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The Update section enables you to set how the IK solution is updated with Precise, Fast, and Manual options. The Precise option solves for every frame, Fast solves for only the current frame, and Manual solves only when the Update button is clicked. The Display Joints options determine whether joints are Always displayed or only When Selected.

When you first create a bones system, an end effector is set to the last joint automatically. In the End Effectors section, at the bottom of the IK Controller Parameters rollout, you can set any joint to be a Positional or Rotational end effector. To make a bone an end effector, select the bone and click the Create button. If the bone is already an end effector, then the Delete button is active. You also can link the bone to another parent object outside of the linkage with the Link button. The linked object then inherits the transformations of this new parent.

Click the Delete Joint button in the Remove IK section to delete a joint. If a bone is set to be an end effector, the Position or Rotation button displays the Key Info parameters for the selected bone.

Tutorial: Animating a spyglass with the HD IK solver

A telescoping spyglass is a good example of a kinematics system that you can use to show off the HD solver. The modeling of this example is easy because it consists of a bunch of cylinders that gradually get smaller.

To animate a spyglass with the HD IK solver, follow these steps:

1. Open the Spyglass.max file from the Chap 38 directory on the CD.

This file includes a simple spyglass made from primitive objects. The pieces of the spyglass are linked from the smallest section to the largest section. At the end of the spyglass is a dummy object linked to the last tube object.

2. To define the joint properties, select the largest tube object, open the Hierarchy panel, and click the IK button. In the Object Parameters rollout, select the Terminator, Bind Position, and Bind Orientation options to keep this joint from moving.

3. With the largest tube section selected, make the Z Axis option active in the Sliding Joints rollout, and disable all the axes in the Rotational Joints rollout. Click the Copy button for both Sliding Joints and Rotational Joints in the Object Properties rollout.

4. Select each remaining tube object individually, and click the Paste buttons for both the Sliding Joints and Rotational Joints.

This enables the local Z-axis sliding motion for all tube objects.

5. Select the largest tube section again, and choose Animation⇒IK Solvers⇒HD Solver. Then drag the dotted line to the dummy object at the end of the spyglass.

6. Select the second largest tube object, and for the Sliding Joint Z Axis, select the Limited option with values from 0.0 to –80. Click the Copy button for the Sliding Joints in the Object Parameters rollout. Select tubes 3 through 6 individually, and click the Paste button for the Sliding Joints to apply these same limits to the other tube objects.

7. Click the Auto Key button (or press N), drag the Time Slider to frame 100 (or press End), select the Select and Move button on the main toolbar (or press W), and drag the dummy object away from the largest tube object.

Figure 38.15 shows the end tube segment collapsing within the spyglass.

FIGURE 38.15

The HD IK solver is used to control the spyglass.

IK Limb solver

The IK Limb solver was specifically created to work with limbs. It is used on chains of three bones such as a hip, upper leg, and lower leg. Only two of the bones in the chain actually move. The goal for these three joints is located at the pivot point for the third bone. This solver is ideal for game character rigging.

This solver works by considering the first joint as a spherical joint that can rotate along three different axes, such as a hip or shoulder joint. The second joint can bend only in one direction, such as an elbow or knee joint.

The rollouts and controls for the