Render to VBO on 2008 cards
Author
Have things changed since 2006?
http://www.gamedev.net/community/forums/topic.asp?topic_id=434618
I'd like to try an algorithm that requires vertex shader to look up textures, but when searching I keep bumping into info from 2005-2006 saying that ATI requires using render-to-vertex-array extension in a pixel shader instead, while NVidia uses a very picky texture sampler in vertex shaders.
Has any of this changed? is there now a standard (and fast) method to calculate new vertex positions using texture data?
I'm thinking about terrain rendering/displacement mapping, btw.
Edit: I'm running an ATI 9600XT, Should I look into an upgrade?
[Edited by - Madster on August 25, 2008 9:30:27 PM]
All DX10 hardware has VTF, GF6 and newer, and ATI IIRC x2000 series and newer has it. From what I been told it's fast on DX10 hardware now to use VTF... So yes, you need to upgrade, and I would recommend a GF series card.
One form of render-to-vertex-array that can be done on older hardware: render to offscreen memory (e.g. a FBO), then ReadPixels into a PBO. Then bind the same buffer as a VBO.
While this requires copying the data to the buffer, the copy can be performed in-band and without requiring a round trip to the host. Thus it should be very fast.
While this requires copying the data to the buffer, the copy can be performed in-band and without requiring a round trip to the host. Thus it should be very fast.
Author
Thanks, I'll give the PBO technique a try. I remember reading it was very slow, but when I read this it was about modifying texture data trough the CPU, so the transfer was needed.
Author
the in-band part lost me, would I need to do something special for this to be in-band?
I already looked up the functions needed and I got the idea, except for that.
Thanks!
EDIT:
Not far enough apparently :-/ My target hardware changed to OpenGL ES 1.1, and that doesn't seem to have PBOs
It does have FBO if it has the OpenGL ES 1.1 Extension pack (which I'm not quite sure if it's installed by the client or the driver).
anyway, seems I could do the copy anyway with readpixels, but I'm not sure how fast it would be.
I already looked up the functions needed and I got the idea, except for that.
Thanks!
EDIT:
Quote:How far back does PBO support go for hardware?
Not far enough apparently :-/ My target hardware changed to OpenGL ES 1.1, and that doesn't seem to have PBOs
It does have FBO if it has the OpenGL ES 1.1 Extension pack (which I'm not quite sure if it's installed by the client or the driver).
anyway, seems I could do the copy anyway with readpixels, but I'm not sure how fast it would be.
In-band just means it executes serially with other commands in the command stream and therefore requires no sync/stall. In plain English: its fast.
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