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358 Chapter 12: Animation
Reaction Controllers
Track View > Highlight a track in the Trac k Vie w hierarc hy.
> Assign a Reaction-type controller (e.g., Position
Reaction).
Select an object. > Motion panel > Assign Controller
rollout > Highlight a tra ck. > Click Assign Controller
> Choose a Reaction-type controller (e.g., Position
Reaction).
The Reaction controller is a procedur al controller
that lets a parameter react to changes in any other
parameter in 3ds Max. Typically, most of the setup
involving Reaction controllers is done with the
Reaction Manager dialog (page 2–361).Youuse
the dialog to define a master,whichisanobject
that controls other objects, and, for each master,
any number of slaves, which are objects the master
controls.Alternatively,youcanassignaReaction
controller directly to a slave object using Track
V iew or the Motion panel (as you would any other
controller), and then use Reaction Manager to
specify its master and other parameters.
Reaction controllers come in five different types:
Position Reaction, Rotation Reaction, Point3
Reaction, Scale Reaction, and Float Reaction. You
canassignaReactioncontrollertoanyanimatable
track in the scene. Reaction is not based on time,
butratheronothervariablesinyourscenesuch
as position or rotation.
You can use a Reaction controller to turn on a
lightasanobjectnearsagivenpoint.Musclescan
bulge as an arm bone rotates. A ball can s quash
automatically as the ball’s Z position nears the
ground plane. Feet can rotate as their heels are
lifted from t he floor.
A particle system can b e tri g gered by any g iven
event. Morph target percentages can be controlled
by events.
Note: The Reaction controllers replace the Reactor
con trollers found in previous versions of 3ds Max.
If you load a file containing a Reactor controller
into this version of 3ds Max, the Reactor controller
is converted to a Reaction controller, with all
settings and reactions fully intact.
See also
Using Manipulat ors with Reaction Contr ollers (page
2–369)
Procedures
Exa mple: To mak e the position of a sphere react to
the position of a box:
This procedure shows an alternate way to use a
Reaction controller. The recommended workflow
is to do most of the setup in the Reaction Manager
dialog: See Example: To use the Reaction Manager
dialog: (page 2–361).
Note: Objects don’t need to be animated to use
Reaction controllers. This procedure starts w ith
animation to make the reaction easier to see.
1. On the left side of the Top viewport, create a
box about 30 units on a side.
2. Animate the box from position (-100,0,0) at
frame 0 to position (100,0,0) frame 100.
3. IntheFrontviewport,createasphere
slightlyabovethebox.Positionthesphereat
(-100,0,50 ).
4. Go to the Motion panel, and on the
Assign Controller rollout, click the Position
track to highlight it.