You can displacement map all mental ray for Maya geometry types (polygon meshes, free-form objects (NURBS curves/surfaces), and subdivision surfaces.
mental ray uses an adaptive tesselation approach to better fit the details of the displacement map. The initial tesselation (for NURBS: after surface approximation) is further subdivided to fit secondary criteria, controlled by the displace approximation settings. By default, mental ray for Maya creates appropriate settings that lead to curvature dependent subdivision of the triangles, one form of feature-based displacement mapping. You can change these settings by creating or selecting a custom displace approximation node in the Approximation Editor (Window > Rendering Editors > mental ray > Approximation Editor).
It’s important to specify an accurate Max Displace value for the objects being displaced. The typical approach is to derive this value from Maya’s Bounding Box Scale, but this is not suitable in all cases. As an alternative, you can use the Max Displace setting (Render Settings: mental ray tabs, Options tab, mental ray Overrides > Displacement section) to control shape nodes. To determine the right value, set the Max Displace to 0, and adjust it according to the messages in the Output window.
