It used to be true that if a modeler was familiar with a sculpting application and could incorporate very high-resolution details into a model, it was considered a bonus. Those days are long gone. Having a sculpting application in your modeling toolbox is a must at this point, so it's just a question of which one to use. Let's look at two of the big players, ZBrush and Mudbox to see how they stack up.
In order to sculpt a model, you first need to have some base geometry to work with. This geometry can be imported from other applications or created in the sculpting app itself.
ZBrush has a ton of mesh creation options available. You can use ZSpheres to build up character bodies or complex creature shapes by creating virtual armatures. ShadowBox will allow you to use masking to quickly create complex hard-surface pieces that are formed from intersections between those masks. DynaMesh will give you the ability to cut apart and reassemble your meshes very easily. In addition, you can import any base geometry you create in other applications.
Mudbox is more limited in the mesh creation realm. When working with Mudbox, you'll likely bring in base meshes from another program like Maya or 3ds Max. To make this easier, there is a very close integration between Mudbox and other Autodesk applications. In addition, you can use Retopologize to create base shapes from sculpted forms. In the end though, for sheer number of options and flexibility, the mesh creation edge goes to ZBrush.
ZBrush provides a huge number of custom brushes, with many more available through the LightBox browser. There are brushes meant to pull out overall shapes (Move) and to build up material on the surface (ClayBuildup) You'll aslo have the ability to create sharp creases or edges using brushes like DamStandard. There are also a wide range of options for modifying brush parameters and stroke types as well as the capability to modify strokes using curves. Although the 2.5D canvas is a little different than working in a traditional 3D viewport, the sculpting process is smooth and reactive.
Mudbox offers the same basic brushes as ZBrush. You can move geometry using the Grab brush or build up material using the wax brush. The brush parameters are more limited but very focused on the things you'll often need.
One aspect of sculpting where Mudbox really shines is in the use of vector displacement maps as stamps. With the included maps you can quickly create detailed creases with undercuts/overlaps and you can also easily create your own. The VDM stamps are absolutely amazing in Mudbox, but due to the amount of brushes and parameters available, ZBrush gets a slight edge over Mudbox here.
So far, it looks like ZBrush is running away with it. Not so fast! Texture painting may or may not be part of your workflow but it's an important aspect of what these applications do.
ZBrush uses polypainting to create textures, basically coloring the model based on its resolution. So a highly detailed texture requires an equally high-resolution sculpt. In addition, the painted detail doesn't exist as a texture map until you export it. On the positive side, you don't have to worry about UVs until later and you can sculpt and paint at the same time.
Mudbox offers a full-featured, layer-based texture painting workflow. Each map is assigned to a material channel and each channel can have multiple layers blended together. This is a more traditional workflow and is really easy to comprehend. It's also not tied to the resolution of the model.
Another positive is that Mudbox allows you to see the effect of your maps on the model immediately, even if you're painting other channels like Specularity or Incandescence. As a bonus, you can also forget about UVs all together and paint textures using Ptex. Because of this, Mudbox has a clear edge here.
A vital part of any sculpting pipeline is the act of creating new, optimized topology. This new topology will be the actual mesh used in production with the sculpted detail and painted textures applied as maps. ZBrush and Mudbox both have methods for creating this new topology over the top of your sculpts.
There are automated methods that will quickly create a new mesh based on guides and polygon count parameters. ZBrush uses ZRemesher while Mudbox calls its function Retopologize. There are also ways of drawing out the new polygons yourself. ZBrush's retopology tools have been around a little longer, so it has a slight advantage here.
The calculation of normal or displacement maps from your high-resolution sculpt is one of the final steps in the sculpting process. These maps are created by comparing the high-resolution sculpts and the lower-resolution, retopologized production geometry.
ZBrush goes about this in an unusual way. You need to subdivide the new mesh and project the detail into the subdivided geometry. You can then calculate your normal or displacement maps from there. The workflow is a bit different from Mudbox and from other 3D applications that offer map baking functionality.
Mudbox, on the other hand, allows a lot of flexibility in baking maps. You can use different levels of the same mesh or completely different geometry. There are a variety of bake settings and these are automatically saved for reuse. Mudbox gets the nod here.
The Winner Is...
You! (I know, what a cop out!) As modelers and artists you all win when you have great tools to work with. Whether you work in ZBrush or Mudbox, either (or both) of these applications would make a valuable addition to your modeling arsenal. Depending on what kinds of projects you work on, or how you prefer to work, you'll likely be drawn to one or the other.
Which program do you prefer? What parts of your projects are easier to do in Mudbox or in ZBrush? Which workflow quirks drive you crazy? Let us know in the comments below and let the battle rage on!
Note: ZBrush and Mudbox aren't the only options you have for sculpting geometry. All-around 3D programs like MODO, CINEMA 4D, and Blender all have integrated multi-resolution sculpting solutions. You can also pick up 3D Coat, Sculptris or smaller apps like 123D Sculpt. In fact, you can even sculpt right on the web using SculptGL.