Re: [Mesa3d-users] Does "Brian Paul" GL_VEND non-software implementations?

[Brian P. <br...@va...>]

Dave Morse wrote:
> 
> I'd like to discriminate between 100% software mesa, and the various
> hardware accellerated versions.  My plan is (vaugely) to use GL_VENDOR and
> GL_RENDERER strings.  I've seen:
> 
>   Stock RH6.2, software:
>   GL_VENDOR "Brian Paul"
>   GL_RENDERER "Mesa X11"
> 
>   Stale DRI:
>   GL_VENDOR "VA Linux Systems, Inc."
>   GL_RENDERER "Mesa DRI VoodooBanshee 20000821"
> 
>   Debian Potato, software (iirc):
>   GL_VENDOR "Brian Paul"
>   GL_RENDERER "Mesa Indirect" (+- a few chars)
> 
> So "Mesa" leading GL_RENDERER doesn't imply all software.  But it seems
> that the vendor "Brian Paul" only "sells" pure software implementations?
> 
> Maybe someone with more datapoints could straighten me out on how to test
> for pure software?

The first and last cases are pure software rendering.  The first is
"stand-alone" Mesa and the last is the OpenGL renderer built into the
XFree86 X server.


> Why do I want to do this?
> 
> Well, there are two operations that seem fine on hardware that turn out to
> be slow with mesa:
> 
> Drawing 300x200 alpha blended clouds.    (substitute GL_ALPHA_TEST > 0.5)
> Drawing a 640x480 smooth shaded polygon. (substitute glClear)

This has been discussed dozens of times over the years but here's the
key thing to remember:  the question isn't "will this OpenGL operation
be rendered with software or hardware" but "will this OpenGL operation
be at least a certain speed".  Consider using an old Voodoo1 card with
a fast CPU: i's possible for software rendering to be faster.

A well-written application will execute some OpenGL commands and measure
their speed to determine the best way to render something.

-Brian