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Any way Render to VBO directly?


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#1 FireInDark   Members   -  Reputation: 148

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Posted 17 July 2012 - 11:58 PM

OK。I know it is possiable to "Render to Texture " or "Render to PBO" and the throw the data to VBO..
But some topics on web told that maybe Render to VBO is the best way ..
Any one can tell how to do with it ?

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#2 Hodgman   Moderators   -  Reputation: 27908

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Posted 18 July 2012 - 12:47 AM

I'm not the most experienced with this feature, but from what I know:
* You'll find some information by searching for "R2VB" (render to vertex buffer), but AFAIK, R2VB is only possible on certain, old (DX9/GL2?), AMD GPUs.
* On DX10(GL3?) GPUs, you should be able to tell the vertex shader to "stream out" (aka "transform feedback") the transformed vertices to a VBO, instead of rasterising them as triangles/primitives.
* On modern GPUs (DX11/GL4?) there might be a way to render to a texture, but then bind that texture resource as if it were a VBO (i.e. the same GPU memory allocation can be bound as a writeable texel buffer and as a readable vertex buffer), much like R2VB does.

Edited by Hodgman, 18 July 2012 - 12:53 AM.


#3 Koehler   Members   -  Reputation: 228

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Posted 19 July 2012 - 09:11 AM

You'll need to look up a feature called "Transform Feedback" in OpenGL. You can disable polygon rasterization and have the output of a vertex shader stored directly in a VBO. This feature was enabled at least as early as 3.3

Edited by Koehler, 19 July 2012 - 09:14 AM.


#4 japro   Members   -  Reputation: 887

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Posted 19 July 2012 - 09:15 AM

I have a transform feedback example in my examples: https://github.com/progschj/OpenGL-Examples/blob/master/09transform_feedback.cpp

#5 FireInDark   Members   -  Reputation: 148

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Posted 20 July 2012 - 01:45 AM

Sorry for saying thanks so late..
Thanks to all of you ,I will try as you've said ..

I will show the right when it's OK.




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