All images from Poser 7 Revealed: The e frontier Official Guide by Kelly L. Murdock.

This is the next in a new series of excerpts from the Thomson Course Technology book Poser 7 Revealed: The e frontier Official Guide. In the next few months, VFXWorld readers will develop the skills needed to create, render and animate scenes and projects using the amazing tools offered by Poser 7. We will offer step-by-step tutorials for each task, followed by projects that allow readers to apply each new skill.

What You'll Do
In this lesson, you learn how to create a new IK chain.

Kinematics is the physics behind the movement of linked objects. Bone structures are a good example of a set of linked objects that can be defined using kinematic solutions. For example, because the shoulder is connected to the arm bones, which are connected to the hand, you can use kinematic equations to determine the position of the hand as the shoulder moves. Inverse Kinematics works backwards by solving the shoulder's position as the hand is moved.

The benefit of Inverse Kinematics is that it is often easier to animate characters by placing their hands and feet than placing their hips and shoulders. For example, imagine a character walking across the floor and reaching for a door handle. To animate this sequence by moving only the upper thigh and upper arm bones would be difficult, but with Inverse Kinematics enabled, you can position the feet for the steps and the hand for the door handle and the remaining body parts just follow.

[Figure 1] Hierarchy Editor (left). [Figure 2] IK chains in the Hierarchy Editor (right). 

Working with Inverse Kinematics
When Poser first loads, select the default figure's Left Thigh object and try to move it with the Translate/Pull tool. The upper thigh element might twist a little, but because it is part of the IK chain, it won't move out of place unless the end of the IK chain, the foot, is moved.

Now try disabling IK and moving the upper thigh element again. This time the upper thigh moves easily and the foot moves along with it. The trick is to learn when to use IK and when to disable it.

In order for Inverse Kinematics to work, you need to select a parent object (the root object) and one of its children objects (the goal object) connected in a chain. All the bones between these two selected bones are collectively called an IK chain. You can select IK chains by using the Hierarchy Editor. This dialog box is opened with the Window, Hierarchy Editor menu command. All IK chains for the current figure are displayed at the bottom of the Hierarchy Editor, shown in Figure 1.