ZBrush and Working with Imported Meshes (Designing a Character Bust) (ZBrush Character Creation) Part 1

While sculptures started from ZBrush primitives can be rebuilt into animation-ready meshes using the ZBrush Topology tools, in some cases you will want to start from an imported mesh instead. You may have a generic head or body model, or perhaps a generic animation-ready base mesh is used for all the characters in your pipeline.


In this topic, we will import a polygon mesh from a third-party modeling package. It will be a relatively simple humanoid head mesh from the Pixologic website. The mesh is from a selection of meshes modeled by Ang Nguyen and made available for free. Please check the accompanying DVD for these models. In this topic we’ll create two character busts.

I’ll walk you through the steps involved in designing and sculpting the primary and secondary forms; we’ll talk detailing in the next topic when we cover alphas and texture stamps.


In ZBrush, models are 3D meshes that are imported into ZBrush to become ZTools. The difference between ZTools and models is that a model is just a 3D mesh file that contains polygons and UV information. A ZTool is ZBrush’s native file format for sculpted objects. A ZTool can contain multiple levels of subdivision, high-resolution sculpting details, texture, and polypaint information, as well as alpha maps and layer data. The ZTool format allows you to store far more than just an OBJ file.

Models are imported into the Tool palette where they become available with the other ZTools listed there. When importing models into the Tool palette, it is important to be sure your mesh is optimized for detailing in ZBrush. If your mesh is ordered and animation ready, or is part of an existing production pipeline, you may not have the freedom to lower the initial polygon count. The edge flows and topology have already been approved for rigging and animation. When loading a model into ZBrush, you must understand how ZBrush determines subdivisions levels and where the system limits are.

Physical memory is the most important deciding factor in determining your highest subdivision level, followed closely by processor speed. ZBrush is not concerned with graphics cards, and multiple processors are only useful when moving the model around the screen and sculpting. ZBrush uses the amount of physical RAM installed on the system to determine the highest possible subdivision level attainable. The processor comes into play when you start to rotate and manipulate the sculpture onscreen. A faster processor will allow you to move more polygons with less lag.

You can find the maximum subdivision level that ZBrush has set for the machine by choosing Preferences + Mem. The MaxPolyPerMesh slider will show the value in terms of millions.If you raise the MaxPolyPerMesh value slider, be sure to raise the CompactMem slider to 256, 2048, or 4096. Doing so increases the amount of memory ZBrush will use before starting to write temp files to the hard drive, which slows down performance.

The question arises of how to ensure you get the maximum subdivision levels from ZBrush. Often an artist will load a mesh for sculpting only to find that it subdivides to a level that is unsatisfactory to get the level of detail desired. Starting with a lower polygon count can help ensure you reach the highest possible subdivision level. This approach works because of the algorithm ZBrush uses to subdivide.

ZBrush uses Catmull-Clark subdivision each time you click the Divide button. This means that for each subdivision level, ZBrush multiplies the total polygon count by 4. So if level 1 is 4,000 faces, level 2 will be 4,000 x 4. That gives you a level 2 poly count of 16,000. If this mesh were divided again, ZBrush would multiply 16,000 by 4, giving you a level 3 polygon count of 64,000. If your initial poly count at level 1 were 17,000, you would reach 1 million faces by three subdivisions. Unless you set your MaxPolyPerMesh slider to something above 4, you would not subdivide again as the fourth subdivision level would be over 4 million.

Underlying topology can become a concern in ZBrush if your edge loops define forms that you choose to change later. There are times where your topology may fight the forms you are trying to make. Because of this, simple block models can be beneficial when working in ZBrush. They offer extremely simple bases that can be moved at the lower subdivision levels easily as well as subdivided up to millions of polygons for fine detailing.

The Mem preferences

Figure 3.1 The Mem preferences

Once the sculpture is completed, these meshes can easily be retopologized to any mesh resolution you desire. This helps keep the sculpting process separate from polygon modeling and allows you to focus on topology and technical concerns after the design phase is completed. The leg in Figure 3.2 illustrates how much form can be pulled from a simple block model. Figure 3.3 illustrates just how little underlying topology is required to create a detailed character sculpt. This demon head was sculpted entirely from a polysphere in ZBrush. The benefit of this technique is that you have total freedom to move shapes around, but the possible drawback is that it can be harder to detail areas like ears, horns, and noses—any part that is stretched too far from the original sphere shape.

A leg sculpted from a box model

Figure 3.2 A leg sculpted from a box model

This demon is sculpted entirely from a single polysphere.

Figure 3.3 This demon is sculpted entirely from a single polysphere.

Organized meshes are models that have been specially built for animation. They have edge loops containing major muscle forms and areas of deformation (Figure 3.4). When reto-pologizing a design sculpt, you will strive to create an organized mesh. It is often the case that organized meshes are built before the sculpting phase. This is a valid approach, but I find that it limits the sculpture and can limit the subdivision levels in some cases. Organized meshes work best for animation, whereas sculpting can benefit from a much simpler mesh.

A mesh organized for animation

Figure 3.4 A mesh organized for animation

If you have holes in your base mesh that you want to maintain—for instance, a head that is separated from a shirt—you will find smoothing in ZBrush will cause the border edges to shrink. To correct this when you import your base mesh, click the Geometry Crease button under the Tool menu. This will tag the border edge of the geometry and keep it in place while smoothing the rest of the model.

Other options for generating meshes directly inside ZBrush include the tools ZSpheres and ZSketch. ZSpheres allow you to create organized polygon meshes quickly by drawing interconnected chains that are converted to polygon meshes. Although ZSpheres do not offer the same control of edge placement that direct polygon modeling does, ZSpheres use certain controls to create form and edge loops. The resulting models are light, organized, and ready for subdividing and sculpting.

ZSketch, on the other hand, allows you to create models by building up volumes with successive brush strokes. The meshes generated from ZSketch are denser than ZSphere meshes and usually require different working methods. Figure 3.5 shows examples of both ZSphere and ZSketch meshes.

 A ZSphere model on the left and a ZSketch model on the right

Figure 3.5 A ZSphere model on the left and a ZSketch model on the right

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