL Uniform Functions - Why so many? -

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why there many functions set uniforms?

gluniform1f    gluniform2f    gluniform3f    gluniform4f gluniform1fv   gluniform2fv   gluniform3fv   gluniform4fv gluniform1i    gluniform2i    gluniform3i    gluniform4i gluniform1iv   gluniform2iv   gluniform3iv   gluniform4iv gluniform1ui   gluniform2ui   gluniform3ui   gluniform4ui gluniform1uiv  gluniform2uiv  gluniform3uiv  gluniform4uiv  gluniformmatrix2fv  gluniformmatrix2x3fv  gluniformmatrix2x4fv gluniformmatrix3fv  gluniformmatrix3x2fv  gluniformmatrix3x4fv gluniformmatrix4fv  gluniformmatrix4x2fv  gluniformmatrix4x3fv

i think way data uploaded vertex , element buffers waaay better, since don't have call different function different type. why case uniforms? there possibility use 1 function, can pass pointer?

hindsight 20/20 , choice done in line other functions take vectorial data in various types , dimensionality. i'm referring glvertex… of course. initial reason pass value was, on architectures there enough registers around more efficient pass value in register. compilers optimize preceding operations end right values in right register.

opengl descendant of irixgl developed sgi graphics workstations , irix os. these workstations used mips architecture. , calling convention mips (https://en.wikipedia.org/wiki/calling_convention#mips)

the commonly used[5] calling convention 32 bit mips o32[6] abi passes first 4 arguments function in registers $a0-$a3; …

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the n32 , n64 abis pass first 8 arguments function in registers $a0-$a7; …

so there have it: on mips it's quite sensible choice pass vec4 elements per value. in irixgl , opengl-1.0 there no vertex arrays , you'd have make lots of glvertex calls.


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