Element exceeds maximum supported number of combined texture image units

[Danjb]

Hello,

I have just set up a debug message callback, and I'm seeing lots of these errors:

[LWJGL] OpenGL debug message
	ID: 0x501
	Source: API
	Type: ERROR
	Severity: HIGH
	Message: GL_INVALID_VALUE error generated. Element exceeds maximum supported number of combined texture image units.

I have only created 6 textures, and I am only binding 1 at a time. When I print the value of glGetInteger(GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS) I get 192, so I don't understand what limit I am hitting here.

Can anyone please offer some insight?

Thanks,
Dan

[KaiHH]

The first step is to identify, which GL call caused this error. If you are using LWJGL 3, then the easiest way is to start your JVM with the LWJGLX/debug agent: https://github.com/LWJGLX/debug
You can download it directly from here: https://build.lwjgl.org/addons/lwjglx-debug/lwjglx-debug-1.0.0.jar
Then start the JVM with the JVM argument -javaagent:/path/to/lwjglx-debug-1.0.0.jar and you should see a stack trace when you hit the error.

[Danjb]

Thank you so much, that was really helpful.

The problem was that I was doing this:

glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, textureId);
glUniform1i(uniformLoc, GL_TEXTURE0);

Instead of this:

glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, textureId);
glUniform1i(uniformLoc, 0);

GL_TEXTURE0 has the value 33984, whereas samplers have to have a value in the value [0, GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS).
(Source: https://www.khronos.org/opengl/wiki/Texture#Samplers)

Thanks again.
Dan