Re: [Mesa3d-users] Intel driver depth buffer

[Peter C. <pc...@ca...>]

On Fri, 2007-11-30 at 15:02 -0700, Brian Paul wrote:
> Peter Clifton wrote:
> > Hi,
> > 
> > I'm having some strange (seemingly) depth buffer related issues running
> > VTK.
> > 
> > I've got the Intel X driver version 2.1.0 (+ Ubuntu Gutsy patches), and
> > mesa version 7.0.1 (Ubuntu Gutsy - might have some patching).
> > 
> > When I run a simple test program:
> > 
> > MESA_DEBUG=1 ipython -wthread vtk_test.py
> > 
> > Where vtk_test.py is from the first example here:
> > http://scipy.org/Cookbook/MayaVi/mlab
> > 
> > I get this warning:
> > Mesa warning: glEnable(GL_DEPTH_TEST) but no depth buffer
> 
> It means your window wasn't created with a Z/depth buffer, but the 
> program is trying to enable/use depth buffering.

I've got that far poking through sources, but it didn't help me fix it
yet!

> My guess is there's a bug somewhere in the python code related to GL and 
> window creation.

The visual seems to be chosen with:

    glXChooseVisual( dpy, DefaultScreen(dpy), attribList )

I've not got to rebuilding wx widgets with debug printf to verify what
this returns, but its probably my next step in trying to understand the
issue.

Only in the case where stereo is explicitly requested, does the VTK
viewer explicitly ask for a depth buffer, normally a default attribList
is made. (Although reading around the code, it seems the default is to
request a >1 bit depth buffer).

I've tried explicitly setting a requirement for a 16 / 32 bit Z buffer,
and it didn't seem to help.

> Do other OpenGL apps (or demos like glxglears) seem OK?

They seem fine, although glxgears isn't a good test for depth surely,
being flat? Other apps seem OK, so its probably Wx's / wxPython's fault,
as you say.

glxinfo reports plenty of depth-buffer capable visuals:
   visual  x  bf lv rg d st colorbuffer ax dp st accumbuffer  ms  cav
 id dep cl sp sz l  ci b ro  r  g  b  a bf th cl  r  g  b  a ns b eat
----------------------------------------------------------------------
0x23 24 tc  0 32  0 r  y  .  8  8  8  8  0  0  0  0  0  0  0  0 0 None
0x24 24 tc  0 32  0 r  .  .  8  8  8  8  0  0  0  0  0  0  0  0 0 None
0x25 24 tc  0 32  0 r  y  .  8  8  8  8  0 24  8  0  0  0  0  0 0 None
0x26 24 tc  0 32  0 r  .  .  8  8  8  8  0 24  8  0  0  0  0  0 0 None
0x27 24 tc  0 32  0 r  y  .  8  8  8  8  0  0  0 16 16 16 16  0 0 Slow
0x28 24 tc  0 32  0 r  .  .  8  8  8  8  0  0  0 16 16 16 16  0 0 Slow
0x29 24 tc  0 32  0 r  y  .  8  8  8  8  0 24  8 16 16 16 16  0 0 Slow
0x2a 24 tc  0 32  0 r  .  .  8  8  8  8  0 24  8 16 16 16 16  0 0 Slow
0x2b 24 dc  0 32  0 r  y  .  8  8  8  8  0  0  0  0  0  0  0  0 0 None
0x2c 24 dc  0 32  0 r  .  .  8  8  8  8  0  0  0  0  0  0  0  0 0 None
0x2d 24 dc  0 32  0 r  y  .  8  8  8  8  0 24  8  0  0  0  0  0 0 None
0x2e 24 dc  0 32  0 r  .  .  8  8  8  8  0 24  8  0  0  0  0  0 0 None
0x2f 24 dc  0 32  0 r  y  .  8  8  8  8  0  0  0 16 16 16 16  0 0 Slow
0x30 24 dc  0 32  0 r  .  .  8  8  8  8  0  0  0 16 16 16 16  0 0 Slow
0x31 24 dc  0 32  0 r  y  .  8  8  8  8  0 24  8 16 16 16 16  0 0 Slow
0x32 24 dc  0 32  0 r  .  .  8  8  8  8  0 24  8 16 16 16 16  0 0 Slow
0x56 32 tc  0 32  0 r  .  .  8  8  8  8  0  0  0  0  0  0  0  0 0 Ncon

The one thing which is odd, is the Xorg.0.log file has:

(WW) AIGLX: 3D driver claims to not support visual 0x23
(WW) AIGLX: 3D driver claims to not support visual 0x24
(WW) AIGLX: 3D driver claims to not support visual 0x25
(WW) AIGLX: 3D driver claims to not support visual 0x26
(WW) AIGLX: 3D driver claims to not support visual 0x27
(WW) AIGLX: 3D driver claims to not support visual 0x28
(WW) AIGLX: 3D driver claims to not support visual 0x29
(WW) AIGLX: 3D driver claims to not support visual 0x2a
(WW) AIGLX: 3D driver claims to not support visual 0x2b
(WW) AIGLX: 3D driver claims to not support visual 0x2c
(WW) AIGLX: 3D driver claims to not support visual 0x2d
(WW) AIGLX: 3D driver claims to not support visual 0x2e
(WW) AIGLX: 3D driver claims to not support visual 0x2f
(WW) AIGLX: 3D driver claims to not support visual 0x30
(WW) AIGLX: 3D driver claims to not support visual 0x31
(WW) AIGLX: 3D driver claims to not support visual 0x32

Which would leave only visual 0x56, which has no depth buffer.
(What is Caveat: Ncon?) Are these warnings just spurious, or do I have
config problem which might relate to the Z-Buffer issue?

I remember looking up these warnings before, but not finding much
conclusive about their cause / severity.

Thanks for replying,

Best wishes,

-- 
Peter Clifton

Electrical Engineering Division,
Engineering Department,
University of Cambridge,
9, JJ Thomson Avenue,
Cambridge
CB3 0FA

Tel: +44 (0)7729 980173 - (No signal in the lab!)