Tutorial 3dsMax -- Disp Approx modifier
The Disp Approx modifier lets you apply Displacement mapping to an object. Disp Approx (short for Displacement Approximation) converts its input object to an editable mesh, so you can use this modifier to add displacement mapping to geometry primitives and any other kind of object that can convert to an editable mesh.
Sometimes completely unknown, the modifiers are very useful during the normal workflow of 3dsMax. These are old videos created with 3dsMax2010 but the modifiers are equal to the latest versions