model scaling and displacement problems

[system]

Hey there, first post. I’ve only just started using zbrush so hopefully this is a noob question which can be easily solved I looked through the faq and didn’t find anything which seemed to answer my question so here goes.

I’m trying to sculpt some creases for a leather jacket for a character i’m making in Maya. To start with i’d scaled my character in Maya to match a real world height (ie, about 6 ft) because i’ll be using GI in my renders and i’ve heard scaling models of chars/envs to real world proportions gives better results.

After UV’ing the jacket i imported it into zbrush as an obj, but when i tried to subdivide it the model flipped out and was a mess. I found i could solve this by scaling the model down in maya significantly, to about 0.01 of its previous size. Once this new smaller model was imported into zbrush it subdivided fine.

Firstly any explanation of why this happens would be useful

So i did some random test sculpting and created the disp map using the tut here:
http://www.zbrush.info/docs/index.php/Creating_Displacement_Maps

The tiff file generated by the disp was almost completely mid grey with little or no indication of the actual map, this would happen whether i set my intensity to 0.1 or 512…any explanation of this would also be handy!

so i applied the image as a displacement to my (scaled down) model in maya and it comes out as a big blob with the disp obviously overpowering the original model. When i tried scaling my model back up to 1 again the displacement no longer blew out the model. You could now almost see the sculpting but it is now far too weak and low resolution ( see image ). The disp map resolution was 2056 sq

I’m basically just trying to get a handle on the displacement workflow and solve these problems before i start seriously sculpting otherwise i could waste a lot of time making something which won’t work. Any pointers on getting this right would be very helpful…thanks in advance!

Attachments

[aurick]

The model getting freaky when you divide it is probably due to a scale issue. In ZBrush, look at the Tool>Preview window. How big is the model relative to the window? Probably really large.

Maya may have an export setting that can scale the model down by a certain factor when you export it. That’s the best way to go. Alternately, in ZBrush you can use the Tool>Deformation>Size slider to scale the model after you’ve imported it. By using that slider, you can decrement the model by a specific amount, which lets you scale it back to what you started with if you’re going to need to export the model again. (For example -75 would leave it at 1/4 size. Size 100 twice would then return that to original size.) Of course, if you’re only going to need to export the maps and won’t need to export the model again you can simply use Tool>Deformation>Unify instead of messing with Size.

Regardless, be sure to store a morph target after rescaling and before subdividing. When you return to level 1 to create your displacement map, switch to the stored morph target. This restores the original base mesh without any influence from multi-resolution division smoothing. It’ll give you the most accurate displacement map and avoid bloat in your render.