View Full Version : ZBrush to LW displacement artifact

09-03-2007, 10:33 AM
Hi, I've been experimenting this week trying to build the pipeline between ZBrush and LW (9.3). I started with a blocky dinosaur model I built in LW, imported it into Zbrush and did some work on the head and neck.

After a lot of trial and error with the 16 bit tif displacement map I finally managed to get the model in Layout to have some resemblance to the zbrush version:

Here's the problem, in ZBrush, I only sculpted the head and about halfway down the neck, so where's the woodgrain pattern on the arms and body coming from? The woodgrain is actually on the entire model, including the head, it's just harder to see because of the sculpted displacement.

If I lower the intensity of the displacement, the grain is less visible, though still noticable, but unfortunately my dino doesn't look much like he did in ZBrush anymore:

Maybe there's something about the displacement map that I don't understand, in theory, in areas where I haven't done any sculpting in zbrush, it shouldn't have any displacement info should it? It should have no effect on areas of my model that I haven't sculpted.

Any suggestions welcome,

David R

09-03-2007, 11:40 AM
What type of subaptches are you using and what is your subdivision order set to?

09-03-2007, 01:27 PM
Are you using GUV or AUV tiles for your UV cords? You could try a 8000x8000 displacement too but that may be unnecessary for a medium shot, but for close ups you may need larger than 4096 or multiple disp maps, though that complicates seam issues. On the other hand you could have missed a step in your process. As for that seam, yeah that's what happens when you use discontinuous polygons/ edges in your topology when using Subpatches.

09-03-2007, 01:30 PM
Another tips is that if you can avoid using triangles with displacements, do it. I especially have gotten nasty displacement errors where there are triangles when using Catmull Clark. Aside from the seams with Subpatches they tend to work better with Displacement Maps.

09-03-2007, 03:38 PM
What type of subaptches are you using and what is your subdivision order set to?
The images were rendered with the normal sub-d type. I've also tried Catmull-Clark, which looked the same, still woodgrained.
Subdivision order set to First. After Morphing and After Bones look exactly the same as First. After Displacement, After Motion, and Last, not surprisingly just show up as the base mesh with no displacement at all.

switch the base mesh to Catmull-Clark mode before displacement mapping.
Tried this, no effect on either woodgrain or seams. I was aware of the seam issue, I've seen posts about it, so I wasn't concerned with those yet.

What resolution is your displacement map?

Are you using GUV or AUV tiles for your UV cords?

Use a higher detail mesh from your ZBrush tool, something like level 2 or 3
I've had that same thought, but haven't been able to try it yet.

Though I still don't understand why ZBrush is generating a displacement map that has some sort of displacement info (woodgrain) in areas of the model where I've done no sculpting at all. I can see on the displacement map that areas that I would have assumed would have just remained gray, have lighter areas on them. Which makes no sense to me considering I haven't done anything to the model in those areas.

Which makes me think the woodgrain problem is connected to ZBrush, not LW, since it's coming from the ZBrush generated displacement map.

David R

09-03-2007, 06:08 PM
okay, a 4096+ disp map would definately help

My guess is that you don't have enough polygons in your Zbrush Mesh. I usually work with 6 to 14 million polygons with a charcter that needs quite a bit of detail. Wrinkly things like a Dino would definately benifite from this. You really shouldn't go bellow 4 million polygons for a single displacement for an entire Dinosaur, even for a farther shot.

09-03-2007, 06:10 PM
btw, the AUG or GUV Tiles will give you a lesser quality UV map in my opinion. I get artifacts all the time using that stuff. Best to unwrap with the UV PLG tools,