Tool:Texture Subpalette
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UV Mapping Methods
Very briefly, let’s discuss what UV Mapping is by using an example of an orange. If you were to make a 3D model of an orange, the geometry would be a simple sphere. Wrapped around this sphere is its peel—a 2D image that contains its color and even bump information. However, if you have ever peeled an orange and tried to lay it out flat, you know that it just doesn’t work. The peel stretches and breaks. The larger you try to make the pieces, the worse the stretching becomes.
This is exactly the same problem encountered by mapmakers when they try to unwrap the surface of the earth to put it onto a flat plane suitable for putting into a book. As a result, we end up with Mercator and many other kinds of projections, projections where slices are made through oceans (because that's where the least detail is), and other such techniques.
In 3D graphics, UV Mapping takes points on the surface of a 3D object and assigns (maps) them to corresponding points on a 2D plane (the texture). In order to overcome the problems inherent in unwrapping a 3D surface onto a 2D plane, various methods of mapping have been created. Each has its own strengths and weaknesses, and each is ideal for a particular model or use.
ZBrush utilizes the following methods, which can be assigned before you begin texturing by using the Tool:Texture subpalette.
Adaptive UV Tiles
A texturing method unique to ZBrush, this mapping technique produces the lowest possible amount of texture distortion. Every polygon in the model is assigned a separate square within the texture, in effect breaking the surface down into the smallest possible pieces.
When using this method, it's essential that the texture's width and height be 256 pixels or higher, and be a power of 2. For example: 1024x1024, 512x2048, etc.
If the AUV Ratio slider is set to 1 (which it is by default), each polygon receives an equal-sized portion of the texture. If the AUV Ratio slider is set higher than 1, larger polygons receive larger portions of the texture space. This technique helps to prevent distortions caused by variations in polygon size, and particularly for models where some polygons are much larger than others, you will likely want to set the AUV Ration higher than one.
On the other hand, when the AUV Ratio slider is set to 1, the same texture can be used on multiple deformations of the same model (because changes in the size of the polygons will not affect the areas of the texture map they correspond to).
Adaptive UV Tiles (with AUV Ratio set to 1) is the default mapping method applied to any skinned object, including those created with ZSpheres.
The textures created by Adaptive UV Tiles are indecipherable to the human eye. If you plan to use the texture in another application, most programs can use it without difficulty, but it’s a good idea to test first. In the other application, run a test with Mip-Mapping and Texture Antialiasing turned off. If the texture renders correctly, that application can make use of the Adaptive UV Tiles mapping method. If your model appears to have a grid of faint lines on it, then the application does not support this method.
AUVTiles may encounter difficulty mapping very high-resolution textures (1024 pixels or higher) to very low-polygon models (32 polys or lower). If this happens, do one of the following: Clone the texture with smaller Width and Height settings (256x256 or 512x512); press the Tool:Geometry:Divide button to increase the number of polygons; or choose a different mapping method.
Group UV Tiles
Group UV Tiles attempts to keep your UVs close to each other based on surface proximity and continuity.
To the right is a picture of the difference between GUV and AUV.
Other Types of UV Mapping
Other software can assign UV coordinates in a variety of other ways; even combining mapping methods on a single object. ZBrush respects these imported texture maps, and enables you to use any of its texturing methods (including the use of Projection Master) to generate, modify and refine textures.
These textures can be used to further incorporate the object in ZBrush artwork, and when exported, the same mapping method is applied.
Which to Use?
Use your best judgment to decide which method will work best for any given object. For ZBrush-generated objects, Adaptive UV Tiles is usually best. For use with imported objects, it may be best to stay with the texture-mapping method assigned outside of ZBrush. Only the simplest of objects work well with the other methods (such as Spherical for an eyeball).
Other Points
- 3D object textures must be loaded separately from the object. After the object has been imported, press Texture:Import load the desired texture.
- Depending on the file format, some texture maps may import upside down. Simply press Flip V in the Texture palette to invert them.
- Remember, when creating your own textures or modifying existing ones, texturing is far superior to vertex shading.
Controls
Colorize: Fills every polygon with the selected color.
Grd (Gradient): Blends colors between adjacent polygons.
Txr>Col: Uses the existing texture to colorize the mesh directly. No texture map is needed with a mesh of this type. Each polygon is assigned a color.
Col>Txr: Creates a texture map based on the current coloring of the object.
AUVTiles: Changes current UV mapping to Adaptive UVTiles. This form of UV Mapping unwraps every polygon separately onto the texture map. The result is a texture that is unintelligible to the naked eye, but is ideal for use with a 3D texturing program such as ZBrush's TextureMaster. Textures created with this method have less distortion than any other UV mapping technique.
GUVTiles: Changes the current UV mapping to one that organizes the UV coordinates by groups, i.e. the texture map will have areas of the model that are grouped presented as contiguous areas on the texture map. This gives a map which can be inspected or operated on manually. The AUVRatio slider also affects maps generated using GUV tiling, causing larger areas on the mesh to be mapped to larger areas on the texture map.
AUVRatio: If the AUV Ratio slider is set to 1 (which it is by default), each polygon receives an equal-sized portion of the texture. If the AUV Ratio slider is set higher than 1, larger polygons receive larger portions of the texture space. This technique helps to prevent distortions caused by variations in polygon size. See the section describing the Texture Palette for more information on Adaptive UV Tiling. Available only for polymesh objects.
UVTile: Changes current UV mapping to Tiles. Maps multiple copies of the currently selected texture to the object by assigning the same image to every polygon.
Uvc: Changes current UV mapping to cylindrical.
Uvp: Changes current UV mapping to planar.
Uvs: Changes current UV mapping to spherical.
HRepeat/VRepeat: Sets the number of times that the texture will be repeated on the object in the horizontal or vertical direction. Range = 1 to 32. Default = 1.
AdjU/AdjV/ApplyAdj: Adjusts the UV coordinates of the model by a small amount horizontally or vertically. Use this to fine tune texture’s fit when used in another application. Changes to the sliders will not take effect until ApplyAdj is pressed or the model is exported with a texture applied to it.
FSBorder: Sets the width adjustment for the next Fix Seam operation.
Fix Seam: Redraws the edges of disconnected polygons so background artifacts/seams are removed. This is performed automatically when a model is exported with a texture applied to it.
