Painting Bump Maps
From ZBrush Info
A bump map is essentially a texture map which can easily be painted on your object in ZBrush using polypainting techniques. ZBrush 3.1 includes a bump viewer material which can preview the black, gray, and white strokes you paint on an object as differences in height (Previous versions of ZBrush included this material, however it needed to be loaded into the materials palette each time it was used in a session). The bump viewer material makes the strokes appear just like you would see them when the object is rendered in a 3D package with the same texture applied to the bump channel. It is important to note that the surface changes you see on the object are not changes in geometry. Bump maps are ideal for fine detail that is relatively flat such as pores on skin or very fine wrinkles. Follow these steps for a quick demonstration of how the bump viewer material works:
1. Draw a sphere object on the screen and switch to Edit mode (hotkey=t).
2. In the tool palette, convert the sphere to a polymesh by pressing the Make Polymesh3d button.
3. Subdivide the model a few times to increase the resolution.
4. In the Materials palette choose the BumpViewerMaterial at the lower corner of the Standard Materials Section.
5. Enable PolyPainting on the object by turning on the Colorize button in the Tool palette (Tool:Texture:Colorize). To see an example of PolyPainting check out the First Painting page.
6. Switch to the Standard Brush. Turn on the RGB button, turn off Zadd or Zsub.
7. Set the color picker to a dark gray and draw on the surface of the model. You should see a depression form. This is actually a preview of how the bump texture will deform the surface when exported applied to the bump channel of a shader and rendered (on the same model) in another 3d package.
8. Rotate the model so that the depression in on an edge that turns away from the camera, notice that the surface of the model is not actually deformed.
9. Switch the material to the Fast Shader material, you can now see how the texture will actually look when converted to a texture and exported from ZBrush.
10. To raise the surface set the color picker to light gray or white and continue painting. You can match the depth of previous strokes by dragging from the color picker to painted strokes on the model in the same way that you sample colors from any other colored surface.
11. When you are satisfied with your bump map you can convert it to an exportable texture by first creating a texture (Texture:New), and then clicking on the Col>Txr button (Tools:Texture:Col>Txr). You must set a resolution before creating the texture, also note that your painted strokes will disappear when you click on the New button in the Texture menu, don't panic, the strokes still exist and will reappear when you convert the color to a texture. For more detailed information on converting the colors painted on the polygon model to an exportable texture consult the polypainting page.
12. Try using other brushes to create the bump map, just make sure that RGB is on and Zadd, Zsub, and Zcut are off. Experiment with different alphas as well.
To Learn About Bump Maps Click Here.
