ATi, Accessing texture level below TEXTURE_BASE

[Dan Bartlett]

Hi,
using Ati Mobility Radeon HD 5650 with Catalyst 11.8 drivers, I noticed that this causes an AV at the glTexImage2D call:

glGenBuffers(1, @PBO);
glBindBuffer(GL_PIXEL_UNPACK_BUFFER, PBO);
glBufferData(GL_PIXEL_UNPACK_BUFFER, twidth*theight*4, @data, GL_STATIC_DRAW);

glGenTextures(1, @tex);
glBindTexture(GL_TEXTURE_2D, tex);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_BASE_LEVEL, 1);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, twidth, theight, 0, GL_BGRA, GL_UNSIGNED_BYTE, 0);
It's unusual calling glTexImage for a level beneath GL_TEXTURE_BASE_LEVEL, but AFAICT shouldn't cause an AV.

Something else that causes an AV when it comes to render using a texture, is having GL_TEXTURE_MAX_LEVEL < GL_TEXTURE_BASE_LEVEL, eg.

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_BASE_LEVEL, 4);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, 1);
This is one of the listed checks of texture completeness, so should handle it cleanly rather than causing an AV.

[Alfonse Reinheart]

What is an AV?

[Dan Bartlett]

Sorry, AV = Access Violation.

[Hongwei Li]

Is it caused by glBufferData? I removed PBO stuff and found no AV in the glTexImage.See if upgrading to 11.9 works.

[Dan Bartlett]

The access violation "Access violation at 03E7C870 in module 'atioglxx.dll'. Read of address 00000000" occurs at the glTexImage2D call, but only when a buffer object is bound to GL_PIXEL_UNPACK_BUFFER.
eg. This doesn't throw an AV:


glBindBuffer(GL_PIXEL_UNPACK_BUFFER, 0);
glGenTextures(1, @tex);
glBindTexture(GL_TEXTURE_2D, tex);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_BASE_LEVEL, 1);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, twidth, theight, 0, GL_BGRA, GL_UNSIGNED_BYTE, 0);

and uploading to a level >= GL_TEXTURE_BASE_LEVEL works fine, but this throws an AV:



glGenBuffers(1, @PBO);
glBindBuffer(GL_PIXEL_UNPACK_BUFFER, PBO);
glBufferData(GL_PIXEL_UNPACK_BUFFER, twidth*theight*4, nil, GL_STATIC_DRAW); // nil = NULL equivalent

glGenTextures(1, @tex);
glBindTexture(GL_TEXTURE_2D, tex);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_BASE_LEVEL, 4);
// AV when (0 <= level < GL_TEXTURE_BASE_LEVEL)
glTexImage2D(GL_TEXTURE_2D, 2, GL_RGBA, twidth, theight, 0, GL_BGRA, GL_UNSIGNED_BYTE, 0);


The 2nd issue appears to be fixed, since:


glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_BASE_LEVEL, 4);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, 1);
no longer causes an AV on draw calls in 11.9, but correctly detects an incomplete texture + renders a white triangle.

Another issue with glTexImage2D when a PBO is bound is that if you try loading a high image level, you get an out of memory error (or potentially a very big texture allocated), which you don't get if no PBO is bound.


glGenBuffers(1, @PBO);
glBindBuffer(GL_PIXEL_UNPACK_BUFFER, PBO);
glBufferData(GL_PIXEL_UNPACK_BUFFER, twidth*theight*4, nil, GL_STATIC_DRAW);
// adding this line prevents out of memory error
// glBindBuffer(GL_PIXEL_UNPACK_BUFFER, 0);

glGenTextures(1, @tex);
glBindTexture(GL_TEXTURE_2D, tex);
//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_BASE_LEVEL, 9);
//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, 10);
glTexImage2D(GL_TEXTURE_2D, 10, GL_RGBA, 32, 32, 0, GL_BGRA, GL_UNSIGNED_BYTE, nil);
CheckOpenGLError(); // out of memory

[Hongwei Li]

Got it. I reproduced your bug in my machine. It is indeed a driver bug: some NULL pointer is referred when PBO and texture are used at the same time. Thanks for pointing it out. We'll fix it in the next version of catalyst driver.