Meshlab polygon reduction by Xuan Prada

Meshlab is probably the only available solution (proprietary Lidar software doesn't count) when you have to deal with very heavy poly count. I'm working with some complex terrains, some of them up to 50 million polys and Maya or Zbrush just can't handle that. I'm reducing the poly count considerably fast in Meshlab with its polygon reduction tools.

  • This terrain has more than 16 million polys. Maya can't handle this very well, and Zbrush can't manage memory to even open it. Just import it in Meshlab.
  • You will be using the Quadric Edge Collopse Decimation tool a lot.
  • There are different strategies available, I like to use the percentage one. In this case by 0.5
  • I'll be getting an 8 million poly terrain.
  • I just run the tool one more time to get a 4 million terrain. I can work in Maya with this :)

Dealing with Ptex displacement by Xuan Prada

Render using Ptex displacement.

What if you are working with Ptex but need to do some kind of Zbrush displacement work?
How can you render that?

As you probably now, Zbrush doesn't support Ptex. I'm not a super fan of Ptex (but I will be soon) but sometimes I do not have time or simply I don't want to make proper UV mapping. Then, if Zbrush doesn't export Ptex and my assets don't have any sort of UV coordinates, can't I use Ptex at all for my displacement information?

Yes, you can use Ptex.

Base geometry render. No displacement.

  • In this image below, I have a detailed 3D scan which has been processed in Meshlab to reduce the crazy amount of polygons.
  • Now I have imported the model via obj in Zbrush. Only 500.000 polys but it looks great though.
  • We are going to be using Zbrush to create a very quick retopology for this demo. We could use Maya or Modo to create a production ready model.
  • Using the Zremesher tool which is great for some type of retopology tasks, we get this low res model. Good enough for our purpose here.
  • Next step would be exporting both model, high and low resolution as .obj
  • We are going to use these models in Mudbox to create our Ptex based displacement. Yes, Mudbox does support Ptex.
  • Once imported keep both of them visible.
  • Export displacement maps. Have a look in the image below at the options you need to tweak.
  • Basically you need to activate Ptex displacement, 32bits, the texel resolution, etc)
  • And that's it. You should be able to render your Zbrush details using Ptex now.

Clarisse UV interpolation by Xuan Prada

When subdividing models in Clarisse for rendering displacement maps, the software subdivides both geometry and UVs. Sometimes we might need to subdivide only the mesh but keeping the UVs as they are originally.

This depends on production requirements and obviously on how the displacement maps were extracted from Zbrush or any other sculpting package.

If you don't need to subdivide the UVs first of all you should extract the displacement map with the option SmoothUV turned off.
Then in Clarisse, select the option UV Interpolation Linear.

By default Clarisse sets the UVs to Smooth.

You can easily change it to Linear.

Render with smooth UVs.

Render with linear UVs.

Mudbox and UDIMs by Xuan Prada

When you’re going to texture an asset which already have a displacement map, probably you’ll want to apply that displacement to your mesh before start the painting process.

In my pipeline, I usually apply the displacement map in Mudbox and then I export the high resolution mesh to Mari.

The problem here is that Mudbox doesn’t allow you to work with displacement maps and multiple UV shells.

I tried below to find a solution for this problem.

  • Check your UV mapping in Maya.
  • I’m using these simple displacement maps here.
  • One map for each UV shell.
  • Export as .Obj
  • Open in Mudbox and subdivide.
  • Go to maps -> sculpt model using displacement map.
  • Select your mesh and your displacement map.

As you’ll realize, Mudbox doesn’t allow you to choose different maps for each UV shell which means that Mudbox will be able only to sculpt using the displacement map for U0-1 V1-0 coordinates. Big problem.

The way which I’ve found to solve this problem is:

  • Go back to Maya.
  • Select your mesh and open de UV Texture Editor.
  • Select one of the UV shells which is outside of the default U0-1 V1-0 range.
  • Open the script editor and type -> polyEditUV -u -1 -v 0 ;
  • You’ll notice that the second UV shell is placed in the default UV shell but was moved 1 exact position. Then your displacement texture  will match perfectly.
  • Export again as .obj
  • Now you’ll can use your displacement map in Mudbox without problem.
  • Repeat the process for each UV shell.
  • Commands to move UV shells 1 exact position.

Move left -> polyEditUV -u -1 -v 0 ;

Move right -> polyEditUV -u 1 -v 0 ;

Move up -> polyEditUV -u 0 -v 1 ;

Move down -> polyEditUV -u 0 -v -1 ;