Renderman: adjust direction of anisotropy

materials
shading
(Mithrandir) #1

Hi,

I wanted to know if anyone knows how to adjust the direction of anisotropy, on materials like metal, ect…

When i mean direction, i want to give a circular shape to the anisotropy, so it looks like a brushed metal.

Thanks a lot!!

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#2

PxrTangentField is your friend.


ie. Vector map

Rotation map

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(Mithrandir) #3

It works, thanks a lot.

Where could i found other vectors? like juste a circle, or a line, ect…?

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#4

You search for gradients, vector maps… or make your own. Goes for all engines (VRay, Arnold, Cycles, Unity, Unreal…) Tools you can use are Substance Designer, PS, GIMP, InkScape, FilterForge… :wink:

Here’s another quickie


made with

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(Mithrandir) #5

Thanks a lot!

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(CarlG) #6

What is it you’re trying to create? Have a look at this image:


Ignore the glass error, my own stupid mismatching IOR mistake. For the nuts:
The 6 faces - standard glossy, as the hexagonal extrusion doesn’t leave a streaking pattern.
Top and bottom faces - aniso (straight UV based, fixed rotation) from lathing process.
Threads - aniso (straight UV based, offset rotation). Threads are microdisplaced cylinder, and the thread pitch angle would cause the aniso to be rotated slightly.
Markings - standard glossy, but doesn’t matter.

It is very beneficial to use multiple UV’s for multiple purposes. I don’t know Renderman, but when I can I use quads only where UV only define direction - scale, density and even overlapping doesn’t matter.

The shader setup is too complex to post here or even understand (some calculated masks as well). I’ll see if I can make a proper teapot.

Edit:
Attached is a simplified use of UV based tangents, on a teapot. Anisotropic_Teapot.blend (1.3 MB)
Uses a seamless noise over U to drive a supertiny variation of rotation angle for the regular stainless version which is rough enough where the grooves would show. You may want to drive roughness or color instead.
The high polish long tail only uses the tangent, as it’s highly enough polished to have almost no roughness at all but still provides very long streaks of light (must use Bechman distribution).
Last is just a standard mirror like polish using glossy, for comparison.

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