so here’s the bottom line of the issue and how I worked around it based on this demo object.
The only option is baking to a Normal Map, which works great. The (unsolved) problem is, that I haven’t found a way to convert the Normal Map into a Height Map without issues. Unfortunately the created Normal Map cannot be used as a direct input into the Displacement Node for Micro-Displacement (not a Blender issue - doesn’t work in 3DS Max either).
Blender Render (Bake from Multires)
Not really usable for my purposes. For one the faces of the low level polygons are visible in the baked Displacement Map. Unlike when baking the Normal Map in Cycles, I have to reduce the level of the Preview value in the Multi Resolution modifier to 0 for the Displacement Map to show. On top of that, there are weird halos around the sculpted parts.
Blender Render (Working Option)
The only way that I got it to work is like this. I duplicated the sculpted sphere, deleted the Multi Resolution modifier and applied a new one with the same amount of levels, but no sculpting. Then I selected both spheres (having the unsculpted one as the active one) and baked the Displacement Map with the “Bake from Multires” option OFF and “Selected to Active” ON. That’s the only way I got it to work so far.
Here is the created Displacement Map:
What would be great:
With the powerful Micro Displacement in development, I wish I had the option to bake the sculpted changes of a Multi Resolution modifier into a Displacement Map directly from the Bake section. Another option would be, to have some filter node that would convert a Normal Map into a Displacement Map right before I plug it into the Displacement Node. With one of these two options available, the workflow from highres models to lowres models with Micro Displacement would be nice and fluid.
Thanks for all your help, guys.