Alphas (ZBrush for Detailing) (ZBrush Character Creation) Part 4

ZAppLink Stencils

Stencils for complex mechanical shapes are easy with ZMapper. By defining a custom selection in Photoshop, you can generate a stencil back in ZBrush. Use the following steps for this process:

1.    Create a Cube 3D primitive from the Tool menu. Click Make Polymesh 3D and draw the tool on the canvas. Enter Edit mode and subdivide as high as possible.

2.    Center the cube in the document window and press Ctrl+Shift+S to call ZAppLink. Deselect all the check boxes in the ZAppLink window that appears and click Drop Now. ZAppLink will open Photoshop and load a copy of your ZBrush document (Figure 4.28).

Figure 4.28 The ZBrush document transferred to Photoshop with ZAppLink

3.    Create a selection in Photoshop, and save it by choosing Selection ^ Save Selection. Name the selection stencil (Figure 4.29).

4.    Save the Photoshop document and return to ZBrush. When you return to ZBrush, click the OK (Unchanged) button, and your stencil will automatically load and apply to the model.

You may now sculpt through the stencil to create hard-edged details. By repeating this process with multiple selections, you can build complex shapes quickly and easily (Figure 4.30).

Figure 4.29 Create a selection in Photoshop and save it as stencil.

Figure 4.30 Mechanical details built from ZAppLink stencils

Importing Images to Use as Alphas

Any image may be loaded into ZBrush and used as an alpha. The file formats ZBrush supports for import are PSD, BMP, and 16-bit TIFF (single-channel grayscale). To import an alpha, open the main Alpha menu at the top of the screen and click the Import button. Browse to the file you want to load.

There is no shortage of great texture references that can be used as alphas: on the Internet, in topics, even around you. Try taking photographs of plants and fruits for use as texture stamps. For the best all-around skin alpha set, I recommend checking ZBrushCentral. Rick “Monstermaker” Baker made some of his skin alphas available in his Old Man thread. This is a fantastic selection of pore, wrinkle, and bump alphas.

When a photograph is loaded into the Alpha menu, it is automatically converted to 16-bit grayscale. In the Alpha menu beneath the active Alpha boxes are several sliders that allow you to postprocess the alpha and make various alterations to the image. With these modifiers, you can maximize the range (similar to autoleveling in Photoshop) by crunching the levels, thus giving you the maximum displacement between black and white. You can also use the Blur slider to slightly blur your image, removing artifacts from JPEG compression or other noise. See Table 4.1 and Table 4.2 earlier in this topic for a description of what each of these menu options does.

Figure 4.31 This image of skin texture can be applied directly to your model as an alpha texture stamp.

In this section we’ll import an image of skin detail and use it as an alpha (Figure 4.31).

1.    From the accompanying DVD, load skinswatch.psd into the Alpha menu by clicking Import.

2.    This is a skin detail from a photograph. To optimize it for use in ZBrush, click the Max button in the Alpha menu. This will maximize the value range to help you get better details. You will also want to raise the Rf slider to 10 to add a faded border. This prevents the alpha from leaving a square artifact when used.

3.    From the Lightbox ZTools menu, select the Polysphere tool and draw the sphere on the canvas. Enter Edit mode and divide the sphere as high as possible on your system.

4.    Select the Standard brush, set ZIntensity to 12, and select the DragRect stroke and the SkinSwatch alpha. Drag the alpha on the surface. Figure 4.32 shows the sphere with the custom pore alpha applied.

Figure 4.32 The custom SkinSwatch alpha applied to a sphere with a DragRect stroke

5. The image file has a bit of noise from both JPEG compression as well as high-contrast lighting. You can reduce this noise with the Blur slider. Raise Blur to a value of 2 and redraw the stroke. Try adjusting the other sliders such as Contrast and Noise.

Baking Changes to the New Alpha

It is important to understand that changes made with these sliders are applied as a process to the imported alpha. If you want to save the alpha with these changes applied, you must “bake” them into a new instance of the alpha. To save a modified version of the alpha, follow these steps:

1.    With your alpha active in the Alpha palette, set the modifiers you want to adjust and save. This can include turning on the Max button, adding a blur, and adjusting the Rf slider.

2.    When the alpha is to your liking, click the Make Modified Alpha button in the Alpha menu. This will create a new alpha in the palette that has the modifier settings “baked” in.

3. Select this new alpha and in the main Alpha menu click the Export button. This will save a copy of the currently selected alpha as the default PSD file type. Save the alpha in the ZStartup/Alphas folder if you want it to load by default each time ZBrush starts.

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 subfolder; 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 specific kind of surface texture that you cannot find 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 flat 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 fine 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 fill 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 canvas 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

If you had used ZAdd instead of ZSub, the alpha would be white on black. This is important to note. If you had used a combination of both ZAdd and ZSub, ZBrush would record the depth of the plane as 50% gray. This is because it’s compensating for pushing out as well as in. This is an acceptable way of making an alpha. However, you will have to use a radial fade; otherwise each alpha stroke will have a visible border when used on a model. You can remedy this by adding a radial fade with the Rf slider under the main Alpha menu.

5.    The canvas snapshot is now loaded in the Alpha palette. Since it captures black strokes on white (ZBrush sees subtraction as shades of gray beneath 50% gray), you need to invert the alpha. Under the main Alpha menu, click the Invr button. We’ll now reapply it to the canvas. Undo your previous strokes or create a new Plane3D so you have a clean surface on which to sculpt.

6.    With the Standard brush selected, pick the DragRect stroke and your new alpha. Click and drag on the plane surface to watch your alpha draw. As you now know, any surface texture that you can sculpt can be captured as an alpha. To save your custom alpha, from the main Alpha menu click the Export button. Save the alpha as a PSD file.