Re: 3D texture size limitations in mesa/r200?

On Jan 4, 2008 11:52 AM, Roland Scheidegger <[email protected]>
wrote:

> R. Aditya Kadambi wrote:
> > Hi;
> >
> > I am trying do hardware accelerated volume rendering with 3D textures
> > using a scenegraph called OpenRM(www.openrm.org
> > <http://www.openrm.org/>). The program is called vrend which uses 3D
> > textures
> > to HW render 3D raw data.
> >
> > I am using ATI X9250 (R200) card. I am trying to render two sets of raw
> > data. The smaller one which is 64x64x64 is successfully rendered with 3D
> > textures with r200 driver. The bigger volume which is 256x64x256 only
> > appears to be rendered in "half" along the z axis. The other half
> > appears as garbage.
> >
> > I put in a call for 3D texture size and it comes as 256 (which probably
> > means I can render a 256x256x256 cube??).
> >
> > I was able to successfully Software render it on Mesa. It renders fine.
> > Furthermore, it is rendered fine with the ATI proprietary driver (V
> > 8.28.8) (surprise! surprise!).
> >
> > This makes me suspect the r200 driver. Is there an inherent limitation
> > or a bug or a missing feature in the driver (r200/mesa) which might
> > cause this. Is there any way for me to compile mesa with debug flags to
> > test this? Or is there a bug in the lower level ati driver?
> This should work. The hw seems to have a limit for the depth of a
> texture of 256 (not sure why ati's driver can support more, maybe the
> limit is actually not what's stated...), the other directions might
> potentially work even up to 2048 (or not, maybe it would exceed the
> internal range of the address calculation somewhere).
> I suspect what's happening is that the driver exceeds the blitter limits
> somewhere when uploading textures, since 3d textures are submitted to
> the hw as huge 2d textures (well the width is normal but the height is
> huge). There were similar problems in the past with large, mipmapped 2d
> textures (the fix for that was 554e5a2eaf4b681b5c43b6aeb66f100a66da4a42).
>
> Roland

How do I debug this in the r200 driver? Any specific debug flags I can
compile with and report back?

-Aditya

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