Rendering Mudbox vector displacement with V-Ray
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Sculpting the object in Mudbox
Exporting the base object from Mudbox
Exporting the vector displacement map from Mudbox
Rendering the object with V-Ray for Maya
In this example we will render an object with vector displacement map created in Autodesk Mudbox.
There are a few things to keep in mind when painting your object in Mudbox:
Here is an example of an object sculpted in Mudbox:
Go back to the 0-level resolution of the object, select it and export it to an .obj file from File > Export Selection...
Go to Maps > Extract Texture Maps > New operation... and in the following dialog select Vector Displacement Map.
For Target Models select the 0-level resolution of the object; for Source Models select the resolution that you want to bake (typically the highest resolution).
Turn on the Smooth Target Models and Smooth Target UVs options.
Set the desired resolution of the displacement map.
Set the Vector Space to Absolute Tangent - this is important; none of the other modes will work properly.
Select an OpenEXR file as the output vector displacement file.
This is what the final extraction options should look like (click on the image for full resolution):
Click on thebutton to create the vector displacement map.
Here is the Mudbox UV view with the extracted map:
In Maya, import the .obj file with the 0-level resolution mesh for your object.
Select the shape node of the imported object and apply V-Ray subdivision attributes to it. Leave the settings at their default values:
After that, assign a new material to the object (I used a VRayFastSSS2 material with the Milk (skimmed) preset, and assign a displacement shader to it. Create a File texture for the displacement source and point it to the exported .exr vector displacement file. For Maya 2012, leave the map attached to the Displacement slot of the displacement shader, and not to the Vector Displacement one.
With the File node still selected, go to the Attribute Editor, Attributes > VRay > Allow negative shader colors. This will add a V-Ray specific option to the File node, telling V-Ray that negative colors are ok for this textures. Another option would be to enable negative shader colors globally in the V-Ray settings. If you don't set one of these options, V-Ray will clip negative portions from the displacement map and it will produce wrong results.
Select the shape node for the imported object, and in the Attribute Editor, go to Attributes > VRay > Displacement control. This will add a group of attributes to the shape for controlling the displacement. Set the Displacement type to Vector displacement (absolute).
Optionally you can add the Subdivision and displacement quality group of attributes to control the quality of the displacement result.
That should be all - the object is now ready to be rendered: