May07
2014

By: admin                Categories: 3D AnimationAnimation

One of the benefits of using ZBrush is how it speeds up the production process. For example, it is becoming common to skip creating concept art using pen and paper, or 2D software like Photoshop and jump right into sculpting a concept model directly in ZBrush. It is easy enough to try out several variations in ZBrush, and if the concept is approved you’ve already created the basic model! Using DynaMesh is one method for creating a fast sculpt; another is using ZSpheres.

To create a model using ZSpheres, start by selecting a ZSphere (the red twotoned ball) from the Tool menu and drawing it on your canvas. Now go into Edit mode (T key) and press the Q key to get into Draw mode.

Place your cursor over the existing ZSphere and draw out another ZSphere.

Press the W key to go into Move mode and move this new ZSphere around by clicking and dragging it. Notice how ZBrush adds more in-between ZSpheres to fi t the distance between the two? When you are working with ZSpheres, the normal draw, move, scale, and rotate transpose brushes take on different behaviors. You will no longer get the transpose action line when invoking these functions. Instead, simply clicking and dragging on any of the active ZSpheres will allow you to directly transform it. Try the different transform brushes out now. Press the E key to use Scale mode and click and drag on a ZSphere to scale it. Now try the Rotate mode by pressing the R key. Notice the difference between rotating a ZSphere and rotating one of the connecting triangular links between the ZSpheres.

Active ZSpheres show up as two-toned red spheres, while linking ZSpheres that create the ZSphere chain show up as a dull red color with a white triangle-shaped bone superimposed upon them. You can rotate the entire chain of ZSpheres without changing its shape by going into rotate or move mode and clicking and dragging on one of the white connecting triangles. If you move one of the active ZSpheres, the ZSphere chain will expand or collapse to adjust, adding or removing linking ZSpheres as needed. Using a very small brush size when moving, scaling and rotating ZSpheres will make it a lot easier to edit and allow you to be more accurate in your selections.

FIG 8.1 Draw a ZSphere on canvas

FIG 8.2 Draw another ZSphere on the first one

When you are in Draw mode ( Q ), the small circle that appears in the center of your brush when you have your cursor over an existing ZSphere shows you where a new ZSphere would start if you decided to draw it. The color of this small circle tells you whether or not you’re in a good spot. Green indicates a good spot, but when it is red you might end up with problems later on when you try to generate a skin from your ZSphere chain. If part of the ZSphere chain goes transparent or dark it is a warning that you need to rearrange your ZSphere positions to avoid future errors. Any of these mistakes could create geometry later on that is folded in upon itself, twisted polygons, or other problems.

You can refine your ZSphere chain by changing any of the linking ZSpheres to active ones just by clicking on them while in Draw mode. If you change your mind and want to get rid of any of your active ZSpheres, just hold down the ALT button while in Draw mode and click on the off ending active ZSphere to delete it.

FIG 8.3 Elements of a ZSphere chain

FIG 8.4 Good and not so good places to draw a new ZSphere

FIG 8.5 Click on a link ZSphere to turn it into an active ZSphere; ALT + Clicking a ZSphere deletes it

Go ahead and draw out a simple ZSphere chain to play with and get a feel for how they work. Start by drawing a new ZSphere tool on screen, going into Edit mode; then, making sure you are in Draw mode, simply draw another active ZSphere on the surface of the original sphere. Switch into Move mode using the W key and click and drag the newer ZSphere to where you want your chain of ZSpheres to end. Now you can switch back into Draw mode ( Q ) and add more active ZSpheres to your chain and move, rotate, and scale them into shape. If you need to draw additional ZSpheres coming off the chain, go right ahead. Be careful, though: once you start increasing the number of ZSphere branches coming off a particular parent ZSphere to more than a few you can start getting errors in your derived surface. If the ZSphere chain turns transparent, that is a sure sign that things aren’t going well and you should adjust those ZSpheres until they look normal again.

The white triangles between the ZSpheres, sometimes called links or bones, tell you how the diff erent ZSpheres infl uence each other. The ZSphere at the thick end of the triangle is the parent; the one at the pointy end is the child. Transformations – that is to say, movement, rotations, and scale – fl ow from the parent to the child, but not from the child to the parent. Basically, it is just a long-winded way of saying that if you rotate the arm the parent ZSphere is on, the child will rotate with it. The system is actually quite intuitive and it won’t take you much time of playing with it to make sense of how it works. Try drawing, deleting, and transforming ZSphere chains until you are quite comfortable with them. Nothing aids learning so much as doing.

FIG 8.6 Transparent ZSphere chains are a sign that something is wrong; adjust the placement of the active ZSpheres to fix the problem

There are two ways of converting your ZSpheres into sculptable objects. The first is called Adaptive Skin and usually yields good results. To see what your potential adaptive skin looks like for your ZSphere chain, simply press the A shortcut key or use the Tool.Adaptive Skin.Preview button. Press A or the button again to dismiss the preview. You can actually sculpt on the preview itself; but if you switch back into ZSphere mode and make any changes there, anything you have sculpted will vanish with the preview. To actually create a permanent version of the preview, click on Tool.Adaptive Skin.Make Adaptive Skin button. This will create a new tool in your Tool pop-up palette called Skin_ ZSphere , followed by a number in the name which will increment if you create additional skins. Now you can switch to your new tool and sculpt away. It’s a good idea to save your ZSpheres out, though; they can be useful for rigging any characters you’ve made with them later on. When creating or previewing your adaptive skin, you can use the Tool.AdaptiveSkin.Density slider to control the polygonal resolution of the resulting mesh. Higher numbers yield a denser and smoother result.

FIG 8.7 The ZSphere at the base of the link is the parent; the one at the point is the child

FIG 8.8 Adaptive Skin: Preview, Make Adaptive Skin, and the Density slider

The other option for generating a useful mesh from your ZSpheres is to use the Unified Skin palette found in the Tool menu. Unified skin isn’t as finicky as adaptive skin and you can just rough out a shape with your ZSpheres in practically any way you see fi t. When you’re finished with your ZSphere chain, simply press the Tool.Unifi edSkin.MakeUnifi edSkin button and observe the results. It is quite similar to using DynaMesh in that it just lays a polygonal grid over the ZSpheres to create the new skin. Adjust the various sliders in the Unified Skin menu to play with your results. Remember that ZBrush creates the new polygonal skins in the Tool menu icon list and you will have to switch your active model to one of the skins to see your results. It is all too easy to forget that ZBrush does this and create a dozen new models while looking for what’s on screen to change instead of looking in the Tool icon list.

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Excerpt from Getting Started in ZBrush by Greg Johnson © 2014 Taylor & Francis Group. All Rights Reserved.

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