Animation menu Constraints LookAt
The LookAt constraint
controls an object’s orientation so that it’s always looking at
another object. It locks an object’s rotation so that one of its
axes points toward the target object. The LookAt axis points toward
the target, while the Upnode axis defines which axis points upward.
If the two coincide, a flipping behavior may result. This is similar
to pointing a target camera straight up.
enable the antenna dishes to track the satellite.
An example of a LookAt
constraint’s use would be to constrain the eyeballs of a character
to a point helper. The eyes will then always be aimed at the point
helper. Animate the point helper, and the eyes follow. Even if you
rotate the character’s head, the eyes maintain their lock on the
Multiple Targets and Weighting
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
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 LookAt
constraint, you can access its properties on the LookAt Constraint
rollout on the Motion panel. On this rollout, you can add or delete
targets, assign weighting, assign and animate target weight values,
and adjust other related parameters.
NoteWhen you assign a
LookAt constraint via the Animation menu, 3ds Max assigns a Rotation
List controller to your object. In the list on the Rotation List
rollout, you will find LookAt Constraint, which is the constraint
you assigned. To view the LookAt Constraint rollout, double-click
the LookAt Constraint entry in the list.
- Add LookAt Target
Use to add new targets that
influence the constrained object.
- Delete LookAt Target
Use to remove target objects
that influence the constrained object.
Use to assign and animate
weight values for each target. Available only when multiple targets
- Keep Initial Offset
Maintains the constrained
object’s original orientation as an offset to its constrained orientation.
- Viewline Length
Defines the length of
the main viewline drawn from the pivot of the constrained object
to the pivot of its target (or the average, in case of multiple
targets). A negative value draws the line from the constrained object
in the opposite direction of the target or targets.
With a single target,
the length of the viewline is determined by the distance between the
constrained object and the target, as well as the Viewline Length
setting. However, if Viewline Length Absolute is on, the distance between
the two has no effect on the length.
The color of the viewline
is defined by the Target Line element in the Gizmos category of
panel in the Customize
User Interface dialog.
NoteWhen multiple targets
are assigned, additional viewlines drawn from the constrained object
to each target object inherit the color of the respective targets.
If Viewline Length Absolute is on, the length of each target-specific line
is determined by its target's Weight setting and the Viewline Length
value. If Viewline Length Absolute is off, the length of each line
is determined by the distance between the constrained object and
the respective target, as well as the Viewline Length value. An
additional (main) viewline, whose length and color are determined
as specified above, indicates the actual, calculated orientation.
- Viewline Length Absolute
When on, 3ds Max uses
only the Viewline Length setting for the length of the main viewline;
the distance between the constrained object and the target(s) has
- Set Orientation
Lets you define the offset orientation
of the constrained object manually. When 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
Sets the orientation
of the constrained object back to the default. This is useful if
you want to reset the constrained object’s orientation after having
set the orientation manually.
- Select LookAt Axis
Use to define the axis that
looks at the target. The X,Y,Z check boxes reflect the constrained
object's local coordinate system. The Flip check box reverses the directions
of the local axes.
- Select Upnode
The default Upnode is the
World. Turn off 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 LookAt Axis and the Upnode axis coincide,
the constrained object will flip. Animating the position of the
upnode object will move the upnode plane.
Upnode Control group:
Lets you quickly flip
between LookAt Upnode Control and Axis Alignment.
When selected the Upnode
matches the LookAt target.
- Axis Alignment
When this is selected
the Upnode Aligns to the object axis. Choose which axis (X, Y or
Z) in the Source Upnode Alignment group directly below Upnode Control.
- Source Axis
Chooses the constrained object’s
axis that is to be aligned to the Upnode Axis. The Source Axis reflects
the constrained object’s Local Axis. The Source Axis and LookAt Axis
work together therefore the Axis used to define the LookAt Axis
will be unavailable.
- Aligned to Upnode Axis
Chooses the Upnode axis that
the selected Source Axis aligns to. Note that the selected Source
axis may or may not be able to completely align to the Upnode Axis.