ZBrush Character Creation - Advanced Digital Sculpting 2nd Edition

■ Details and Layers 149

yield highest quality detail for high-resolution renders or when you need to create multiple
high-resolution color, normal, or displacement maps. This method is called high-density
(HD) geometry.
HD geometry is a method of dividing the mesh and sculpting in ZBrush that will sup-
port literally billions of polygons as opposed to the millions that standard subdivisions can
support. HD geometry works by allowing you to manipulate only a set number of polygons
at one time. The default is usually around 10 million. This means you can divide your mesh
into several billion polys but you will only be able to sculpt on 10 million at a time. Any
details sculpted or painted into HD geometry can be extracted into color normal or dis-
placement maps. HD can also be rendered inside of ZBrush by activating the HD Geometry
button under the Render menu. While HD geometry will render in ZBrush as well as export
into maps, there are two possible drawbacks: HD geometry will not work with layers and
you cannot export HD geometry as an OBJ file.
To use HD geometry, follow these steps:

1. Load the undetailed Stingerhead ZTool from the accompanying DVD into ZBrush.
   Draw it on the canvas and enter Edit mode.


2. Step up to the highest subdivision level. For HD geometry, I usually try and start add-
   ing HD levels at about SubD level 4 or 5. Since we are only going to add primary and
   secondary form to the standard subdivision levels, it is unnecessary to have a high poly
   count here. It also eats up memory from your performance in HD mode.


3. To add HD subdivisions, choose Tool → HD Geometry and click the Divide HD but-
   ton. At the top of the screen you will see a message telling you how many polygons are
   available. Figure 4.66 shows the result of four
   HD subdivision levels: 67.15 million polygons.
   While you can divide into the billions, keep
   in mind that the higher you divide here, the
   smaller your working area will be when you
   start to sculpt HD. I try to keep the number of
   polys in the high millions for most applications.
   To sculpt in HD, hold your mouse over the
   area you want to sculpt and press the A key. ZBrush
   will isolate a radial region consisting of the maximum
   number of HD polygons the system can display. This
   number is set by ZBrush during installation to an
   ideal value based on your system resources. You can
   change the value by selecting Preferences → Mem, but
   doing so is not recommended because it can cause sys-
   tem instability. Figure 4.67 shows a region of the char-
   acter ready for HD sculpting. The model will darken
   with a radial region of a lighter value—this is your
   active sculpting area.
   Select the standard brush and set your stroke
   to DragRect. From the Alpha menu, select the vein
   Alpha 22. Zoom into the active region as far as pos-
   sible and drag an instance of the alpha. You can see
   how finely detailed the surface can be. Create some
   texture on the active region (Figure 4.68).

Figure 4.66 ZBrush will report the total polygon count

of each HD level.

Figure 4.67 The active sculpting area in HD mode