Add target objects for target constraints

After you’ve created a tangent constraint, you can add more target objects for additional control over the constrained object’s orientation. Adding more target objects is similar to creating tangent constraints.

To add target objects for target constraints

1. Select one or more objects you want to add as target objects, followed by the constrained object.
2. Select Constrain > Tangent > .
3. Click Add to add the selected objects as target objects.

Remove target objects for tangent constraints

After you’ve created a tangent constraint, you can remove any of the target objects so that the objects no longer constrain the constrained object. Removing target objects is similar to adding target objects.

To remove target objects

1. Select one or more objects you want to remove as target objects, followed by the constrained object.
2. Select Constraint > Remove Target.

Note that when you remove a target object, you also remove any animation curves attached to the constraint object for that target object.

You can also remove specific axes from a constraint. For this procedure, see Remove a target object.

Change target object weights for tangent constraints

A target object’s weight specifies how much the orientation of the constrained object can be influenced by a target object. The weights are attributes of the tangent constraint. For each target object, an attribute named targetObject Wn is included that specifies the weight of each target object. By default, the weights are set to 1, which gives each target object an equal influence over the constrained object’s orientation. However, you can change the weights so that some target objects can have more (or less) influence than others. You can change target object weights with the Channel Box or the Attribute Editor.

To change target object weights for tangent constraints with the Channel Box

1. Edit the targetObject Wn channels as described in Edit tangent constraint channels.

To change target object weights for tangent constraints with the Attribute Editor

1. Edit the targetObject Wn attributes as described in Edit tangent constraint attributes.

Prevent rolling effects for tangent constraints

In certain situations, a constrained object can rapidly roll about its aim vector. Rolling effects can happen when the aim vector approaches or points in the same direction or in the opposite direction as the up vector. For more information, see Rolling effects.

You can avoid rolling effects by keeping the target vector clear of the world up vector’s direction. For example, if the world up vector points in the direction of the scene’s world space Y-axis (the default), you would try to avoid having the positive or negative Y-axis point in the same direction as the target vector. You could move the target object(s) as needed, or perhaps change the target object weights so that the target vector does not get to close to the Y-axis.

However, if your animation makes such avoidances impossible, you can prevent rolling by changing or animating the world up vector.

To change world up vector for tangent constraints with the Attribute Editor

1. Edit the World Up Vector attribute as described in Edit tangent constraint attributes. Note that you can also use the Channel Box to edit the World Up Vector.

To animate the world up vector for tangent constraints with Channel Box

1. You can set keys on the World Up Vector attribute by using the Channel Box. To select the World Up Vector attribute, see Edit tangent constraint channels. To set keys on the World Up Vector, select the World Up Vector channel, -click it, and select Key Selected from the pop-up menu that appears.

Control motion history dependence effects for tangent constraints

In certain situations, a constrained object can become motion history dependent. For more information, see Motion history dependence effects.

You can control motion history dependence by making sure that the aim vector and the up vector do not point in the same direction. If they are pointing in the same direction, the best way to prevent motion history dependence is to change the up vector’s direction. You could also change the aim vector, but it’s likely that you choose the aim vector so that the object aims in a particular way.

Additionally, if the tangent constraint’s World Up Type is set to None, the constrained object can be motion history dependent.

To change up vector or aim vector direction for tangent constraints with the Attribute Editor

1. Check the Aim Vector and Up Vector attributes as described in Edit tangent constraint attributes. If they are the same, edit one of the them so that they do not both point in the same direction.

To change the World Up Type attribute for tangent constraints with the Attribute Editor

1. Check the World Up Type attribute as described in Edit tangent constraint attributes. If set to None, the constrained object can be motion history dependent.