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bottom beak is rotated open, the tongue goes with the beak more than it stays with the tongue joints. The interactive tubes were a little cumbersome in this area. We will paint the weights instead.

1. Select the Geometry.

2. Select Skin>Edit Smooth Skin>Paint Skin Weights Tool (option box). This opens the

painting weights window, much like what you have seen before.

3. If you right click on the tongue joint and in the hot box menu select the north-most box Select Influence then the joint will be selected and you can see the black and white representation

of its influence.

4. Using the Add operation and a value of 1, paint in the tongue areas of influence for each joint. 5. Using the hot key “ b ” and dragging from left to right resize the brush tool.

6. In the Paint Skin Weights tool box click on other joints to see what influence they have. The

bottom beak joint in mine has 100 percent ownership, too (it is all white when selected).

7. With the bottom beak joint selected, use the Replace operation and a value of 0, to paint out

the influence from the top beak. As you paint out the influence you will see the tongue geometry move to match the tongue joints.

8. Switch to the rotation tool and rotate the bottom beak to see that the tongue stays with the

tongue joints now. Remember to put all joints back to their preferred angle (assume preferred angle) or set their rotations to 0.

Let’s go over some problems in skinning and what to do about them:

1. Pokies: Where a vertex does not move with the area of geometry around it but moves with

some other joint—for example, the vertex in this wing. To fix this select the Vertex and choose under Skin>Edit Smooth Skin>Weight Hammer. There are no options to this tool. It sets the skin assignments based upon the neighboring weights. You can see it fixed the pokie in the wing. This option is also in the Paint Skin Weights Tool Box.

Figure 8.6 Painting skin weights on the tongue area.

2. Unwanted Jiggles: Often small numbers of movement will creep into the skinning and cause

jiggles. After most of the skinning has been done, select the Geometry and click on Skin>Edit

Smooth Skin>Prune Small Weight.

3. Wanted Jiggles: A great way to get a good look and feel of stretching skin is to add in just

the smallest of influence in fleshy areas. Say, for example, when the beak is open and closed, a small bit of skin around the eye should move slightly, too. To do this, select the bottom

beak joint and use the Smooth paint operation or the Add operation with a very small opacity and value. Paint in this “jiggle” around the bottom of the eye or anywhere where the

skin should stretch as the bottom beak opens.

4. Joints showing up in X-ray, even if the option is turned off. Although this isn’t a skinning

issue—it gets in the way. If your joints show up in X-ray mode even though it is turned off, simply turn on X-ray Joint mode and turn it off again. (The toggle is found under the viewport’s shading pull down.)

Figure 8.8 Adding jiggles.

5. Twisting or collapsing shoulder and wrist joints. What you have so far is a classic linear

skinning. When a shoulder or wrist or joint is rotated, the volume is not kept and the joint collapses. There have been many methods for dealing with this in the past. The newest is the introduction of dual quaternion skinning. What? Let’s take a look.

Select the lower leg and rotate it up. Let’s look at that joint to see what the different smooth bind skinning methods look like. First there is the classic linear skinning: see Figure 8.9. Find the skin cluster node and change the skinning method to Dual Quaternion; you’ll see the geometry around the joint gain a little volume: see Figure 8.9. The third option is weight blended. This option looks to a painted map that tells it which area should be Dual Quaternion and which area should be classic linear. Keep the option of weight blended.

Figure 8.9 Weight blended between classic linear and Dual Quaternion.

Return to the Paint Skin Weights Tool that you should be familiar with and this time switch the

Weight Type from Skin Weight to DQ Blend Weight. This is the map that indicates which area is

classic linear and which is Dual Quaternion. White (or 1)=full Dual Quaternion. Black (or 0)=classic linear. This will allow areas to be calculated to preserve volume and others to stay calculated as classic linear. I have not done bench testing here, but assume that full Dual Quaternion could slow the rig down. Test and make sure.

Figure 8.10 White (or 1) = full Dual Quaternion. Black (or 0) = classic linear.