Timothy Lochner

glBindTextures will bind by texture unit. No guarantee that layout(binding) is the same as texture unit. In fact, glUniform1i allows you to change the texture unit for the uniform at a given location. https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glBindTextures.xhtml …

https://www.khronos.org/registry/OpenGL/extensions/ARB/ARB_shading_language_420pack.txt … "The identifier binding specifies which unit will be bound."

Hmm... I missed that. So next question, how do I introspect the shader to get that value? (ie, in c++ I don't want to hard-code it to 3).

see this family of functions https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glGetProgramResource.xhtml …

I was just looking at it when trying to find something that would get me the same result as glGetUniform1i, except in the glProgramX pattern, like glProgramUniform1i. It's not clear to me how to use the functions to get that value.

hopefully this will help as I don't 100% understand the problem, but I did a bit of shader reflection in my program and what I do is use glGetProgramInterfaceiv to build a map of uniforms and locations, that I can then use later with my shader object

relevant functions: glGetProgramInterfaceiv, glGetProgramResourceiv, glGetProgramResourceName would share code but it's not C/C++

building a map of name->bindpoints is exactly what I'm doing. Then I can take all the resources used for a particular drawcall, create arrays I can pass to glBindTextures/glBindSamplers/glBindImageTextures, and use those.