ZBrushCentral

Displacement Map Inconsistency

ZBrush Usage Questions
#1

Hi,

I have a displacement map problem that I can’t get to the bottom of.

Here are two displacement maps for a female torso:

I detailed the abdomen and exported the displacement map to Max, eveything was as expected (first image on left). I went back added a few minor details and re-exported. I ended up with the second map (to the right).

The left map is what I want - it just contains the data for the extra detail added in ZBrush. The second map contains displacement data as some sort of mean of the whole model - for example, I have not detailed the back in ZBrush, that detail is from the reilef of the base mesh.

As far as I am aware I changed nothing, although I have since tried changing settings to no avail. Why would I get two such different results with seemingly the same technique?

How can I make ZBrush ignore the base mesh and simply render the added relief to the displacement map, as in export 1.

I’d massively appreciate a heads up on this.

Cheers,
Dave

#2

I suspect that your issue is due to what happens with multi-resolution mesh editing.

When you divide your mesh, catmull-clark rules cause it to contract a little. When you return to level 1, that contraction is translated down to level 1 as well. Your model will now be slightly smaller than what you started wtih.

To counteract this, you should store a morph target before you divide the model. When you return to level 1 you can switch to the stored morph target to get your original cage mesh back again. Now create your displacement map.

If you need to return to higher levels, switch morph targets again. Otherwise, the larger level 1 will translate back up the mesh and inflate the higher levels. When you later return to level 1, switch back to the stored morph target.

By using this workflow you will be able to maintain consistency in your maps.

#3

This same thing has been happening and causing me hours of debugging time. Seems like at complete random - maybe one in 40-50 times - ZB will export the map correctly. (only concerned with displacement maps)

I’ve tried every variation of exporting maps, storing morph targets, importing/exporting models, etc.

Thought that perhaps it had to do with storing morph targets on layers throughout my sculpting process. Do layers even record MT’s?

Using ZBrush4. My mesh has tiled uv’s so i have to use MME. Although, like I said, for testing purposes, I tried the Displacement Map menu under Tool Palette - same thing happens.

Trying MME and also the 16bit Disp exporter w/in the Tool Palette’s ‘Displacement Map’ menu. Same results…which leads me to think there’s a problem with whatever ZB is doing when it subdivides the mesh as it generates a displacement map.

Is there a known inconsistency to the fine folks of Pixologic in the way ZBrush 4 is generating displacement maps??

This has happened to me several times in the past - fortunately, for those times I’ve been able to paint out the unwarranted displacement generation. This time, I cannot. I’m working on a large feature production and need to get this resolved. Unfortunately I cannot send a file for testing. Please, help you can offer would be great. Thanks!

r

#4

After further testing, it seems like the maps are representing the difference b/w original base mesh (which I’m importing at level1) and subdivided mesh. It’s doing this regardless of whether I import the base mesh, store a morph target, whatever…

I even turned off ALL sculpted details and the differences in topography were STILL recorded in the displacement map.

Tried:

  1. Dropping to level 1 on sculpted ZTool
  2. Storing a MT
  3. Importing original base mesh (did NOT step back up in subdivisions before generating map)
  4. Generating 16bit disp with SwitchMT on AND off.

…and many, many other variations