Render to texture

OpenGL OpenGL: Advanced Coding
1

I wonder if there is a function that would enable someone to take a screen shot while scaling to the destination buffer size.

I meen I would like to have a function that copy the frame buffer data to a texture while scaling to the texture dimensions

The only solution I found is to set up a buffer with the screen dimensions, read back the pixels, scale , and write back to a texture using glTexSubImage2D. The overall process is pretty slow.

Thx for any help
Guard][an

2

Originally posted by Guardian:
I wonder if there is a function that would enable someone to take a screen shot while scaling to the destination buffer size.

Well, you could certainly re-draw the scene at the smaller size in the back buffer then copy it to a texture 1:1.

[This message has been edited by Damon (edited 02-17-2002).]

3

Hi

perhaps you should look at the WGL_ARB_pbuffer extension. There you can create an offscreen buffer with e.g. 100x100 size and render to it as normal. THen you can use glCopyTeximag2d to copy it to a texture.
See also nvidas openglsdk/effectsbrowser

Bye
ScottManDeath

4

Hum, I can’t render the scene twice, because the part of code which needs the screenshot in the texture knows nothing about how the previous stuff was drawn.

I would be nice to have this scaling in hardware
Guard][an

5

You could just call the function that renders the scene twice, just like with, say, dynamic cube maps. Like so:

set render size to 128x128

render scene without needing the texture

glCopyTexSubImage

set render size 800x600 (or whatever)

render scene from scratch; when getting to the part where you need the small texture, use it.

6

Originally posted by Guardian:
[b]I wonder if there is a function that would enable someone to take a screen shot while scaling to the destination buffer size.

I meen I would like to have a function that copy the frame buffer data to a texture while scaling to the texture dimensions

The only solution I found is to set up a buffer with the screen dimensions, read back the pixels, scale , and write back to a texture using glTexSubImage2D. The overall process is pretty slow.

Thx for any help
Guard][an[/b]

You could render to an off screen buffer (pbuffer) and then bind this buffer as a texture. Here’s a white paper describing this technique:
http://www.ati.com/na/pages/resource_centre/dev_rel/ATIpbuffer.pdf

7

chrisATI

Are you awared of such possible bugs in your ICD:

  1. I have to bind pbuffer to texture every time I want to bind texture. I believe it have to be done just once.
  2. When I try to use render_texture extension or simply copy image from pbuffer (via glCopyTexSubImage), and after that I use this texture with envmap_bumpmap extension, machine hangs. This happens only on R200, on R100 everything is ok.