Example: Lay out a UV shell using unfold and relax

You can use the Smooth UV Tool to relax or unfold an entire UV shell into the UV space. You can then use the same tool to fix small imperfections in the shell.

The following workflow provides the following benefits:

• It is easier to assign a texture to a square area.
• Ensures the texture is spread evenly.

To map a shell to the UV space

1. Create a mapping for your object by selecting Create UVs > Planar Mapping from the Polygons menu set.

   In this case, a planar projection from the front (the Z Axis) is appropriate. In other cases you must determine the best projection to start with.

2. Open the UV Texture Editor (Window > UV Texture Editor).
   
3. In the perspective view, select a path of edges along the back of the head starting at the top of the forehead and ending at the bottom of the neck.
4. In the UV Texture Editor, select Polygons > Cut UV Edges.
   
5. Select the central UV at the top of the forehead and in the UV Texture Editor, select Polygons > Unfold > .

   The Unfold Options window appears.

6. Turn on Pin UVs and Pin selected UVs.
7. Set the Unfold constraint to Horizontal.
8. Click Apply and Close.

   The UV shell unfolds relative to the selected UV on the forehead so that the previously cut edges are spread out horizontally.

   Note

   Rather than using the Unfold option, you can also use the Smooth UV Tool to unfold the entire UV shell. In this case, you would select all the UVs except for the one at the top of the forehead and then + drag the Unfold icon to the right.

9. Use the Scale Tool to scale the UV shell into the 0,1 texture space.
   
10. Select the edges on one side of the mesh.
11. Select Polygons > Straighten UV Border.

    The UV border straightens.

12. Repeat steps 10 and 11 for each side of the UV shell.
    
13. Turn on the Snap to grids option.
14. Select the Move Tool and move the border UVs to the edge of the 0,1 texture space.

    The Snap to grids option ensures that the UVs snap to the border precisely.

    
15. Select all the UVs.
16. Select Tool > Smooth UV Tool > .

    The Smooth UV Options window appears.

17. Turn on Pin Borders.

    This ensures that the UV border aren’t distorted.

18. Set Space to UV Space.
19. Click Apply and Close.

    Two controls named Unfold and Relax appear.

20. Drag the Relax control to the right.

    The entire UV shell, except for the borders, relaxes evenly.

    

With the Smooth UV Tool you can use your eye to judge how much the UV shell should relax. However, whether you use this method or the Relax option (Polygons > Relax), it is unlikely that the UV shell will be perfect.

If you turn on the Shaded UV Display, you can see small imperfections in your relaxed shell. For example, the UV shell around the eyes and corners of the mouth for this model cause the shell to overlap itself.

You can use the Smooth UV Tool to smooth out these problem areas.

To smooth imperfections in a relaxed shell

1. Select Tool > Smooth UV Tool > .

   The Smooth UV Options window appears.

2. Turn off Pin Borders and then select Apply and Close.
3. Select a set of UVs around the eye.
4. Drag the Unfold control to the right until the UV shell no longer overlaps itself.
   
5. Repeat for the mouth.
   
6. You can select smaller or larger sets of UVs and use the Smooth UV Tool in conjunction with the transformation tools to quickly clean up your UV shell.
   

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