By default, Maya uses feature-based displacement mapping to attain high quality displacement mapping with the lowest impact on rendering resources. Displacement features are parts of the texture used as the displacement map that provide the information for the height variations (depressions or elevations).
This technique detects the density of the features in the displacement texture (that is, the more detailed areas) and adds triangles to the tessellation only where needed, keeping the triangle count to a minimum.
When using this technique, the tessellation attributes do not have to be set high, just high enough to capture the surface shape.
With non-feature-based displacement the software renderer does not add vertices to the geometry being displaced. As a result, many of the features in the displacement map may be lost if there are not enough vertices in the model.
Maya tries to alleviate the potential loss by bump mapping (in addition to displacement mapping) the displacement map to perturb the normals to create the features where there are not enough vertices. In this case, the bump map’s Bump Filter and Bump Filter Offset attributes (if they have them) are automatically adjusted for optimal results.
If the material cannot be bump mapped (for example, Layered Shaders cannot be bump mapped), the texture is instead connected as a displacement texture and no bump mapping occurs. You should connect this texture as a bump map where it makes sense. For example, use the displacement texture as a bump map on the various materials connected to the Layered Shader. Attach the bump node to all Normal Camera attributes in the shading network you have just displacement mapped. Also, if you drag a texture onto a displacement node manually within Hypershade instead of dragging from Hypershade onto the Displacement Attributes area in the Attribute Editor, no bump map is connected, and the displacement may not look right.
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