A common problem that new users encounter (which is the first hurdle that any new ZBrush user has to overcome) is when a 3D object is finally "snapshot" to the canvas. Below is a description of why you can't pick up an object once it is snapshop.

It was written by Mathew Yetter in answer to a member of the ZBCentral forum and I think it explains it very well.

It's these additional tools that give ZBrush scenes such amazing quality compared to other 3D programs. The rest relies on textures and lighting. What ZBrush does is to allow you to take the scene even further, painting additional detail into the scene like a 2D program but doing so with the depth of a 3D program.

All of which brings us back to the fundamental hurdle; the fact that once snapshot it is very awkward to try and pick an object up again. Imagine this: you snapshot a sphere to the canvas and then use the Cone3D to add spikes to it. Next, you use other 2D and 2.5D tools to add additional details to this spiked ball. Now what would happen if you were to pick the initial sphere back up again? What's the program supposed to do with all of that other stuff that you just painted on? It's not a part of the geometry. It's not a texture, either, since it has depth of its own. The processing power to move all of that other stuff in 3D while you work on the sphere some more would be horrendous -- if your computer could even handle it, real time rendering would go right out the window.

So in the end, while it is inconvenient in some ways to try and get used to ZBrush's unique way of doing things, those wacky methods are all there for a reason. They let ZBrush do what no other program can do. Along the way, they also happen to really benefit other programs (such as by making it easy to create morph targets, textures, or original 3D models). They also allow ZBrush to be a mighty fine rendering engine all by itself. And, of course, everything works together beautifully to allow artists to create amazingly detailed and realistic scenes from start to finish in ZBrush in far less time that it would require in another app.

It's just a matter of "unlearning" a few techniques and thinking in a new way...

above text © Mattew yetter used with permission
Visit Mattews site 'The Aurickle' to see some of his work

In these tutorials you will beging to construct an entire head, the 'Purple Nasty'. To combine the head, eyes and teeth I needed to use multiple layers to separate the objects with differing materials. Unlike other programs with layers in ZBrush it does not matter which layer is in-front of which, because each layer has its own depth.

A ZBrush image is built up as shown on the left. All objects start out on the clipping plane and can be moved in and out of the image. Once in (snapshot) they are there for good, remember!.

With layers it is possible to put a head into the image on one layer and the eyes in on another. Even thought form your perspective thet overlap, one cannot effect the other. THis allows you to paint on an object in one layer and leave the other layers untouched.