To Create a Displacement Map from Existing Geometry

Set up a Top view that encompasses just the required geometry.
Re-size the view so that it is square.
Use the Set Display Depth tool to define the near and far clipping planes as the top and bottom of the geometry respectively.
Turn on Clip Back and Clip Front in the View Attributes.
Open the Render Setup Manager dialog and, in the Settings tab, set Render Output to Depth.
Note: If the geometry has prominent curved surfaces, you should use a very fine Stroke Tolerance value.
Start the Luxology rendering.
When the rendering is complete, save the image to a lossless format to avoid compression noise.