For the power that has been given to me, I declare Zbrush and Vray’s vector displacement MARRIED FOR THE ETERNITY.
And you’re all invited. I bring you peace and love for everyone. IT WORKS. Olé.
Vlado, Zbrush is not using odd UvMap!!
Zbrush haves a “BUG” like a house. It not accept a UV Map in the range (0,0) (1,1) (I’m talking Uv map space). Zbrush accepts a range from (0.0…1, 0.0…1) to (0.9999, 0,9999). I bet in the Zbrush Uv Map range code someone has written a range >0 and <1, in place of >=0 and <=1.
So, every UvMap of yours low poly models should be a little bit shrunken, a litte bit scaled down, for Zbrush do maps correctly.
In Zbrush preferences>ImportExport>Vector Displacement Mapping settings, the valors we was looking for are:
FlipAndSwitch = 3 (Vector displacement Absolute in Vray)
Tangent FlipAndSwitch = 1 (Vector Displacement in Vray)
The other options (crease, tangent eval mode…) as default.
With this settings and the detail of UvMap a little scaled down, at last, Zbrush will produce correct vector displacement maps. BUT, for start, don’t create a “tangent” vector displacement, so leave “vd Tangent” unchecked for do it in World (absolute) type.
Please, don’t confuse ourselves, remember, if you subdivide your low poly with “suv” pressed in Tool>Geometry palette, when you create Vector Displacements, leave checked “vd SUV”, and if you gonna smooth your low poly normals on Maya, then leave checked “vd SNormals” too.
Now, in Vray for Maya, if you’ve created a WORLD vector displacement mapping (In Zbrush you’ve leave uncheck “vd Tangent” when you create Vector Displacement Map), just choose in your Vray Displacement Control Extra Attributes:
Displacement Type: Vector Displacement Absolute. All the rest, leave it as default. And that’s all, it should be working perfectly.
But, people of Chaosgroup, let me dare myself to say you’ve a BUG too. Let’s see it.
Create a plane (gonna be easy for see it) in Maya, scale down a little bit the uvs for it doesn’t touch UvMap border’s space, you know, the Zbrush bug. Export it to Zbrush and subdivide it and sculpt it a little bit (you choose if subdivide it with “smt” activated, for smooth uvs or not).
Create another Vector Displacement Map, but this time, not the World (Absolute) one, this time, the TANGENT one (checking “vd Tangent” in Zbrush this time). (Remember the correct flipxyz setting number is 1 for the tangent vector displacements maps). If you’ve choosen before subdivide with “smt” uvs, then now you’ll need activate “vd SUV” before create the vector displacement map.
Now go to Maya, and prepare all for make a render, but this time with Displacement Type as “Vector Displacement” (not the absolute one).
Load in Diffuse channel a photo (any not pattern image, different in all places, like a photo, or a cool wallpaper). (This will help you to see).
Set “Displacement Amount” to 0. (I want you see it from 0).
Put 4 spheres (or cones, or cubes) at the four corners of the plane, activate subdivision & displacement for Rt and launch VrayRt.
Ok, with Rt working, up Displacement Amount to 0.2. You now should be viewing a “almost” correct displacement, but plane, in place of “grow” in heigh, is being “eaten”, cut in XZ plane, while grows in Y (I’m talking in Maya world coordinates). If you up it at 0.3, you can see more area is dissapeared, but more augmentation in Y.
I’ve tested 48 possible combinations, number 18 appears good enough, but the correct one is 1, and all 48 are “eaten” by Vray Vector Displacement Mode when raise the “Displacement Amount”.
Change in the Displacement Node from “Floating Point Absolute” to “Signed Encoding” doesn’t changes anything.
I’ll edit the post for leave a link with some stuff, but you can test any model with this explication.
Have been 2 or 3 days long and right now, I don’t know if I’m forgetting something, so, please, if appears I miss something, ask about.
Here you have some stuff to start to play (Here you’ll find the “Vector Displacement bug” I mentioned with a plane and four spheres to understand it, it includes a color map to you to see):
http://www.mediafire.com/?3ldge4fidorxezv
Please, if all is correct and works, remember update the Vray for Maya help!!.
Eeerr.. ok, its not a bug! http://www.zbrushcentral.com/showthread.php?175879-BUG-with-Zbrush-UV-map&p=1002668#post1002668
Ok, I’m editing an hour more or less after the first post. I’m shaking of laughter. What!? Anyone try nothing different than mushrooms and ears sculpted over planes!?. It always worked!!!. It appears incredible…