3ds Max 2012 Bible - Kelly L. Murdock [414]
The first rollout, after the Assign Controller rollout, is the IK Solver rollout, shown in Figure 38.11. Using this rollout, you can select to switch between the HI IK solver and the IK Limb solver. The Enabled button lets you disable the solver. By disabling the solver, you can use forward kinematics to move the objects. To return to the IK solution, simply click the Enabled button again. The IK for FK Pose option enables IK control even if the IK solver is disabled. This lets you manipulate the hierarchy of objects using forward kinematics while still working with the IK solution. If both the IK for FK Pose and the Enabled buttons are disabled, then the goal can move without affecting the hierarchy of objects.
FIGURE 38.11
The IK Solver rollout lets you enable or disable the IK solver.
If the goal ever gets moved away from the end link, clicking the IK/FK Snap button automatically moves the goal to match the end links position. Auto Snap automatically keeps the goal and the end link together. The Set as Preferred Angle button remembers the angles for the IK system. These angles can be recalled at any time using the Assume Preferred Angle button.
When you choose Animation⇒IK Solvers⇒HI Solver, the start joint is the selected object, and the end joint is the object to which you drag the dotted line. If you want to change these objects, you can click the Pick Start Joint or Pick End Joint buttons.
Tip
The best way to select an object using the Pick Start Joint and Pick End Joint buttons is to open the Select by Name dialog box by pressing the H key. Using this dialog box, you can select an exact object without missing selecting it in a complex viewport. •
Caution
If you select a child as the start joint and an object above the child as the end joint, then moving the goal has no effect on the IK chain. •
Defining a swivel angle
The IK Solver Properties rollout includes the Swivel Angle value. The swivel angle defines the plane that includes the joint objects and the line that connects the starting and ending joints. This plane is key because it defines the direction that the joint moves when bent.
The Swivel Angle value can change during an animation. Using the Pick Target button, you also can select a Target object to control the swivel angle. The Use button turns the target on and off. The Parent Space group defines whether the IK Goal's parent object or the Start Joint's parent object is used to define the plane. Having an option lets you select two different parent objects that control the swivel plane if two or more IK solvers are applied to a single IK chain.
You also can change the Swivel Angle value by using a manipulator. To view the manipulator, click the Select and Manipulate button on the main toolbar. This manipulator is a green line with a square on the end of it. Dragging this manipulator in the viewports causes the swivel angle to change.
To understand the swivel angle, consider the two puppet bones systems displayed in Figure 38.12. The HI solver has been applied to the right arms of both puppets with the upper arm as the beginning joint and the hand as the end joint. The swivel angle for the left bones system is 90 degrees, and the swivel angle for the right bones system is 180. You can see the manipulators for both bones systems. The left one is pointing upward, and the right one is pointing straight out from the puppet's head. Notice that the swivel angle determines the direction the elbow joint is pointing. The left bones system's elbow is pointing up and away from the spine, and the right bones system's elbow is pointing painfully out in front