Hi,
Just wanted to share my experience and the settings that works out the best for me. I checked out Opeth’s a nice post with detailed explanations, but some of his advices diddn’t work out for me (e.g. the smoothing part). That’s why my following suggestions differ significantly from his. Try both and decide yourself.
Zbrush
- Create Displacement WITH Smooth UV, because we will be using TurboSmooth in max. Use Adaptive if needed. This doesn’t seem to impact the “correctness” of the displacement, which has been my main concern, but “only” the quality.
- Note the Alpha Depth Factor on the bottom of the Alpha palette. This value will be used later as the displacement height. In my example it’s 1.5316.
- Export the displacement map, I’m using the DE and the setting of DE-HBEK-EAEAEA-R32. Yes this is a 16bit map, as mental ray is giving me a hard time reading 32bit maps on my aged computer. But as far as I can see, the depth influences the smoothness and quality of your displacement, but not whether it is correctly interpreted by mental ray.
- Export basemesh on lvl 1 (or whatever you used for displacement generation) and make sure Mrg is ON so the UVs can be smoothed with TurboSmooth without fixing them in max. Scale should be 1.
MAX
- Import your basemesh, include smoothing groups and texture coordinates, of course.
- Apply TurboSmooth. I’m applying a higher iteration for render time, at least 2.
- Material settings: under mental ray connection, activate Displacement and use Height Map Displacement. 3D Displacement works as well but I tend to have less predictable results with it.
- Bitmap settings: Using Height Map, you don’t need to offset the RGB in the Bitmap’s output (as opposed to 3D Displacement). I minimize the Blur to 0.01 just to be sure.
- Height Map Displacement settings: Height should be the Alpha Depth Factor, minimum is negative and maximum is positive. E.g. -1.532cm and 1.532cm, respectively.
- mental ray/ Displacement (global settings): Edge length defaults at 1 pixel which is good. Opeth suggested 0.5 to anti-alias it further.
Max Displace just has to be higher than your highest Alpha Depth Factor.
Smoothing doesn’t seem to have an impact, contrary to what the help file says.
Max Subdiv doesn’t show the levels but the pulldown corresponds to them nevertheless. (256 = subdivide 4 times). The important thing here is that you have to count the “levels” here and the TurboSmooth iterations together, and they should add up to your subdivision levels in Zbrush.
I’m using TurboSmooth to subdivide the geometry because mental ray alone gives me crappy/buggy results. I really would have liked if all displacement subdivision was done at render-time, but it doesn’t work out for me.
Also if you have different subdiv levels on different meshes, you can control each with individual TurboSmooth iterations. For instance, I’m having 7 subdiv levels for my sculpted hair in Z, in Max the hair obj has 3 levels of TurboSmooth iterations, plus Max Div 256 (“level 4”) in mr displacement, the result is very close to the original.
I might post images later, but for now I have to move on, this has already cost me too much time. Unbelievable that there’s no readily available official and/or reliable solution for this workflow, considering the popularity of both program and Zbrush’s primary use.
Hope this helps. I’m interested in knowing if my settings work out for you. Good luck and have fun.