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Skin weighting and deformations

Lesson 2: Smooth skinning

Influence objects

 

Learning Resources > Tutorials > Getting Started with Maya > Character Setup > Lesson 2: Smooth skinning > 

Modifying skin weights

You can modify the skin weights for any of the influencing joints to alter the irregular region. If you don’t get the desired results when you change the skin weights of one of the influencing joints, you can undo your changes and try another influencing joint.

In general, it’s best to modify the skin weights of the most influential joint first, then work with less influential joints if you don’t get the desired results. Modifying skin weights requires experimentation.

In the next steps, you’ll modify the skin weights for the left_arm_root joint.

To modify skin weights using the Paint Skin Weights Tool

1. Select left_arm_root in the Influence list.
2. In the Paint Weights Menu section of the window, set Value to 0.1 and turn on Add.
3. Drag the mouse pointer to paint the irregular region of the breast. Each stroke adds 0.1 (10%) to the skin weight. The weight for a skin point has a maximum value of 1 (fully white).
   TipPainting skin weights using a tablet with stylus allows you to take advantage of pressure sensitivity.

   Repeat the strokes several times until the irregular region becomes smoother. The jagged, asymmetrical wireframe at the breast becomes more symmetrical as the skin becomes smoother. The region whitens, which indicates increased influence from the left_arm_root joint. Note that increasing the influence of one joint lessens the influence of the other influencing joints.

4. To check the shape with full-color shading, click the Select Tool. (You might also prefer to cancel the selection of Jackie to eliminate the display of the highlighted wireframe.)

   

5. To continue modifying the skin weights with the Paint Skin Weights Tool, select Jackie and once again select Skin > Edit Smooth Skin > Paint Skin Weights Tool.

   There are several additional tool settings you might find useful as you modify skin weights:

   • The Smooth operation smooths the weights of points by averaging the stroked points with the weights of the surrounding region. This is useful if you add to the weight values in some region but the points become unevenly weighted. Uneven weights are indicated by mottled gray skin.
   • You can use the Scale operation with a Value less than 1 to scale down the point weights of a stroked region.
   • As you stroke a region, the red circle icon displays the radius of the region affected by the stroke. The Radius(U) value changes the radius.
   • You can select any of the Profile icons to specify the region affected by strokes. The two leftmost icons are the most commonly used shapes.
6. (Optional) If you want more practice, pose the right arm as you posed the left arm and fix the corresponding irregular region in the right breast. This time, fix the region by modifying the weights for the upper_back joint rather than the right_arm_root. As mentioned previously, you can modify point weights of alternative joints to get a similar effect.
7. After you eliminate the irregular region from the left breast, move the arm to different positions to see if the breast’s shape stays natural in various poses. It is common for a surface to look good in one pose but not in another. Strive to make the surface look good in the poses that you are likely to use during animation.