[Sidefx-houdini-list] Anisotropic work around?

James Rutherford jrutherford at stclaircollege.ca
Mon Feb 20 12:59:06 EST 2006

So it this what Max and Maya are doing with anisotropic on polys???

all the code is on the guys site but its mental ray...can this work with 
VEX...its all greek to me......



*Shader Type:* Texture
*Output:* Color
Used as passthrough shader to compute UV derivatives on the fly.
*Passthrough* 	The shader puts the calculated u and v derivatives into 
state->derivs[0] and state->derivs[1], and then calls whatever shader is 
plugged into the passthrough port. This means that all shaders that are 
to the left of the Deriver get the modified u and v derivates.
*Mode* 	Allows you to either disable the shader (the passthrough will 
still be executed, but the derivatives will not be touched), or to 
choose a north pole or north direction input. North Direction means that 
the input vector points towards the north pole, for all rendered pixels. 
North Pole means that the input vector is a location, and the shader 
will compute the north direction for each pixel on the fly. You can for 
example link the north pole to the location of a null to get the 
possibility to interactively place the north pole.
*North Direction* and *North Pole* 	Two input vectors, the appropriate 
vector will be used depending on the Mode selected.
*Rotation* 	Allows you to rotate the u and v direction vectors around 
the surface normal. This works like the rotation color in the 
Anisotropic shader, but is just a simple scalar. All multiples of one 
are full 360° rotations, 0.5 is 180 degree, etc...

*Render Tree Usage*
The main idea behind this shader is to miracle U and V derivatives onto 
polygon surfaces, so that you can use the Anisotropic shader with them. 
To make this work, just plug the Anisotropic shader into the passthrough 
port, plug the Deriver shader into the Surface port, and enable the shader.

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