Created attachment 120976 [details] No artefacts when rendering FRONT and BACK There are bad artefacts when rendering via an FBO to FRONT with a blit. These are absent when rendering to both FRONT_AND_BACK buffers with a buffer swap. Environment: Linux Mint 17 (Linux 3.13.0-24-generic) Mesa 11.2.0 (via oibaf) HD6000 GPU Attached are two executables one with FBO rendering one without. The Mesa Intel linker takes two minutes to link so be patient. The very same executables work just fine with an Nvida GPU.
Created attachment 120977 [details] artefacts when rendering via FBO this is the second executable which exhibits the artefacts
Created attachment 120978 [details] shared library list This file shows the shared libraries used by these executables. Nothing special I think.
Created attachment 120979 [details] executable
People are not likely to run stray executables for a variety of reasons. apitraces (or source code) would be much preferable.
Comment on attachment 120976 [details] No artefacts when rendering FRONT and BACK Whoops, it's an executable! I've added it at the end.
(In reply to Matt Turner from comment #4) > People are not likely to run stray executables for a variety of reasons. > apitraces (or source code) would be much preferable. I understand Matt, but the source code is quite a large system and needs various large images to accompany it. I have embedded smaller images, the shaders etc. in the executable. Apitrace just crashes when I have tried it -- after building it from source -- so I'd be engaged in yet another debug. I'm sure you guys have a spare Linux machine that you use for crash purposes that isn't connected to your network? Back up the machine; unplug the RJ-45; do the tests; wipe the disk and restore. Or trust me. BTW, thanks for buying Altera.
Created attachment 120980 [details] parts of the rendering set up Source code for the rendering set up. Various modes are set depending on the driver found.
Created attachment 120983 [details] left good right bad The left side of the image is the result of rendering to both the FRONT and BACK buffers with a periodic swap. The right hand side is rendering via an FBO to the FRONT buffer. In the right hand side there are gridded dots of pixels both in solid areas and light areas which suggest the alpha channel is somehow corrupted. Rendering to an FBO is the preferred method and it works just fine with Nvidia.
Tried to reproduce issue using available part of source code. As it missing important parts of application it's impossible to observe mentioned issues (dotes) not from pre-compiled test. Behavior is identical with Intel, Radeon and Nvidia. So nothing to fix till exact sample to reproduce provided.
Thank you for working so hard on this issue. The FBO blitting turns out to be a red herring. My fragment shader is 'odd' in that is has large switch statement. This has caused the linking time to be rather long as reported in bug #91857 and, to my surprise, it also causes the artifacts I reported here and in bug #110424 I created a sample application (attached to #110424) that illustrates the problem. I'm afraid it will be troublesome to build, though it is a regular GCC build, but it is possible to reproduce the artifacts with it. The fragment shader's case statement has a #if ... #endif section that will enable/disable the artifact problem.
As attached to this bug source code didn't reproduce reported bug and later proper reproducer was attached in Bug 110424 I would close this bug as duplicate.
*** This bug has been marked as a duplicate of bug 110424 ***
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