Bug 10120

Summary:	Broken rendering in kpovmodeler when DRI disabled (using GLX only)
Product:	Mesa	Reporter:	Brice Goglin <brice.goglin>
Component:	GLX	Assignee:	mesa-dev
Status:	RESOLVED INVALID	QA Contact:
Severity:	normal
Priority:	medium
Version:	6.5
Hardware:	Other
OS:	All
URL:	http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=393150
Whiteboard:
i915 platform:		i915 features:

Description Brice Goglin 2007-02-28 02:59:11 UTC

This bug has been reported to the Debian BTS about 6 months ago by Alexandre Denis. It still apply to Mesa 6.5.2 and it seems it was already there in 6.4.2 (I couldn't test earlier mesa releases).

If you disable DRI on your X server, either by removing the corresponding DRI drivers, or by disabling dri explicitely in Xorg.conf, kpovmodeler rendering is completely broken.

To reproduce, start a second X server (so that DRI is disabled), open kpovmodeler and load /usr/share/apps/kpovmodeler/examples/scenes/advanced/ants.kpm (this is the path in Debian, it might need to be adapted for other distribs). There are 4 black rectangles in kpovmodeler's window. Each rectangle displays a wired rendering of a ant, here. But almost nothing is actually displayed.

If DRI is enabled, the rendering is fine. If software rasterizer libraries are installed instead of DRI/GLX, rendering is also fine (according to the reporter of the Debian bug, I did not test myself). So this looks completely specific to GLX, from what I understand in how GLX/DRI/soft-rasterize are organized.

thanks,
Brice

Comment 1 Roland Scheidegger 2007-02-28 05:46:24 UTC

This works for me (the ants demo, I've tried with LIBGL_ALWAYS_INDIRECT=1 which should have the same effect as not loading dri).
This was, however, with xorg 7.2 / mesa 6.5.2. Updating mesa alone won't help, as indirect rendering uses its own mesa library built into the xserver.

Comment 2 Michel Dänzer 2007-02-28 06:26:22 UTC

(In reply to comment #1)
> This works for me (the ants demo, I've tried with LIBGL_ALWAYS_INDIRECT=1 which
> should have the same effect as not loading dri).

Did you make sure AIGLX is disabled as well?

Comment 3 Brice Goglin 2007-02-28 06:35:23 UTC

Right, xserver-xorg-core 1.2.0 seems to be okay. So I guess the bug may be closed, sorry.

However, I am having a hard time trying to understand why upgrading the X server solves a problem that was apparently in Mesa. I was already kind of lost about what GLX without DRI does compared to software rasterizer. But, I am even more confused now :)

Thanks.

Comment 4 Philipp Klaus Krause 2007-02-28 06:41:53 UTC

You reported a bug in the software renderer. AFAIK LIBGL_ALWAYS_INDIRECT=1 does not have the same effect as not loading dri, at least not in 7.2. xorg 7.2 (in xserver-xorg-core 1.2.0) implements accelerated indirect rendering. So the bug may still lurk in software OpenGL, but since all rendering, even indirect rendering is accelerated you never see it.

Comment 5 Brice Goglin 2007-02-28 06:55:02 UTC

To make things clear:

I did _not_ try LIBGL_ALWAYS_INDIRECT=1, only Roland Scheidegger did.

I only tried in a second X server. DRI is enabled in xorg.conf, but it ends up being disabled because it is already enabled in the first X server. I see the rendering problem in the 2nd server when using 1.1.1, not with 1.2.0. So, from my point of view, upgrading to 1.2.0 fixes the problem.

Just to be sure, I will try on my other machine tonight (the one I initially reproduced the bug on, with a single X server and DRI libraries uninstalled). If this is ok, I'll close the bug.

Comment 6 Roland Scheidegger 2007-02-28 08:35:11 UTC

Sorry to add confusion, I didn't mention but had aiglx disabled. Even if not, the bug probably should have shown up if still present, since it was mentioned that it works with softare mesa, and thus the bug was deemed to be somewhere in glx protocol handling and not the renderer itself.

Comment 7 Brice Goglin 2007-02-28 10:13:35 UTC

I just tried on another machine with a single X server after uninstalling the DRI libs. Xserver 1.2.0 renders fine while 1.1.1 does not. Closing this bug as invalid then, sorry for the inconvenience.

If there is something we could backport in Xserver 1.1.1/Mesa 6.5.1 so that we can fix Debian Etch before it is released, please let us know.

Thanks.

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