Figure Five

While we could continue editing vertex weights one by one, this can clearly become a time consuming process as it was in PowerAnimator. Maya, however, offers some flexibility at this point. The next thing we can do to the leg is to add flexors. Flexors are created by selecting a joint and choosing Skinning/Create Flexor which will automatically open a dialogue box seen in Figure 5. (Note: It is important to make sure the skeleton is in its 'bind pose' before adding flexors). There are three types of flexors which can be added: Lattice, Sculpt and Joint Cluster. These can be added to either a joint or bone, where if a joint is selected, the bone which decends down from it would be the modified bone. A joint flexor is used for knees, elbows and so on, while a bone flexor is used for bicep, tricep, etc.


Figure Six

What happens when a JointCluster flexor is added is that the weights of the pre-existing clusters are modified (ie no new object is created) so that they fade through the joint. Figure 6 illustrates this as the weights of the vertices are no longer all at 1. The enveloping of where the fading begins and ends can be controlled by selecting the 'J' now visible at the joint and editing its attributes in the attribute editor.


Figure Seven

Sculpt flexors are no different than manually adding a Sculpt deformer to the geometry and then parenting this Sculpt to the joint. The technique to use when the Sculpt flexor is created is to use Set Driven key so that as the joints bend, the Sculpt flexor(s) becomes more pronounced by either transforming, scaling, rotating or changing strength and falloff. This can be very effective for elbows and kneecaps, where a few sculpts could be added to create the knee cap definition which appears as the knee bends as in Figure 7.


Figure Eight


Figure Nine

The last flexor is the lattice, where a new lattice is created around the selected joint or bone. When first created, the lattice may appear a bit oversized for the geometry, however, which is the reason for the 'position the flexor' option when creating a lattice flexor. When this option is checked, the lattice can be moved, rotated and scaled to better suit the geometry as in Figure 8. The nice thing about lattice flexors is that the equivalent of Set Driven Key is built in. When we bend the knee, for example, we can see that the lattice has already modified our deformation by smoothing out the affected area. But if we select the lattice, it?s unique attributes such as 'rounding' and 'creasing' will appear in the channel box for editing. If we modify these to interactively design the deformation as in Figure 9, when we straighten the leg back to it's 'bind pose', the flexor assumes its original, neutral, shape. We could, however, tweak the effect even more by layering some Set Driven Key relationships between the knee joint?s rotation and the actual position of the lattice flexor's points. A useful tip at this point is that if there are not enough divisions in the lattice flexor, it's unique attributes may not work. At least four divisions must exist in S,T and U for all rounding, creasing, etc to work.


Figure Ten


Figure Eleven

Once the clusters, vertex weights, and flexors have been added and tweaked, the next level of control which can be added is Blendshape. As shown in part one, Blendshape is a morphing tool which offers a high level of interactivity and flexibility. Figure 10 shows copies of each of the three surfaces which make up the leg moved over to the side. A lattice has been added to all three surfaces with enough divisions to have a decent amount of control over the surfaces. The choice of a lattice is so that we can avoid breaking our seams. Each of these three copies have also been set as Blendshape targets for the bound originals by using Deformations/Blendshape. While we still have yet to modify the copies, the Blendshape morph sliders for each surface has been moved up to one. At this point, if we modify the duplicates, the original bound geometry will deform. Thus we can use these Blendshape targets for a wide variety of deformation modifications. A very important note, however, is to change the order of deformations. Since we created the Blendshape targets after binding the leg geometry to the skeleton, the Blendshapes will be calculated after the clusters which are parented to the joints. What we want, however, is for them to be calulated first. Thus the leg geometry morphs and then is bent by the skeleton. Otherwise, the leg will bend and then slide back to its original straight position when the Blendshape is activated. The order of deformation is modified by selecting the affected geometry, clicking on the Inputs button on the Status line and choosing Complete list from the pull down menu. This will open a window which lists all the nodes which affect the geometry. By middle mouse button dragging one item to the position of another, their order will be modified. The item at the top of the list is calculated last. Figure 11 shows what type of effects can be achieved with this technique.


Figure Twelve


Figure Thirteen


Figure Fourteen

With the legs now set up, the same techniques are used for Lanker's arms and fingers. The regions which become a bit more tricky, however, are the pelvis, shoulder and knuckles. The reasons for this is that these regions contain more than one surface which can easily separate at the seams if care is not taken. When a deformation needs to occur in this type of situation, the easiest solution is to use lattices as they will maintai n the relationship between adjacent surfaces. However, it is important to make sure that any part of the surfaces which affect the seam in any way are included in this latttice. Figure 12 shows a lattice which has been added to the pelvic region, including the vertices of the torso below the waist, the blend surfaces which connect the pelvis to the legs, and the top two rows of vertices on each leg. It is also important to have enough divisions on this lattice so that the left and right hip joints can be associated with the respective halves of the lattice. At this point, we can now select the left hip joint, the left half of the lattice points and invoke Bindskin. This has now created a cluster of those points and parented it to the joint. Bending the leg at this point gives as an undesirable result, however, as seen in Figure 13. What we now must do is edit the weights of the lattice points in the cluster using the Set Editor, so that the lattice points at the middle and top edges have a weight of zero, and then fade up to one towards the center. After editing the weights a bit, a much smoother deformation can be achieved (Figure 14).