Up Vector Cns

The Skeleton->Up Vector Cns command in the Actor module allows you to control the up direction (or y-axis) of a chain or an object that is already constrained to point toward another object (for example, a direction constraint). The up direction is controlled by using a secondary constraint object or null.

When applied to an inverse kinematic chain, the Up Vector constraint controls the general orientation of the chain. More precisely, it specifies the y-axis of the resolution plane. The x-axis of this plane is specified by the position of the effector relative to the root of the chain.

Note:

The general orientation of the chain changes rapidly when you move the effector into the region near the Up Vector constraint direction, causing the joint to flip.

For more information, see the Constraining Joints and Effectors section of the Animating User's Guide.

Procedure

1. Create an articulated chain using the Skeleton->Draw 2D Chain or Skeleton->Draw 3D Chain command.
2. Create a null.
3. Select the first joint of the chain.
4. Choose Skeleton->Up Vector Cns and pick the null. The null flashes red, and the constraint (dotted lines) appears. The dotted lines represent the resolution plane of the chain.

Note:

The Up Vector constraint has priority over the Preferred Axis constraint (see Skeleton->Preferred Axis Cns) when both constraints are applied to a chain.

Last updated 02-apr-1998