CONSTRAINT

Rotation Limits

 

The Constraint->Rotation Limits command in the Actor and Motion modules sets a constraint on the range of rotation of one or more objects of a chain, such as restricting a head from rotating 360 degrees (unless this is what you want)! Global coordinates are always used for the constraint unless the object is parented, in which case the parent's coordinates are used.

A damping effect can also be set, adding resistance to the object's movement so that abrupt stops are avoided. Damping is apparent if the object has its rotation constrained in some way (such as with a rotation or direction constraint). For example, this allows the eyes of a character to follow a moving object and to damp when they reach a rotation limit. If you animate the eyes to rotate to the back of the head, damping and limit don't apply.

Damping can be applied on joints only for forward kinematics (rotations), but does not apply for inverse kinematics. In this case, only the crude limit can be applied.

 

Procedure

  1. Select the object to be constrained. You can only select one object at a time.
  2. Choose the Constraint->Rotation Limits command.

    The Rotation Limits dialogue box is displayed.

  3. Set the MIN and MAX rotation values for each axis by selecting a check box, and then typing the desired value into its corresponding text box.

    Note:

    Only the values for selected check boxes are applied to the constrained object.

  4. Set the Damping Width and Damping Strength.
  5. Click Ok to confirm the settings and exit the dialogue box.
  6. Select and rotate the constrained object as desired.

The constrained object never rotates beyond the minimum and maximum values set in the dialogue box.

 

Parameters

MIN and MAX Rotation Limits

Minimum and maximum values are expressed in degrees. They represent the object's range of rotation relative to the world or to a parent, if there is one.

For example, if the minimum and maximum values are set to -45 and 45 (degrees), the object can be rotated 45 degrees in either direction.

Damping

The Damping options set a degree of resistance to the movement of a constrained object as it approaches either end of its range of rotation. These options set the strength of the resistance and distance from the start of the range of rotation in which damping begins to take effect.

Damping Width

Sets the distance from either end of the object's range of rotation in which damping begins to take effect. The value is expressed in degrees.

For example, if the damping width is set to 10 (degrees), the damping effect begins to activate at 10 degrees from both ends of the object's rotation range.

Damping Strength

Sets the strength of the damping effect, with zero indicating no visible resistance to the rotation at either end of the range of rotation. The larger the value specified, the stiffer the damping.

In most cases, a value between 0.1 and 0.3 provides the most satisfactory results. A value of 1.0 is usually the maximum possible setting.

Default_Min and Default_Max

These two options provide a quick way to set the orientation limits. When you select either option, the rotation values that are currently displayed in the Rotation menu cells are automatically entered in the selected field. This is especially useful when you are setting limits on many joints at the same time.

 

Note:

When both Direction and Rotation Limits constraints have been applied to an object, colour feedback is provided. The dotted line that automatically appears when a Direction constraint has been activated changes according to the following:
- A blue line is the default colour, which means no orientation limit has been set.
- A pink line means that both orientation limits and damping have been set, and the object has been moved to where damping is activated.
- A red line means that both orientation limits and damping have been set, and the object has reached its maximum limit.

 

Last updated 03-apr-1998