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View Full Version : Tessellation Unit on Radeon 5k and OpenGL?



Mars_999
12-29-2009, 08:14 PM
How can one make use of the tessellation programmable unit on the Radeon 5k series cards? Or is this not possible yet?

If so, the way its done on ATI cards, will Nvidia follow suit and do it in the vertex shader? Or is this going to be done in some other shader.
Thanks

Alfonse Reinheart
12-29-2009, 08:23 PM
Look at how it's done in Direct3D 11. That's likely how it will be done in OpenGL.

Dark Photon
12-30-2009, 09:31 AM
How can one make use of the tessellation programmable unit on the Radeon 5k series cards?
Presumably, with this OpenGL extension:
* AMD_vertex_shader_tessellator (http://www.opengl.org/registry/specs/AMD/vertex_shader_tessellator.txt)

More on this here (http://developer.amd.com/GPU/WGSDK/Pages/default.aspx). This is probably the legacy tessellator stuff they've had in their hardware for a while, not the new DX11-style tessellator stuff. But hopefully an ATI guru will chime in here.

For high-level details of what's coming for the OpenGL Shader Model 5 functionality, see this:

* OpenGL: The Train Has Left the Station (NVidia GPU Tech Conference, 2009 (http://www.nvidia.com/content/GTC/videos/GTC09-1407.flv))

Skip to 1:06:04 for SM5 in general, or 1:10:20 for the tessellation stuff in particular. Hopefully EXT/ARB/core support (and the NVidia hardware) will be out before/at GDC next year. Right now, it's ATI-only, so just use their extension.


If so, the way its done on ATI cards, will Nvidia follow suit and do it in the vertex shader? Or is this going to be done in some other shader.
Huh? In DX11, it's new shaders: hull and domain, after vertex before geometry sandwiching a new fixed-function tessellator gizmo. Don't think it'd make sense for the model to be different in OpenGL. See that video I pointed you to. NVidia is calling them the "Control" shader and the "Evaluation" shader, sandwiching the "Primitive Generator".

Mars_999
12-30-2009, 07:46 PM
Reason I said VS is where they dumped the tessellation code at, is someone on the net said that is where that extension was doing its processing...