Anisiotropic shader on polys - very strange result

[srvargas]

Hi guys.
I have quite a strange issue with anisotropic shaders on a polygon object. The result is a two-color, cell-like rendering with just two colors (black and white). If I aplly the anisotropic on a NURBS object it renders just fine...
Any ideas???

[atyss]

Simple: the anisotropic shader works only on nurbs objects.

Salutations - Cheers
Bernard Lebel

[srvargas]

Are u sure Atyss?
Because I just applied the Anisotropic UV shading preset and it renders sort of fine - just that this preset doesn't have the options of the standard Anisotropic material.
And still - how is it possible for it not to work on poly objects?

[atyss]

Because the specular need UV information that only nurbs can provide :-/
I'll check that Anisotropic UV thing asap.

Salutations - Cheers
Bernard Lebel

[srvargas]

Problem Solved...
In the render tree I took a Color2Scalar node and plugged it into Scalar2Integer, which in turn went to surfderiv_mode input of the anisotropic material. Now shading appears perfectly. I have no idea why, though...If anyone can explain to me, plz...
Happy Holidays

[atyss]

Nice trick!
How did you find that?

Salutations - Cheers
Bernard Lebel

[srvargas]

By chance. I was comparing the anisotropic material and anisotropic uv shading presets and noticed that the uv material has vector inputs for UV generation. Then I started to plug in different conversion nodes to the surface derivation node. Then refreshed the region and it appered as it should be...
But still I cannot figure out why it works - it will be very useful to understand that...Anyway - maybe someone at xsibase may know - you can ask them...
p.s. there is one more strange thing - if you save that whole tree as a preset and apply it on a new object/scene - it doesn't work, even though all the nodes are in the render tree. You have to construct it manually for every single time/object you use it for...

[devdoka]

It works because you generated UV coordinates and not a projection. However, even this is just an illusion. Once you start to re-orient your object or modify the UV coordinates, the illusion of correct Anisotropic shading will probably be lost.

Matt

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Matt Lind
Animator / Technical Director
Softimage certified instructor:
Softimage|3D
Softimage|XSI
speye_21@hotmail.com