Decimation & Remeshing for Beginners in ZBrush

Jul 22, 2021 at 07:00 am by Warlord720

Sooner or later, usually sooner, when you commit to 3D work you will run into a common problem. Trying to reduce the polycount of your beautiful and perhaps groundbreaking original model to an acceptable and usable polycount for use in a real-time engine like iClone and game engines.

This is a catch-22 of 3D modeling for those just starting out. You want detail but you need low poly. However, to get the detail you had to model in high poly. Usually, millions more than the engine will allow and that now needs to be a fraction of that polycount.

You jump right into whatever you can find… usually two tools come to mind at this stage and that is the ZRemesher and Decimation Master. The former will give you nicer quad topology but require more tweaking, creasing, protecting edges, and things of that nature or you will lose a lot of that precious detail you worked so hard to sculpt.

The latter will rough up your smooth mesh by using triangles as the final result but it can be overcome. Taken too far you might see the triangle-like facets in the face of the mesh… the lower the count the more prominent the triangular artifacts on the surface.

Poly Differences in Reduced Mesh
Left: Orignal Model 2,8 Million Faces, Middle: Remesh Model (Detect Edges) 130K, Right: Decimated Mesh (Freeze Borders): 33K

In fact, you may find yourself in a panic if you didn’t at least plan for low poly as the endgame. At this stage of the 3D learning curve, projection can be a wild concept that a lot of new users won’t grasp until they get more experience. The idea of projecting detail from a high poly model to a low poly model is usually not on the radar at this point. Unless you have a firm grasp of what needs to be done you can get into many “chase your tail” situations that end up being fruitless and frustrating leading to new users setting aside a powerful tool.

One thing to keep in mind is to not set an unrealistic goal for the reduction if the said reduction wasn’t on your mind at sculpting time. You may want or need a 35k prop, but you may have to settle for a 100K+ to keep detail until you learn more about how sculpting transfers to maps instead of mesh to bring out the detail of a high poly sculpt in a low poly environment.

There is nothing wrong with triangles unless you went too far in the decimation that the triangle won't bend where they need to… like say… the elbow or hand. In a prop… no big deal… as long as the prop looks good, and the textures are like you need it then all is well unless it’s animated then you might have to rethink it a bit and add more beef to the mesh as animation involves bending of some sort.

Reduction Results
Left: Orignal Model 2,8 Million Faces, Middle: Remesh Model (Detect Edges) 130K, Right: Decimated Mesh (Freeze Borders): 33K

At this stage... I would try to remesh one time at HALF or SAME just to see if I can maintain detail and get clean topology. However, there is nothing wrong with just relying on Decimation Master while keeping an eye on triangle size for animation and/or texture.

I decimate and remesh in stages. Sometimes I’ll go for the whole banana at once just to see what is possible but doing it a bit at a time like HALF instead of setting a target seems to work better for me. With Decimation Master… I usually work at the default 20 percent for the first few runs until I get to the point it’s no longer acceptable and then undo to get to a decimation point I do like.

M.D. McCallum, aka WarLord, is an international award-winning commercial graphics artist, 3D animator, published author, project director, and webmaster with a freelance career that spans over 20 years.  Now retired, M.D. is currently working part-time on writing and select character development projects. You can learn more about MD on his website


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