Created attachment 89432 [details] test case Hello, I'm the lead programmer of game "Warsow" - an open source first person shooter. We just tried running development version of the game with open source AMD drivers shipped with Ubuntu 13.10 and custom-installed 3.12 Linux kernel. While the performance was better than we had expected, there were a few visual glitches. In the game we use the so called "hardware skinning" for skeletal models to transform vertex coordinates by the influencing bones on the GPU. The transformation code is pretty complex and involves quaternion maths and accessing uniform arrays by index read from vertex attribute. Despite the fact that vertex shader compiles successfully, the end result looks quite a bit off, meaning that sometimes meshes look deformed in unexpected directions. Unfortunately I can't take a screenshot to demonstrate the bug right now, but I managed to cook a somewhat minimal version of the shader. You will find the aforementioned transformation code in function QF_VertexDualQuatsTransform. If you need to access our repository to be able to reproduce and observe the bug, just let me know. Best regards, Victor
Does this occur only on AMD GPUs, or does it occur on other GPUs as well? If it does only occur on Radeons, are there specific ones? The issue could either be in the Radeon-specific back-end code or in the main compiler.
Tried to reproduce this on a few machines with different hardware and I came to the conclusion that Mesa and/or drivers in fact have got nothing to do with the bug. The wrong transformation was in fact caused by an embarrassing bug in our dual quaternion to matrix conversion code which only manifested itself when the program executed the software fallback branch of code, which happened to be caused by Mesa reporting GLSL version lower than 1.40. Sorry for wasting your time on this.
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