If you've ever tried your hand at 3-D modeling, you know that it's a complex process involving weird tools and changing viewpoints. Pixologic's ZBrush 1.55b delivers sophisticated tools to would-be 3-D artists, but it provides them in a form most of us already understand: the paintbrush.

ZBrush's painting tools let you paint objects that have depth and dimension, but the program can't do all the things a true 3-D modeler can do (for example, lofting and extruding). It's really something of a 2-D-3-D hybrid, and its interface is a bit unusual. But once you figure it out, you can use it to create 3-D images fairly easily.

Z Painting

ZBrush is different from other painting programs in that it understands depth. While most 2-D programs concern themselves with a grid of pixels along the x and y axes, ZBrush adds a third axis, z, to create three-dimensional pixels called Pixols. When you paint with a ZBrush brush, the program understands where the resulting virtual paint sits in 3-D space. As you paint over earlier strokes, the paint builds up to create a 3-D "blob" that can be further sculpted and manipulated. By default, ZBrush images are rendered with lights and shading, so your 3-D objects have correct highlights and shadows.

Although ZBrush makes it easy to paint the layers of overlapping muscle in a sinewy forearm, for example, new paint sometimes inexplicably dives under preexisting paint, with unpredictable results. A paint blob may start out "deep," but painting across a "shallow" stroke can cause the brush to rise suddenly to the surface of the z-axis layers.

ZBrush's interface will also unsettle all but the most adaptable users. The unfamiliar placement of palettes, the unintuitive arrangement and naming of tools, and the often confusing icons (for example, spheres and circles are used liberally as icons for numerous unrelated tools) do little to help.

This program's 3-D facilities are innovative, but its basic 2-D-painting tools fall a little short. Expect to move your images into another painting or image-editing program for basic 2-D work. And although Pixologic's elaborate, scripted tutorials are an unusual and effective approach to teaching, the absence of straightforward documentation will frustrate newcomers who simply need to look up how to make something work as expected.

3-D Training Wheels

ZBrush's 3-D sculpting is great at helping you create elaborate organic forms, but it's a poor choice if you need to make accurate models of objects with more-exact measurements, such as a vehicle.

The Zspheres tool models an object by stringing together chains of spheres -- much as a traditional artist might block out the form of a human character by drawing circles. You can then stretch a smooth polygonal skin over this form to create a single continuous shape. But while Zspheres are impressive, they don't let you build circular overlapping chains, so you can't really use them to model a body, for example, where bunched and connected muscles are covered by a single layer of skin.

Macworld's Buying Advice

We like ZBrush's innovative support for painting with depth, but the interface leaves lots of room for improvement -- and the program can't replace Adobe Photoshop or a full-featured 3-D application. If you need an easy-to-use 3-D-modeling facility, it's a great tool to have, as long as it isn't the only 3-D brush in your tool kit.