Clarification on VRayMtl anisotropy

[DeadLift315]

Hi!

I have been creating kitchen props for a scene I am working on and either ran into an issue or am not using this parameter correctly. The information in the v-ray help documentation is very limited on this subject, and I would appreciate any help or solutions with this issue.

From what I can tell anisotropy appears to have some issues with the topology of certain geometry. In particular very thin non primitive geometry, such as the blade of a knife. I did some further tests with primitives and found that simple shapes with out chamfered edges also behaves strangely. to make things even more confusing i found that the geometry for a chamfer box primitive renders differently than a box primitive converted to an editable poly and chamfered using the edit poly tools.

Here are some images of the issues i am running into. Thank you for the help!

[Guest]

Are you using a UVW map for a brushed texture or anything? If so try changing the UV vectors derivation to Map channel in the material. We had a similar issue a while back and that fixed it.

[samuel_bubat]

I also noticed that high anisotropic values (we´re still on vray 2.4) produce visible errors if the mesh resolution is not high enough. Try a subdivide modifier with
very fine settings and see if this helps. Regarding standard primitives. It seems anisotropy can´t handle default mapping coordinates. Apply an UVW Map and it should
render ok.

[^Lele^]

In general, anisotropy, as opposed to round speculars, needs two more directions to stretch the highlight (or one and its calculated orthogonal counterpart).
As such, U and V are ideal.
However, a non-continuous UV will result in non-continuous anisotropic highlight.
The best job you can do for it is to unwrap the mesh' UVs such as there are no visible UV seams in the interested parts.

[DeadLift315]

Thank you all so much!

The Map Channel setting with nice clean UV's is definitely the way to go! Another advantage of this is that it allows you to orient the anisotropy in different directions on the same mesh. So for instance, if there were a element of metal that were brushed in a different direction you could control this by rotating the UV elements associate with that geometry.

Thanks again!