Felix,

Say yourself some time and frustration and don't go down the heightmap greyscale road. The bottom line to get the results your looking for you will not get them from 2d graphics. Trust me I tried and tried..lol. I have always been an avid woodworker and tool whore, I sears one day and saw a demo for Carvewright..I was like hmm 2k ish...I can import a photo and carve it...damn I was thinking of all the cool stuff I could add to my work. Needless to say it never worked out that way. Carvewright has a propiatary file system and they have made it so anyone could do cnc...no gcode, no tool paths..just import a photo and carve away. I was completely disappointed with the results. They looked like crap as carvings go. None of the flow and contours would be right either up when was suppose to be down or vice versus. At the time in 08 I never touched a 3d program.

I became the king of photo manipulation..lol you name the program to make a photo a depthmap I tried it and wasted a lot of money on some looking for the holy grail of depthmaps. It was such a waste of time. The guys in the CW community are the kings of depthmap to cnc pattern. But the results are never that good. Some have produced some good patterns with photoshop gimp etc...but again not that good and the time involved bizzare. One of the first programs I boughtt was zbrush for the EXACT workflow your mentioning - depthmap to model to clean up/sculpt in zbrush. Never worked good. Faces for example..the people always looked like aliens with bugged out eyes, noses going inwards etc. I tried inverting etc, gaussian blurs, changing the colors of the greyscale image...it was almost impossible to clean up in zbrush.

Finally I got talking with this guy in the CW community and he was like if you want good results learn how to model with polygons. Here is site for the guitars he makes with the cw http://liquidguitars.com/ seeing his work..I knew he was right. CW came out with an .stl importer and I started making some simple stuff and was very nice and clean..contour etc EXACTLY how I wanted them. The guy who makes the guitars uses lightwave alone..he has been modeling since the 90's for a living. He also tole me avoid artscam as he calls it and aspire..he was like learn how to model and you can do anything you want in cnc.

I took his advice and started with MOI..he didn't like nurbs but hey I love this program...Then it was time to learn quads..Trust me I know what your saying about the learning curve..LOL bigtime..but you will never regret the time spent for cnc models. I look back and go man if I just nutted it down with modelling and left the photo's alone I would be that much further along..lol and a few more bucks in my pocket.

The way I do stuff today is whatever I want to make I try to think which of the two programs to start with..Moi or silo..meaning which peices are going to be faster and easier in produce the desired result. I make the peices in Moi and Silo then generally import them into zbrush and asseble the model there. I don't care about the high polycount as most cnc models have a high poly count. Export obj and then convert to .stl and carve away.

I still use photo's for reference images or a "texture"..I use zbrush lightbox alot for adding texture. I still suck at human faces but I am practicing..attached is one I am trying to do of Jimi Hendrix. I made the frame in Moi, blocked the head out in silo..brought it all into zbrush and compiled to one there...now have to sculpt to get better..lot of worked left on it. I am using a photo laid out in light box to add some detail. The other tricky part I am trying to keep this as low relief...75 in depth..makes it harder for me. Oh well its fun to learn and practice.

Other hard thing there is next to nill on the net to help model to 2.5D for cnc. I just went through the full 3d tutorial and started applying the basics I learned. Bottom line your time will best best spent on Moi, Silo and sculpting like sculptris/zbrush. Final thing that sold me was I started chatting with this guy a bit and he told me all I use is 3ds max and zbrush..some of thee nicest looking models for cnc I have seen. http://artline3d.ru

Good Luck