Re: [Mesa3d-users] Depth Buffering

[Brian P. <bri...@tu...>]

Lebsack, Eliot wrote:
> Good morning.
> 
> I've been studying this issue off and on for 2 years now,
> and have not been able to resolve it, so I figured I'd ask here.
> 
> I've been using Mesa within XFree86 and now xorg from RedHat
> Enterprise 3 and 4. By default, if I'm not using any special
> 3D hardware drivers, the glxinfo command will generally
> only provide contexts with 16-bit depth buffer support. I've tried
> to recompile XFree86 and Mesa so that it would use, say, 24 bits
> by changing the "DEFAULT_SOFTWARE_DEPTH_BITS" to 24 in the
> config.h file. However, this effect does not propagate into the
> compiled and installed software.
> 
> There is a reference in the FAQ to "DEPTH_BITS" being changed from
> 16 to 24 bits, but there is no further information. Furthermore, 
> when I search the code base (XFree86 and Mesa), I see no reference
> to DEPTH_BITS actually impacting the compiled depth buffer precision.
> 
> Has anyone else been able to change/increase their depth buffer
> precision from 16 to 24? If so, what is the proper procedure for
> doing this at compile time?

Unfortunately, fixing this involves changing some server-side GLX 
code.  The file in question is in the X.org tree at 
xserver/xorg/GL/mesa/X/xf86glx.c

There's a list of default GLX visuals to use when there's no hardware 
driver.  We'd need to add a new visual or two with deeper Z buffers.

I don't have time for this right now.  You could take a stab at it though.

I'm cc'ing Ian since he may be the last person who's worked on that code.

-Brian