How to make a displacement map from existing 3d geometry

Question

In true stackexchange tradition. I am interested to see how people approach generating a good quality displacement map from existing 3D geometry. For completeness, list the qualities that make up a good displacement map. I'm not looking for links to external tutorials, but short descriptions of your methods are welcome.

My current method involves setting up a orthographic camera viewing the geometry, and setting the far and near clipping field to the extents of the geometry. Then render the image and extract the z-buffer by normalizing it so it becomes a grey scale and outputting that as a file from the compositor.

I will elaborate on my method as an answer, if no one offers a more convenient procedure.

Answer 1

The best way I know is to use Baking. You must have your plane (or whatever the low-res object is) UV mapped with a new image assigned to all the faces you want to bake to (select faces in edit mode, select/reselect the image in the Image Editor). Then in the Render settings, at the bottom is the bake panel.

Normalized allows you to specify a maximum distance Selected to Active is important too, enable it to ensure the displacement is baked from all selected objects to the active/last selected object.

Example: (Note that baking doesn't play nice with overlapping geometry - in this example the underneath of the sphere and torus was deleted, and the sphere moved up to ensure it doesn't collide with the torus. Not doing this will produce artifacts.)

Answer 2

One way to solve it is with a gradient texture, it's crude but it works. This also gives you lots control over the output. If you want to separate objects but need to have them appear on the same plane, this works. If you want to blend multiple details, this works (using translucent textures).

View your object from the side, in edit mode hit u and project from view (bounds).

Assign a white-black gradient. Make the object self illuminating.

Render from top. Make the camera orthographic and adjust the scale to fit the object.

This only works for flat renderings. For the height above a sphere (such as mountains on a planet), this does not work, use baking. This solution can work in some conditions, making it an alternative to baking.

Answer 3

The trick here is to make the distance between the near and far clipping plane as short as possible.

• Set the camera to orthographic and render using blender internal, no lights needed, or materials, all we are interested in is the z-pass
• in compositor convert the Z-output to a linear grey scale using normalize and color ramp (altho other ways are possible)
• the short distance between the clipping planes helps bring out more detail. Suzanne is not a great example, you could bring the far clipping plane up to the tip of the ear where it first starts to fold away from view

Folding away from view, so can clip beyond it.

A tilted Suzanne gives more obvious topographic range

That's all there is to it.