If you have the professional version of Terragen, you can create a displacement map from an object:
Original geometry:
[attachimg=1]
Object shape displaced from terrain
[attachimg=2]
You can render the geo with an orthographic camera and output the
tgSurfPos (surface position) as a Render Element. The green channel of the tgSurfPos is the vertical position, equivalent to displacement values (render as 32bit EXR). You can then pipe this onto your surface using a Displacement shader and a Green to Scalar to extract the vertical channel. The downside is that it won't work with complex geometry like the teapot in the previous example (that would need vector displacement) but for simple geo that has no undercuts it works quite well.
When you render the render element for the tgSurfPos file, make sure the object is on a flat undisplaced terrain or you'll get that baked into the map.
example TG scene:
https://www.dropbox.com/s/nnkgl0m204y1f6m/object_displacement.zip?dl=0I did try a render with the teapot with UVs and the transform shader, but I get displacement cracks where the UV shells are:
[attachimg=3]