[Sidefx-houdini-list] About sprite shader for particle

Andrew D Lyons tstexture at gmail.com
Sat May 22 23:57:47 EDT 2010


Hi Chuong,

If you select the sprite shader and hit the enter key you will see that
inside that SHOP node is a VOPnet that defines the shader. In the shader you
will see inputs for the point color amongst other things. You can in fact
pass in any arbitrary point attribute and use it to modify the shader. For
instance, you can pass in a normal vector to use for shading purposes so as
to override the implicit N vector created by the sprite procedural (you are
correct) which always points at the camera.

Hope that helps.

Cheers


On 22 May 2010 14:38, chuong nguyen vien <chuong_nguyenvien at yahoo.com>wrote:

> Hi,
>
> Houdini already has a sprite shader and a sprite sop. In order to get a
> better understand how it works, I am trying to make a sprite shader from
> scratch. However, i don't know for sure about the way it really works. The
> sprite shader in houdini contains two node, one is the surface shader and
> the other is vm_geo_sprite which i guess is a geometry shader. Here is what
> i get confused:
>
> -When we assign the sprite shader to a particle, how does it take into
> account the color of each particle i set with a color node ? What is the
> relation between them (the color node and the shader) ?
>
> My guess it that, in the vm_geo_sprite node, when we put Cd in the
> attribute, so the vm_geo_sprite will know about the color of the particle
> (but internally, how  does it know ? Or exactly can we make a custom
> vm_geo_sprite node ?).
> Then, the vm_geo_sprite node will override the color of the surface shader.
> But if works like that, then the surface shader is only used for determine
> other characteristic of the particle.
>
> I will very appreciate for every hint about it :)
>
> Chuong
>
>
>
>
>
>
>
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Andrew D Lyons | Digital Artist | http://www.tstex.com
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