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This chapter is from the book

This chapter is from the book

Hooking Up the Head Skeletal Hierarchy

For the head of a character, you can create a separate hierarchy that is point-constrained to a locator that is a child of the spine or neck. This leaves the rotational controls free from the hierarchy and enables the animator to animate them by hand (see Figure 17.62). You will do this in the next exercise.

Figure 17.62Figure 17.62 IK layout for the head.

Exercise 17.10 Attaching the Head Setup

This is a short exercise that goes through a few simple steps to create a joint hierarchy for the head. The head is created first. Then it is connected to the neck using a combination of constraints that allow for additional freedom when animation occurs, giving the character's head extra flexibility later.

  1. Create the head joints for your character using a similar joint layout as shown in Figure 17.62.

  2. It is a good idea to place the jaw's point of rotation slightly in front of and below the side view of the ear lobe. Usually you should include a few extra joints that stem from the jaw, as well as a joint that goes up to the top of the head of your character, for extra weighting of the facial geometry.

  3. Next, create a locator and point-snap it to the root of the head skeleton that you just created. Make this locator a child of the nearest neck joint.

  4. Point-constrain the head's root to this new child locator by selecting the locator and then the head's root joint, and performing Constrain, Point (see Figure 17.63).

  5. This setup allows the character's head to rotate freely from the spine and neck, but it still translates around with the neck and spine appropriately. If you need to translate the neck by any small amount, the ability is there by moving the locator that the head is constrained onto.

    Figure 17.63Figure 17.63 Full head setup with control boxes.

Facial Controls and Blend Shape Deformers

Although facial rigging was a smaller portion of the setup for this project, the way that the rigging was accomplished can also be used for complex scenarios of lip-synching and high-range emotional facial animation. All facial expression controls can be successfully implemented in a very traditional way. You first model them as separate models and apply them as blend shapes targets. Then you rig each attribute of your blend shape into a single faceController node simply and quickly by adding attributes. Then you use the Connection Editor to quickly hook them all into the single faceController node so that they are easily accessible to the animator.

Eye blinks can also be modeled as blend shapes and hooked up using set-driven key onto attributes of a driver. Each eye should have a separate blink control so that the eyes can blink at an offset of each other (see Figure 17.64).

Figure 17.64Figure 17.64 Blend shape setup for eye blinks.

The opening and closing of the jaw can be achieved using joints and painting the smooth bind weights to achieve an appropriate and appealing opening and closing of the mouth corners.

It is important to note that all the blend shapes for the lips must be modeled with the geometry in the default pose, with the mouth closed, to avoid double transformations of the jaw being double deformed while opening.

TIP

To create blend shapes for a character that has already been bound to a skeleton, you will want to be sure of two things:

Be sure that you are using an exact duplicate of the character's geometry before it was bound to the skeleton to begin modeling your blend shapes.

When you create the blend shape, go into the Advanced tab in the Create Blend Shape options box and choose the Front of Chain options in the deformation order pull-down menu. Or, after you create the blend shape, choose Inputs, All Inputs and use the middle mouse button to drag your blend shape to the bottom of the deformation order list (just above any tweak nodes there—see Figure 17.65).

Figure 17.65Figure 17.65 List of history operations window.

Creating Eye Controls

The eye's "look at" controls were set up simply with two joints for each eye. RPK IK handles were point- and pole vector–constrained to a locator that is a child of the "look at" control.

The next exercise takes you through this process. Start with a new scene and create two spheres, evenly placed as your eyeball objects.

Exercise 17.11 Eye Setup

Begin by creating the joints for the eyes.

  1. Create two joints for each eye.

  2. The crucial aspect of where these joints get placed is that the parent joint (the one that will control the rotations of the eye) has its location in the exact same location of the eye geometry's pivot. Therefore, it is also extremely important that the eye be capable of rotating around its own pivot without visibly intersecting any of the face's external geometry. In other words, make sure the eyes can look around correctly by simply rotating around. If the eyes are perfect spheres and are carefully placed inside the head, and if the head is modeled correctly around the eyes, centering the pivot of the eyes should work just fine.

    An easy way to make sure your parent joint is in the exact same place as your eyeball joint is to turn on handles for the node that should rotate the eyes. You can do this by selecting the joint and going to Display, Component Display, Selection Handles. Then use the v key to point-snap the joint directly on top of the location during creation and layout of the joint.

  3. Create two locators, and place each locator directly in front of each eye.

  4. Name the joints and the two children locators appropriately according to which eye they are in front of: leftEyeJoints and leftEyeAim.

  5. Next, create an IK handle from the parent joint to the end joint at the end of the eye.

  6. Now select the "look at" locator first and the IK handle second; click Constrain, Point to point-constrain the IK handle onto the locator.

  7. With the same selection active, click Constrain, Pole Vector to pole vector– constrain the IK handle to the same target.

  8. Select the eyeball geometry group. Shift+select the parent eyeball joint, and hit p to parent the eyeball geometry to the joint (see Figure 17.66).

  9. Figure 17.66Figure 17.66 Parenting the eyeball to the eyeball joint hierarchy.

You can now hook up some parented control boxes to make the eyes look around. You can add an additional parent to the aim locator that is point-constrained to the location of the eyes. An animator can use this to have FK-style rotations and then actually translate the locator to have the IK style look at control as well.

This technique involves several really cool things. First, you will not get flipping because you will have control over the IK handle's rotate plane much better than a mere aim constrain could provide. Second, you can actually bind those joints that are rotating the eyes to the face geometry. When you weight the character, you will want to carefully distribute the weighting of the eye joints just around the lids of the character, somewhere between .2 and .4, so that the fleshy area around the eyes actually deforms subtlety enough when his eyes look around.

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