PDA

View Full Version : Extension clarification



Nychold
06-30-2004, 08:04 PM
I just recently picked up a Radeon 9800, and took a look at the supported OpenGL extensions. Since my last card was a GeForce 2, there's quite a few new features in there, most of which I recognize from other posters here. But, there's one which I guess I've never come across in study: GL_ARB_vertex_blend. I know the Radeon 9600+ support full scene antialiasing, but does this extension control that, or is it something else? Also, if it is, can someone point me to an example, or demo of this? Thanks. ^^

CrazyButcher
06-30-2004, 11:49 PM
it allows weighted transform of vertices

like done in skeletal animation, ati should have a demo on their developer site

though the whole extension is not that common anymore, as vertex_program kinda made it outdated.

-NiCo-
06-30-2004, 11:54 PM
You can find the complete specification at:
http://oss.sgi.com/projects/ogl-sample/registry/ARB/vertex_blend.txt

Here's an abstract:


This extension provides the ability to replace the single
modelview transformation with a set of n vertex units. (Where
n is constrained to an implementation defined maximum.) Each
unit has its own modelview transform matrix. For each unit,
there is a current weight associated with the vertex. When
this extension is enabled the vertices are transformed by
the modelview matrices of all of the enabled units. Afterward,
these results are scaled by the weights for the respective
units and then summed to create the eye-space vertex. A
similar procedure is followed for the normals, except they
are transformed by the inverse transpose of the modelview
matrices.
It is mainly used in skeletal animation to achieve smooth transitions between 'keyframes' using a simple weight factor.
It also has other interesting uses, like speeding up stencil shadow volumes etc.

Nico