Autodesk 12812-051462-9011 User Guide 3 - Page 234

■ NURBS surfaces on page 2237 For other kinds of geometry such as primitives, extended primitives, compound objects, and so on, you can't apply displacement mapping directly. To use displacement mapping with these kinds of objects, apply a Disp Approx on page 1340 (Displacement Approximation) modifier. This makes the object's surface displaceable. Disp Approx works with any kind of object that you can convert to an editable mesh. Displacement mapping isn't visible in viewports unless you apply a modifier to make it so. ■ For NURBS surfaces, you can make displacement mapping visible in viewports and editable as a mesh object by using the Displace NURBS on page 1117 world space modifier. ■ For editable meshes and objects with Disp Approx applied to them, use the Displace Mesh on page 1115 modifier to obtain the same effect. NOTE If you apply a UVW Map on page 1931 modifier to the surface, all maps obtain their coordinates from the modifier except for the displacement map, which always obtains its coordinates from the original surface or the Disp Approx modifier. Under certain circumstances, such as when the underlying mesh is fairly simple, displacement mapping of an editable mesh can cause problems because of the way the underlying mesh is tessellated. (These problems don't occur when you apply displacement mapping to a NURBS surface.) When this happens, smoothing does not work properly and you can see the underlying wireframe mesh in the surface itself. To correct this problem, use these techniques: ■ Avoid applying displacement mapping to large areas of a single color. Map the diffuse color and use a small amount of variation, such as slight amount of noise, in the map you use for the diffuse color. ■ Add a small amount of noise to the map you use for displacement. This can complicate the tessellation enough to ease the problem. ■ Add detail to the mesh. The more initial faces, and the smoother the mesh curvature, the more even the displacement mapping will be. Standard Material | 5489