The Displace modifier acts as a force field to push and reshape an object's geometry. You can apply its variable force directly from the modifier gizmo, or from a bitmapped image.
Displace used to change the surface in the container
There are two basic ways to use the Displace modifier:
The Displace space warp has similar features. It's useful for applying effects to a large number of objects or a particle system.
Displace distributes its force through four different gizmos: Planar, Cylindrical, Spherical, and Shrink Wrap. Gizmos are also used as mapping coordinates for applying bitmaps. Sphere and Shrink Wrap have the same effect when modeling, but differ in the way they map.
The Spherical and Shrink Wrap gizmos begin with a uniform field around them. The Cylinder and Planar gizmos are both directional. Cylinder pushes at right angles to its axis, and Planar pushes at right angles to its surface.
By default, gizmos are centered on the object. However, you can transform any of these shapes and use it directly as a tool to deform the geometry of an object.
Displace is a versatile modifier with many possible applications. Here are some options:
Displace an object:
Depending on the object and the complexity of the bitmap, you might need to use dense geometry to see the effect clearly. Try a test run and, if necessary, add tessellation in the areas of greatest detail.
To apply a bitmap as a displacement map:
After you get the image you want from bitmapped displacement, you can apply an Optimize modifier to reduce the complexity of the geometry while retaining the detail.
Model with the Displace modifier:
Subdivided box deformed with Displace, using the Cylinder gizmo