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OpenGL & Vulkan

Journeyman III

Strange behavior when converting GL_INT_2_10_10_10_REV attribute to vec3

I'm getting some really strange behavior when using attributes of the GL_INT_2_10_10_10_REV format in my OpenGL application. It could be related to this issue. I'm testing this on a Radeon R7, running the 21.5.2 driver on Windows 10. I believe it's a new bug, because it broke the application I was working on after I updated my drivers.

The bug is triggered by using the GL_INT_2_10_10_10_REV format for a vertex attribute and using just the xyz-components of that attribute — either by declaring it as a vec3, or by declaring it as a vec4 and then extracting the xyz parts explicitly. The bug causes other, unrelated vertex shader outputs to become corrupted.

I've got a small program that reproduces the bug (download here). It's a stand-alone .exe with 223-line C++ source included. (Requires a C++11 compiler, SDL2, and GLEW to build.) The program renders the classic three-color OpenGL test triangle. The triangle vertices have position and color attributes, which are set up like so:

glVertexAttribPointer(0, 4, GL_INT_2_10_10_10_REV, GL_TRUE, 8, (void*) 0); // Position.
glVertexAttribPointer(1, 4, GL_UNSIGNED_BYTE, GL_TRUE, 8, (void*) 4); // Color.

The triangle is rendered twice, first with a shader that assigns the position directly to gl_Position, like so:

layout(location=0) in vec4 aPosition;
layout(location=1) in vec4 aColor;
out vec4 vColor;

void main()
    gl_Position = aPosition;
    vColor = aColor;

The second triangle is rendered with an otherwise identical shader that uses only the xyz parts of the position attribute, setting w to 1:

gl_Position = vec4(, 1.0);

The input vertices all have a w-coordinate of 1, so the behavior of the two shaders should be identical. The actual behavior, on my machine, is that the first triangle renders correctly, but the second triangle is completely red:



Running the program in RenderDoc, I get a black triangle instead:



From RenderDoc's mesh viewer I can tell that the input vertex data looks okay, but in the vertex shader output for the second triangle, the colors are all zero!



I would guess it's some general bug involving the way GL_INT_2_10_10_10_REV attributes are fetched or decoded; this is just the simplest way I've found to reliably trigger it.

My workaround for now is to always declare attributes of that type as vec4, and to forgo any swizzling or conversion to vec3 in the vertex shader. I would really like to see this fixed though — if nothing else so that nobody else has to be tripped up by this.

3 Replies
Big Boss

Hi @eltopo ,

Thank you for reporting it.

I'm testing this on a Radeon R7, running the 21.5.2 driver on Windows 10.

Adrenalin 21.5.2 is an old driver. Can you please try the latest driver to see if the above issue is still reproducible?

The latest Adrenalin driver is available here: Adrenalin 21.9.2 

By the way, I ran the repro program with a recent driver, however I didn't observe the above issue. Attached screenshot is the program output that I got.

Another point to note. Radeon R7 products are now under the legacy support model, so no additional driver release is planned for these products. For more information, please check here: AMD Radeon™ Software Support for Legacy Graphics Products 



The "auto-detect" installer from the drivers section of the site installs the 21.5.2 version of the driver. When I check for updates, it tells me it's up to date. Running the 21.9.2 installer gives me

Error 182 – Radeon Software install detected AMD graphics hardware in your system configuration that is not supported with this software installation.

So I guess that means I'm stuck with the legacy driver? If so, that's frustrating, because I don't think this issue was present in the older driver version.


Yes, if you are using any legacy product like Radeon R7, then you need to install Adrenalin 21.5.2 or older drivers. These legacy products are not supported by the recent graphics drivers starting with Adrenalin 21.6.1.

[Product and OS Support Update for Radeon Software Adrenalin 21.6.1 ]