Daniel Newman's Thesis Development Blog: DIGM 620

I have (more or less) figured out the final part of my photogrammetry workflow. Previously, I was generating a model that was an incredibly dense topology and an ugly UV Map. Large models take up a lot of memory and made online sharing and management an issue. For this reason I have been seeking a way to create a low polygon model that maintains most of its texture details. I have heard about ways of doing it, but finding the exact combination of tools has proven allusive. I had experimented with Mudbox, but I ended up hitting a way. Finally with ZBrush I took my high-poly model through towards completion. Let me show you my procedure.

First bring your obj (exported from Meshlab) into Zbrush.

Go into the Texture Map menu and upload the texture map (also from Meshlab)

You might want to switch your material to a flatshader so that you can see your material

To make the texture information transferable, we need turn that Texture Map information into intermediary Polypaint information. First add a few subdivisions to your model (keep it around 1 million polygons), then hit the "Polypaint From Texture" button. The roundabout pathway is this: Begin with aTexture Map > Turn it into Polypaint > Turn it back into a new Texture Map.

Next duplicate your object so that you have a second subtool. This will be the low-poly mesh that will receive all texture information. To make a quick low-poly mesh, use something like ZRemesher.

Here is my reduced mesh.

At this point you should have two subtools: your original high-poly mesh and one reduced copy.

This new mesh doesn't have a defined UV Map, so let's go to the UV Master Zbrush plugin menu. It will ask you to work on a clone (a third-mesh). There are a diversity things you can tweak in this menu, but for simplicity just hit Unwrap and see what happens.

Here is cloned mesh. The orange lines show seambreaks.

When satisfied, copy your UV maps (there is a button) and then past them onto your low-poly model. Your low-poly mesh now has a UV map and so can hold a texture map of its own. The UV map is also much clearer and neater then the source model's map.

With your original mesh as the top subtool and your low-poly mesh below it and selected, hit the ProjectAll button. This will project details and texture information from the top model to the bottom. I only tweeked the Dist slider (from default of 0.02 to .2)

If this menu pops up, then it probably worked. Hit Yes.

After projection, here are the two models. On the left is the original mesh (299,190 faces, 64.3 MB) and the reduced mesh (10,968 faces, 1.6 MB). It's a quite large reduction in size but at a minimal loss in detail.