Look-At Constraint

A constrained object can be influenced by several target objects. When using multiple targets, each target has a weight value that defines the degree by which it influences the constrained object, relative to other targets.

Using Weight is meaningful (and available) only with multiple targets. A value of 0 means the target has no influence. Any value greater than 0 causes the target to influence the constrained object relative to other targets' Weight settings. For example, a target with a Weight value of 80 will have twice the influence of a target with a Weight value of 40.

Once you assign a Look-At constraint, you can access its properties on the Position Constraint rollout in the Motion panel. In this rollout you can add or delete targets, assign weighting, assign and animate target weight values, and adjust other, related parameters.

Note: When you assign a Look-At constraint via the Animation menu, the software assigns a Rotation List controller to your object. In the Rotation List rollout list you will find Look-At Constraint, which is the constraint you assigned. To view the look-at Constraint rollout, double-click look-at Constraint entry in the list.

Add look-at Target—Use to add new targets that influence the constrained object.

Delete look-at Target—Use to remove target objects that influence the constrained object.

Weight—Use to assign and animate weight values for each target. Available only when multiple targets are used.

Keep Initial Offset—Maintains the constrained object’s original orientation as an offset to its constrained orientation.

Viewline Length—Defines the length of the viewline drawn from the pivot of the constrained object to the pivot of its target. A negative value draws the line from the constrained object in the opposite direction of the target.

Note: The viewlines drawn from the constrained object to each target inherit the color of their respective target object. When multiple targets are assigned, another viewline indicates the actual, calculated orientation. The color of this line is defined by the Target Line element in the Gizmos category of the Colors panel in the Customize > Customize User Interface dialog.

Keep Viewline Length Absolute—When on, the Viewline Length setting is ignored and the viewline is always drawn between the constrained object and the target object.

Set Orientation—Use to manually define the offset orientation of the constrained object. When turned on, you can use the Rotation tool to set the constrained object’s orientation. This orientation is then maintained as the constrained object looks at its target.

Reset Orientation—Use to reset the orientation of the constrained object. This is useful if you want to reset the constrained object’s orientation after having set the orientation manually.

Select look-at Axis—Use to define the axis that looks at the target. The X,Y,Z check boxes reflect the constrained object's local axis. The Flip check box is used to flip the directions of the local axis.

Select Upnode—The default Upnode is the World. Uncheck world to manually select an object that defines the Upnode plane. This plane is drawn from the constrained object to the Upnode object. If the look at Axis and the Upnode axis coincide, the constrained object will flip. Animating the position of the upnode object will move the upnode plane.