ZBrush Character Creation - Advanced Digital Sculpting 2nd Edition

■ Alphas 135

Your Alpha Library

To have ZBrush load your favorite alphas by default into the Alpha menu directly, simply copy

them into the Pixologic/ZBrush4/ZStartup/Alphas folder. The alphas cannot be in a sub-

folder; they must be in the root Alphas folder. Any images in this location that are readable

in ZBrush will be loaded at startup into the User Alphas section of the Alpha palette. Keep in

mind that they will always load into memory, so you will want to keep only your most often used

alphas here. Any other alphas are best stored in the Lightbox.

Sculpting Alphas in ZBrush

There may be occasions when you need a specifi c kind of surface texture that you cannot
fi nd in photo reference. Or perhaps you have two alphas you want to combine into a single
alpha. In these cases, you can use ZBrush’s 2.5D canvas to sculpt the texture you want by
hand and then capture the sculpted detail to a grayscale alpha.
To use the brush document window to sculpt your own alpha, follow these steps:

1. First resize your document to 300×300 pixels. From the Document menu, click the
   Pro button to disable Constrain Proportions. Click in the Length slider to activate it,
   and enter 300. Repeat the same process for the Width slider. Now click the Resize
   button to create a new canvas that is 300 pixels square. Alphas need to be square so as
   not to distort when redrawn with the sculpting brushes. If you intend the alpha to be
   used only as a stencil, it can be any proportion.


2. You now need a surface on which to sculpt the alpha. Since the alpha is derived from
   depth information, you want to select a fl at surface on which to sculpt. From the Tool
   menu, select the Plane3D icon. Click MakePolymesh3D and draw the plane on the
   canvas. Enter Edit mode and divide the plane as high as possible by pressing Ctrl+D
   with SMT turned off. With SMT off, the plane will remain square while it is divided.
   Or you can choose Tool → Geometry and click the Divide button. You want as many
   subdivisions as possible to support the fi ne details we’ll sculpt in the next step. Note
   that the material selection will have no effect on the alpha created in this step—your
   surface material can be anything you prefer. In this case, I used White Cavity.


3. Scale the 3D plane up to fi ll the canvas window.
   Now select the Standard brush and Alpha 01.
   From the Stroke menu, select Freehand. Begin
   to sketch in a wrinkle pattern on the 3D plane.
   In Figure 4.33 I have sculpted a crosshatched
   wrinkle pattern suitable for high-frequency skin
   texturing.


4. When you have completed the sculpt, select the
   Alpha menu at the top of the screen. Scroll to the
   bottom of the menu and click the GrabDoc button.
   This button grabs a snapshot of the ZBrush canvas
   depth information. Remember that ZBrush’s can-
   vas is depth enabled, so the 3D plane will be read
   as white (no displacement) whereas your strokes
   will be captured as shades of gray.

Figure 4.33 Sculpting a wrinkle

pattern