OpenGL multiple Sampler2D (array) examples?

Question

I find it surprisingly frustrating that it is so difficult to find examples of sampler2d arrays such as

uniform sampler2D myTextureSampler[5];

How would one store the uniform location of this?:

gl.GetUniformLocation(program, "myTextureSampler")

Would one simply use:

gl.GetUniformLocation(program, "myTextureSampler[0]")
gl.GetUniformLocation(program2, "myTextureSampler[2]")

How would one go about using multiple textures like this:

gl.BindTexture(gl.TEXTURE_2D, 1)
gl.BindTexture(gl.TEXTURE_2D, 2)

etc..

gl.ActiveTexture(gl.TEXTURE0)
gl.ActiveTexture(gl.TEXTURE1)

etc..

Note: this code is not pure c++ opengl. Just looking for the basic concept on how it would be done.

A simple example of passing, getting uniform location for a sampler2d array would be great. Does anyone have experience with this stuff?

Answer 1

I presume it's the same as all other shader array accesses and that:

glGetUniformLocation(program, "myTextureSampler[0]");

will work.

To use multiple textures you should set the slot which you want to put your texture in to active first:

glActiveTexture(GL_TEXTURE0);

and then you can bind your texture:

glBindTexture(GL_TEXTURE_2D, texture.handle);

The second parameter is the handle you got from glGenTextures().

Then you match the sampler2D with the appropriate texture by calling:

glUniform1i(location, 0);

The first parameter is the location you got back from calling glGetUniformLocation(). The second parameter is the active texture slot (GL_TEXTURE0 in this case).

Answer 2

The current answer has been here for a long time, but is not correct.

What you are using is uniform arrays.

For a shader declaration like:

uniform sampler2D myTextureSampler[5];

...you get the uniform location of the array, without specifying a subscript:

glGetUniformLocation(my_uniform, "myTextureSampler");

...then set its values in a single operation from an array:

GLfloat values[5] = {1.0f, 2.0f, 3.0f, 4.0f, 5.0f};
glUniform1fv(my_uniform, 5, values);

Documentation: https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glUniform.xhtml