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GabrielZ
09-05-2011, 01:15 AM
The documentation for ARB_transform_feedback3 (http://www.opengl.org/registry/specs/ARB/transform_feedback3.txt) states the following limitation:

"in the initial implementation, the geometry shader output topology must be POINTS if multiple streams are used"

Is that limitation still there?
Could anybody give an informed guesstimate when that limitation will be lifted?

Best regards,
Gabriel.

aqnuep
09-05-2011, 03:52 AM
On AMD hardware you can use AMD_transform_feedback3_lines_triangles (http://www.opengl.org/registry/specs/AMD/transform_feedback3_lines_triangles.txt), however NVIDIA hardware does not support it.

If you want to emit triangles to the rasterizer and you cannot stick to AMD hardware then you'll need to render the geometry twice, once for the rasterizer and once for transform feedback.

GabrielZ
09-06-2011, 08:18 AM
Ah, that is very good to know! Thanks a lot for the hint!

For the moment, AMD hardware is fine.
I presume that NVidia will follow, don't you think?

Alfonse Reinheart
09-06-2011, 12:45 PM
If NVIDIA were going to follow (without a hardware upgrade), then ARB_transform_feedback3 wouldn't have that restriction to begin with.

You can generally assume that core extensions are the shared subset of hardware functionality. So if AMD had to make an extension to get around an obvious spec deficiency, there's a good chance that NVIDIA hardware simply can't do it.