[osg-users] [Fwd: Mesa and gldirect]

Paul Martz pmartz at skew-matrix.com
Mon Mar 23 13:48:27 PDT 2009

There's a very simple answer to the ATI problem: don't buy ATI. Seriously,
their poor OpenGL support has been well-known for at least seven years, if
not longer. In light of this knowledge, why do people keep buying ATI cards
for OpenGL use? It just doesn't make any sense.

Paul Martz
Skew Matrix Software LLC
+1 303 859 9466

-----Original Message-----
From: osg-users-bounces at lists.openscenegraph.org
[mailto:osg-users-bounces at lists.openscenegraph.org] On Behalf Of
Jean-Sébastien Guay
Sent: Monday, March 23, 2009 2:04 PM
To: OpenSceneGraph Users
Subject: Re: [osg-users] [Fwd: Mesa and gldirect]

Hi Jan,

> Honestly, I think this will be counterproductive. It will only give 
> companies an excuse to neglect OpenGL support further or to drop it 
> completely ("You can use the emulation!"). The latter would be 
> disastrous for all non-Microsoft platforms.

Since the OpenGL over Direct3D layer will only work on Microsoft platforms
for obvious reasons, I don't see how this will affect other platforms at
all. If some developer wants to do 3D on Linux, they have to use OpenGL.

Basically, this is a follow-up to an earlier discussion (a rather long and
heated one as I recall) saying that there were two ways to improve the OSG
experience on Windows platforms or for ATI/AMD hardware, where OpenGL
drivers are pretty bad compared to nVidia:

1. Demand better OpenGL support in drivers (which may be hard and does not
depend on us, i.e. we can ask but we have no control over the result)

2. Create a technological solution, of which an OpenGL over Direct3D layer
is one example.

Of course, it would be much preferable if vendors would, out of their own
volition, improve OpenGL driver quality on Windows. However, since most
games run on Direct3D, there is little incentive for them to do this. In
most markets where OpenGL support is important, the software is already
cross-platform, and thus moving to Linux is less of an issue. 
This means that the situation with OpenGL driver quality on Windows is
likely to get worse as developers who depend on OpenGL move to other
platforms and stop demanding good OpenGL driver quality.

> I fail to see the benefits of such move - why to run OpenGL on top of 
> Direct3D? Is there *any* usable hardware that has only D3D drivers and 
> does not support OpenGL?

Perhaps not, but for most hardware which has Direct3D support, the Direct3D
driver quality is higher than the OpenGL driver quality on Windows (either
in speed, number of serious/show-stopper bugs, etc.). 
There's a big difference between supporting OpenGL and supporting it *well*,
and since there are no enforced conformance tests, vendors can support it
only partly if they want...

Basically, I'm trying to find a way so that OpenGL apps can run well on
Windows, independent of what vendor made the graphics card. Since there is a
large pool of Direct3D applications on Windows, making OpenGL calls go
through Direct3D before getting to the video card driver might be one way of
doing that.

Of course, this is all theoretical, we can't know what the trade-offs are
until we get a prototype running. And in any case, I'm just relaying info I
got, seeing as this discussion was raised before. If the majority of people
don't see the benefit, nothing will come of it and it'll just die, and we'll
just go on as we have in the past.

Jean-Sebastien Guay    jean-sebastien.guay at cm-labs.com
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