GL_FRAMEBUFFER_INCOMPLETE_DUPLICATE_ATTACHMENT_EXT errors - opengl

Question

I'm using FBOs in my OpenGL code and I'm seeing compilation errors on GL\_FRAMEBUFFER\_INCOMPLETE\_DUPLICATE\_ATTACHMENT\_EXT. What's the cause of this and how do I fix it?

Answer 1

The cause of this error is an older version of NVIDIA's glext.h, which still has this definition. Whereas the most recent versions of GLEW don't. This leads to compilation errors in code that you had written previously or got from the web.
The GL_FRAMEBUFFER_INCOMPLETE_DUPLICATE_ATTACHMENT_EXT definition for FBO used to be present in the specification (and hence in header files). But, it was later removed. The reason for this can be found in the FBO extension specification (look for Issue 87):
(87) What happens if a single image is attached more than once to a
framebuffer object?
RESOLVED: The value written to the pixel is undefined.
There used to be a rule in section 4.4.4.2 that resulted in
FRAMEBUFFER_INCOMPLETE_DUPLICATE_ATTACHMENT_EXT if a single
image was attached more than once to a framebuffer object.
FRAMEBUFFER_INCOMPLETE_DUPLICATE_ATTACHMENT_EXT 0x8CD8
* A single image is not attached more than once to the
framebuffer object.
{ FRAMEBUFFER_INCOMPLETE_DUPLICATE_ATTACHMENT_EXT }
This rule was removed in version #117 of the
EXT_framebuffer_object specification after discussion at the
September 2005 ARB meeting. The rule essentially required an
O(n*lg(n)) search. Some implementations would not need to do that
search if the completeness rules did not require it. Instead,
language was added to section 4.10 which says the values
written to the framebuffer are undefined when this rule is
violated.
To fix this error, remove all usage of GL_FRAMEBUFFER_INCOMPLETE_DUPLICATE_ATTACHMENT_EXT from your code.
If this isn't possible in your setup, then add a dummy definition to your glext.h or glew.h file like this:
#define GL_FRAMEBUFFER_INCOMPLETE_DUPLICATE_ATTACHMENT_EXT 0x8CD8