Open-Source GPU Drivers Causing Headaches In KDE 4.5

[smitty3268]

Also, I should mention they aren't even 'requiring' the use of OpenGL2. That's what started this whole mess, is that they are trying to fallback to 1.x but failing because the drivers say they work with 2. They'll even fall further down into XRender and non-composited mode if they are able to detect problems, and that's the current issue.

[smitty3268]

Again, they are mostly concerned with getting a forward-compatible GL2 version working. That's so they can also run it on mobile devices, and get all the GLSL goodness that 2.0 brings.

The 2 pieces of OpenGL 3 that were mentioned on his blog were:

FBOs, which are already in the open drivers. Also, they have a wrapper around their use, so it transparently falls back on drivers which don't support them. (unless, of course, the drivers lie and simply crash)

Geometry shaders - this sounded much more speculative, and would likely only be used in a couple fancy effects, accompanied with alternatives to run on older versions that might be slightly lower quality if necessary.

[deanjo]

With the fucking intel driver it still doesn't work properly(and I'm using latest graphic stack from git). With latest stable intel driver I even cannot start kde to disable compositing!

Log in without starting X, use nano or your favorite editor to open ~/.kde4/share/config/kwinrc, look for the section called [Compositing] and look for the line saying Enabled=true and change that to Enabled=false, reboot or start X and your in.

[marek]

And a slightly off-topic question: does Mesa implement the noise*() functions for GLSL?

No, it doesn't, since proprietary drivers don't implement it either. A driver is allowed to return 0.5.

[BlackStar]

And a slightly off-topic question: does Mesa implement the noise*() functions for GLSL?

[BlackStar]

DDX and DDY are already in GLSL 1.1.

Oops, just checked the specs and you are right. Although I kinda question their usefulness, since you 1.1 doesn't offer texture*Grad functions.

Fake edit to my previous post:
- "in" and "varying" should obviously be "in" and "out"
- texture*Lod should be texture*Grad. The former exists since GLSL 1.1 (maybe earlier) and allows you to select the mipmap level, but it's the latter that allows you to specify the gradients explicitly (necessary for artifact-free parallax mapping, for instance).

[marek]

GLSL 1.3 renames the "attribute" and "varying" keywords to "in" and "varying", respectively, in order to make room for more shader stages (geometry, etc). It also introduces derivatives (ddx, ddy), a few new texture functions (texture*lod that allows you to control the mipmap it samples from), deprecates built-in uniforms, modifies the syntax for fragment output for easier MRT and adds a couple of new keywords (meant for OpenGL ES compatibility).

DDX and DDY are already in GLSL 1.1.

[darkbasic]

Well, with radeon (R600c/g) and mesa git I even didn't noticed they raised the opengl requisites. It just worked.
With the fucking intel driver it still doesn't work properly(and I'm using latest graphic stack from git). With latest stable intel driver I even cannot start kde to disable compositing!

[BlackStar]

What's the difference between GLSL 1.2 and 1.3? I'm simply guessing that's why they are going OpenGL 3?

GLSL 1.3 renames the "attribute" and "varying" keywords to "in" and "varying", respectively, in order to make room for more shader stages (geometry, etc). It also introduces derivatives (ddx, ddy), a few new texture functions (texture*lod that allows you to control the mipmap it samples from), deprecates built-in uniforms, modifies the syntax for fragment output for easier MRT and adds a couple of new keywords (meant for OpenGL ES compatibility).

Again, none of those features is necessary - or even useful - to desktop composition. I can understand kwin wanting a GL3-compatible codebase for future work but I will be very surprised if it offers any new functionality (over GL2) in the immediate future. I certainly cannot see them dropping 50% of their user-base for no tangible benefit.

[V!NCENT]

What's the difference between GLSL 1.2 and 1.3? I'm simply guessing that's why they are going OpenGL 3?