Welchen Renderer verwendest du? Was für ein Objekt?
Aus der User Reference:
You can apply a displacement map directly to the following kinds of objects:
Bezier patches
Editable meshes
Editable polymeshes
NURBS surfaces
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 (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.