https://bugs.freedesktop.org/show_bug.cgi?id=30002
--- Comment #8 from Marek Olšák maraeo@gmail.com 2010-09-04 14:44:20 PDT --- (In reply to comment #7)
(In reply to comment #1)
The handling of textures with a 0 width, height, or depth is an odd corner case in the spec, so it's not too surprising that it's not handled correctly.
"where ws, hs, and ds are the specified image width, depth, and depth, and wt, ht, and dt are the dimensions of the texture image internal to the border. If wt, ht, or dt are less than zero, then the error INVALID VALUE is generated. An image with zero width, height, or depth indicates the null texture. If the null texture is specified for the level-of-detail specified by texture parameter TEXTURE BASE LEVEL (see section 3.8.4), it is as if texturing were disabled."The last bit is the tricky part. You have to create the texture but disable texturing on any unit where it is bound. We could use a piglit test for this corner case.
Interesting. Should this be part of Gallium's API as well, or should we handle it one level up and make these textures illegal in Gallium? Does anybody know what Dx does?
Look at R5xx docs and that's pretty much what D3D9 does. If we had to implement a D3D9 driver, we'd be finished loooong ago. There is a set of samplers and you bind textures to those samplers. This is the low level function to create a texture:
http://msdn.microsoft.com/en-us/library/bb174363%28v=VS.85%29.aspx
It doesn't seem 0x0 textures are allowed, or meaningful. However if I had a choice, I would use this high level function:
http://msdn.microsoft.com/en-us/library/bb172800%28v=VS.85%29.aspx
Which explicitly states that if you request a 0x0 texture, you get a texture of size 1x1.
Anyway, I was looking into this issue and I am almost sure this is a bug in st/mesa and that the game doesn't actually create a zero-sized texture. IIRC, the mipmap setup is broken. In Tiny and Big, I get this failure:
state_tracker/st_texture.c:68:st_texture_create: Assertion `width0 > 0' failed.