[Sidefx-houdini-list] VEX shaders and particles

Jeff Higgins jeffrey.higgins at gmail.com
Sun Nov 18 12:25:05 EST 2007


a sprite is a camera-facing plane, so the s,t coordinates will be the
texture coordinates
for each point on each plane

so a particle point

.

at render time will be a sprite
3 --- 2
|      |
0 --- 1

where 0,1,2,3 represent the a simple plane with s,t mapping to
0: (s,t) = (0,0)
1: (s,t) = (1,0)
2: (s,t) = (1,1)
3: (s,t) = (0,1)

when the renderer dices up the plane into micropolygons
then this attribute will be interpolated between 0 and 1 for s and t

probably more information then i needed to add, but hopefully it explains it
enough!

most likely you'll need s,t and if you're trying to generated a procedural
pattern or for texture look ups when rendering your sprites.

cheers!

jeff


On Nov 18, 2007 5:08 PM, Oodini <svdbg at free.fr> wrote:

> Oodini a écrit :
>
> > When you apply a VEX shader to a particle system, what do the s ant t
> > parameters of the "Global Variables" VOP represent exactly ??
>
> I forgot an important think : I placed a sprite on each particle...
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