Identifying Uniform buffer in a GLSL shader

Question

I use glGetActiveUniform to query uniforms from the shaders.But I also use uniform buffers (regular and std140).Querying them returns an arrays with the primitive type of the uniform in the buffer.But I need a way to identify those are uniform buffers and not uniforms. Examples of uniform buffers in a shader:

layout(std140, binding = LIGHTS_UBO_INDEX) uniform LightsBuffer {

   LightInfo  lights[MAX_LIGHTS];

};

Is it possible to query only buffers from GLSL shader?

Andon M. Coleman Andon M. Coleman · Accepted Answer · 2015-02-10T22:04:01

Technically, what you actually have here is a uniform block. It has a name, but no type; its members (which are uniforms) have types, and I think that is what you are actually describing.

It is a pretty important distinction because of the way program introspection works. Using OpenGL 4.3+ (or GL_ARB_program_interface_query), you will find that you cannot query a type for GL_UNIFORM_BLOCK interfaces.

glGetActiveUniformBlockiv (...) can be used to query information about the uniform block, but "LightsBuffer" is still a block and not a buffer. By that I mean even though it has an attribute called GL_BUFFER_BINDING, that is really the binding location of the uniform block and not the buffer that is currently bound to that location. Likewise, GL_BUFFER_DATA_SIZE is the size of the data required by the uniform block and not the size of the buffer currently bound.

Identifying Uniform buffer in a GLSL shader

1 Answers