Unfolding with constraints

Sometimes you only need to unfold a UV mesh in one direction. This is especially useful when there is only a single seam.

To unfold the arms

1. Select the soldier’s left arm.
2. Select Create UVs > Planar Mapping.
3. -click the arm and select Assign Existing Material > checker_pattern.
   
4. -click the arm and select Edge from the marking menu.
5. Select the edges on the bottom of the arm at the center of the distortion just under the elbow.
   
6. In the UV Texture Editor, select Polygons > Cut UV Edges.
7. -click the arm and select UV from the marking menu.
8. Drag-select all the UVs on the arm and click the Rotate clockwise button ().

   The UVs rotate so the arm in the UV Texture Editor is vertical.

   
9. -select one UV at the top of the arm’s bicep and another UV at the tip of the soldier’s cuff.
   
10. Select Polygons > Unfold > .

    The Unfold UVs Options window appears.

11. Set Unfold constraint to Horizontal.
12. Click Apply and Close.

The UV mesh for the arm is unfolded evenly up and down. This is better than the UV mesh we would get if we unfolded in all directions.

Now you can output these UVs to a file.

To export the UV snapshot

1. -click the arm in the UV Texture Editor and select UV from the marking menu.
2. Drag-select all the UVs on the UV mesh.
3. Select the Scale Tool.
4. In the UV Texture Editor, scale the UV mesh so that it fits inside the upper-right square of the UV Texture Editor.

   This step is necessary because a UV snapshot only captures what is in the 1 x 1 UV texture space (the upper right corner).

5. -click the arm in the perspective view and select Object Mode.
6. Select the arm.
7. In the UV Texture Editor, select Polygons > UV Snapshot.

   The UV Snapshot options window appears.

8. Click the Browse button.

   A file browser appears.

9. Navigate to GettingStartedMaya2013LessonData\UVMapping and enter the name left_arm_UVs.
10. Click Save.
11. Set Image Format to Maya IFF.
12. Click OK.

    Like the torso you did in the previous step, Maya outputs an .iff file containing the UV mesh. You can import this file into an image editor and use it as a template to create a texture.

Now repeat the entire procedure for the right arm. Note that you do not need to output the UVs for the right arm because it will use the same texture as the left arm.

Although you could handle the legs the same way you handled the arms (cutting them into two pieces), you can also treat the entire lower body as a single mesh. You can follow the same procedure as above, except for the following:

• Select the edges down the rear until directly underneath the groin then select the edges on the inside of each leg. Cut these UV edges.
  
• You do not need to pin any UVs for the pants (but you must select the pants as an object to unfold the UVs). Also, remember to turn off Pins UVs in the Unfold UVs Options window.
• Like the arms, unfold the UV mesh horizontaly.

As with the torso and arms, you can now output these UV meshes to an external file to paint a texture on them. For information about how to do this, see Outputting UVs.