Adobe Photoshop CS4 - Manual (Page 599)

592 USING PHOTOSHOP CS4
3D and technical imaging
Last updated 1/10/2010
Create UV overlays
A diffuse texture file used by multiple materials on a 3D model can group several content areas that are applied to
different surfaces on the model. The process called UV mapping matches coordinates in the 2D texture map with
specific coordinates on the 3D model. UV mapping allows the 2D texture to be painted correctly onto the 3D model.
For 3D content created outside Photoshop, UV mapping occurs in the program where the content was created.
However, Photoshop can create UV overlays as guides to help you visualize how a 2D texture map matches up with
the 3D model surfaces. These overlays act as guides when editing a texture.
1 Double-click a texture in the Layers panel to open it for editing.
Note: Create UV Overlays is only enabled when a texture map is open and is the active window.
2 Choose 3D > Create UV Overlays, then select an overlay option.
Wireframe Shows edge data of the UV mapping.
Shaded Shows model areas using a solid rendering mode.
Normal Map Shows geometric normals translated to RGB values, where R=X, G=Y, and B=Z.
UV overlays are added as additional layers in the Layers panel for the texture file. You can show, hide, move, or delete
a UV overlay. The overlays appear on the model surface when you close and save the texture file, or switch from the
texture file to the associated 3D layer (the texture file is auto saved).
Note: Delete or hide UV overlays before performing a final render.
Reparameterize a texture map
Occasionally you may open a 3D model whose textures are poorly mapped to the underlying model mesh. Poor texture
mapping can produce obvious distortions in the surface appearance of the model, such as unwanted seams or areas of
stretching or squeezing of the texture pattern. Poor texture mapping can also cause unpredictable results when you
paint directly on the model.
To check texture parameterization, open a texture for editing, then apply a UV Overlay to see how the texture aligns
with the model surfaces. See “
Create UV overlays ” on page 592.
The Reparameterization command remaps a texture to the model to correct distortion and create more effective
surface coverage.
1 Open a 3D file with a poorly mapped diffuse texture, and select the 3D layer containing the model.
2 Choose 3D > Reparameterize. Photoshop notifies you that you are reapplying the texture to the model. Click OK.
3 Choose a reparameterization option:
• Low Distortion keeps the texture pattern more intact, but can create more seams on the model surface.
• Fewer Seams minimizes the number of seams that appear on the model. This can produce more stretching or
pinching of the texture, depending on the model.