Preventing webgl glsl automatically inlining functions?

Question

In my GLSL code, I have large functions being called multiple times.

As an example, inside my perlin noise function I run a hash function many times.

float perlinNoise (...) {
    ...
    float x0y0z0 = pcgUnit3(seedminX,seedminY,seedminZ);
    float x0y0z1 = pcgUnit3(seedminX,seedminY,seedmaxZ);
    float x0y1z0 = pcgUnit3(seedminX,seedmaxY,seedminZ);
    float x0y1z1 = pcgUnit3(seedminX,seedmaxY,seedmaxZ);
    float x1y0z0 = pcgUnit3(seedmaxX,seedminY,seedminZ);
    float x1y0z1 = pcgUnit3(seedmaxX,seedminY,seedmaxZ);
    float x1y1z0 = pcgUnit3(seedmaxX,seedmaxY,seedminZ);
    float x1y1z1 = pcgUnit3(seedmaxX,seedmaxY,seedmaxZ);
    ...
}

In my procedural generation algorithm, I call the perlin noise function multiple times.

I notice that for every time I add a call to the perlin noise function, the compile time for the shaders takes longer. I think the problem is that glsl inlines the function calls, and thereby the shader code becomes very large.

Am I correct about the inlining, and if so, how do I prevent it from happening?

nabr nabr · Accepted Answer · 2019-02-17T21:30:18

On page 13 of the GLSL_ES_Specification_1.00 it is described, how to set pragma derectives

#pragma optimize(off)
#pragma debug(on)

That would be the "inlining" case. "Am I correct about the inlining ..". For my knowlenge, no. Also not quite sure what is happening in the background. On Windows it gets transpiled to ANGEL, maybe have a look at the source could help.

In general: try to lower the precession, consider that three digits 1.000 could be "nice" enough. Floats can only store 5 -6 digits anyway. Avoid branching. That should be the First Aid Kid.

Some debugger tools out in the wild (please make your own research)

Optimizer

https://zz85.github.io/glsl-optimizer/

Preventing webgl glsl automatically inlining functions?

1 Answers