OpenGL - sampler array limit?

Question

I have two sampler arrays in my fragment shader:

uniform sampler2D shadowMaps[12];
uniform samplerCubeShadow shadowMapsCube[12];

This works fine on my pc with opengl 4.2, however on my laptop (opengl 3.1) I'm getting the error 'array size too big'.

If I set it to 8, it works fine. Arrays of other types can be far larger however, and I can add more sampler arrays with a max size of 8 without a problem. So, how is this limit determined?

After lowering the array size to 8 the compilation works, but the linking fails silently (The log is empty and glGetError() returns 0).

If I declare each sampler individually (uniform sampler2D shadowMap1;uniform sampler2D shadowMap2; etc.), neither of these errors occur.

Answer 1

You have to take two things into account.

First, bear in mind that depending on your OpenGL version, accessing to samplers array using variables inside loops is not permited. See: https://stackoverflow.com/a/12031821/988027

Secondly, quoting from the OpenGL wiki page, there are a maximum amount of texture units you can use at the same time:

OpenGL contexts have a maximum number of texture image units, queriable from the constant GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS​.

Probably, this answer will help you. Particularly, have a look at the shader resource limitations.