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Reaction Controllers 359
5.
On the Assign Controller rollout, click the
Assign C ontroller button.
6. On the Assign Position Controller dia log, click
P osition Reaction to highlight it, and then click
OK.
This opens the Reaction Manager dialog (page
2–361). T he Reactions list shows that the sphere
is assig ned as a slave, but no m aster is assigned.
A Reaction controller uses a master’s motion to
control any number of slaves.
7. Right-click the “Unassigned” line at the top
of the Reactions list. From the menu, choose
Replace Master .
This places you in a Pick mode where you can
choose a motion track from any object in the
scene to act as master.
8. In any viewport, click the box (Box01).
Apop-upmenuappears.
9. From the pop-up menu, choose Transform >
Position > X Position.
The “Unassig ned” text is replaced by a master
track labeled “B ox01 / X Position”.
Also,anewstate,State01,appearsintheStates
list.
This is an example of the basis of the control
mechanism used by the Reaction cont roller:
For each master/slave combination, you can
specify any number of states defined by values
for the m a ster and slave tracks. The first state,
created automatically when you added the
master, specifies that when the box is at -100 on
the X axis, the sphere should be at (-100,0,50).
In this case, you’re controlling three parameters
(the sphere position on a l l t hree axes) with one
(the box position on the X axis). More typical ly
you’d use one-to-one master/slave-parameter
ratios.
Note: Reaction Manager also defines a state
automatically when you assign a new slave to a
master.
Next you’ll create a second state that tells the
sphere how to move on multiple axes as the box
moves on one.
10. Movethetimeslidertoframe50.
The box mov es to the midpoint of its animated
trajectory. The sphere remains where it is.
11. On the React ion Manager dialog, click the
Create Sta te button.
This creates a new state (State02) using the
current positions of the box and sphere.
12. Try moving the sphere in the Front view port.
You can’t move the sphere because it’s under the
full control of its master, the box. Similarly, you
can’t change its position using the Coordinate
Display fields on the status bar. However, you
can change the sphere’s position using the
Reaction Manager’s editing tools.