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.
LookAt constraints 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 point helper.
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 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 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
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
- 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 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 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 the Colors panel in the Customize 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
- 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 no effect.
- 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/Upnode Alignment group
- 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.