Inverse Kinematics

This tool enables you to move hierarchical objects interactively using inverse kinematics (IK). For example, you can grab the hand of an arm and move it to the required position. The arm will follow automatically, obeying any rotation restrictions you have applied to the joints.

Not only is the IK tool useful for animation, it’s also ideal for posing characters. You will need to arrange the objects into a hierarchy and assign Inverse Kinematic tags.

If you select an object at the end of a hierarchy and move the mouse, CINEMA 4D calculates the distance between the joints automatically and keeps it constant.

CINEMA 4D’s Figure object is superb for learning IK. To see its Anchor and Kinematic tags, make the figure editable (Functions > Make Editable).

This prevents the chain (e.g. an arm with several joints) from pulling apart.

CINEMA 4D’s Figure object is mainly included in CINEMA 4D to help you learn how to set up an IK figure. To create the Figure object, choose Objects > Primitive > Figure. Next, select Functions > Make Editable — this converts the figure into polygons with separate limbs, an existing hierarchy and all the tags you need to get started. To use IK, select the IK tool and the Move tool, click a body part such as a hand, then drag within the viewport. Study the IK and Anchor tags and experiment with their settings.

When setting up an IK chain, you can specify angle constraints to prevent limbs moving beyond certain angles using the Kinematic tag.

You can also define objects to be anchors using the Anchor tag. These objects cannot be moved using the Inverse Kinematics tool.

The IK tool always applies to the selected object. The IK chain is pulled from the object’s origin or, if the object has child objects, from the origin of the first child.