Vector Displacements

Regular Displacement mapping

With traditional displacement maps, as demonstrated HERE and HERE, the surface point is moved along the surface normal. This can be driven by a procedurally generated pattern or a displacement map from a paint or sculpting application. The displacement map is a greyscale image which specifies how far (by the grey values) each surface point should be displaced.

Whilst this can bring highly detailed displacement, a model which reflects the general surface shape must be used (i.e. an intricate head model could not be displaced from a flat plane object, with a traditional displacement map) Similarly the geometry would need to have any overhanging or undercutting areas explicitly modeled prior to displacement being applied.

Vector Displacement mapping

Vector maps are RGB images which describe where a point on a surface should be moved in world or object (shader) space.

Using a high bit depth EXR file containing 3D vectors, highly detailed displacements can be applied to a subdivisional surface.
Because these are 3D vectors, rather than following a fixed surface normal, they can move in any direction, and even overlap each other.


Here you can see there is overhanging displacement, and the vectors are able to overlap.

Example Application

Below you can see a very simple example of sculpted modeling to create overhanging geometry.

Mudbox screenshot

This was a basic 'grab' operation within mudbox on a regular polygon plane.

Vector Displacement Map (exr file)

Next a vector map was extracted from mudbox in the form of a 32bit EXR file:

RenderMan Render & SLIM shading network

Finally this was loaded into a simple texture vector shader in SLIM, and connected into a displacement function and attached to the flat polygon plane in Maya. you can see there is identical displacement to the mudbox screenshot.

See Also

Fundamentals - Per Face Textures - Ptex

HowTos - Ptex Textures, Baking Ptex files, Displacement 1, Displacement 2