The Displace Mesh world-space modifier (World Space) lets you see the effect of Displacement mapping on editable mesh objects and objects with a Disp Approx modifier applied to them. If a displacement map is applied to the object, the mesh shows the effect of the displacement map. Displace Mesh replaces the mesh with its displaced version.
There are two main reasons for using Displace Mesh:
For example, if you use an animated displacement map to create waves on a water surface, you might temporarily apply Displace Mesh to see where the ripples meet the waterline of a boat.
When you use Displace Mesh in this way, usually you delete it once you've obtained the effect you want.
To use the Displace Mesh this way, you apply it to the object that has a displacement map, then apply the Snapshot command from the Tools menu, and choose Mesh as the clone method.
Snapshot creates a permanently displaced mesh. As it does for other kinds of objects, Snapshot also leaves the original, displacement-mapped object in the scene. After applying Snapshot, you can delete the original object, or you can keep it in your scene to use for other purposes.
The rollout for Displace Mesh lets you choose which surface approximation settings are used to produce the mesh.
Subdivides mesh faces to accurately displace the map, using the method and settings you specify in the Subdivision Presets and Subdivision Method group boxes. When turned off, the modifier applies the map by moving vertices in the mesh, the way the Displace modifier does. Default=on.
Affects the seams of displaced mesh objects; also affects texture mapping. When on, 3ds Max splits the mesh into individual faces before displacing them; this helps preserve texture mapping. When off, 3ds Max uses an internal method to assign texture mapping. Default=on.
Subdivision Presets group and Subdivision Method group
The controls in these two group boxes specify how the modifier applies the displacement map when Custom Settings and Subdivision Displacement are both turned on. They are identical to the surface approximation controls for NURBS surfaces.