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Simulating
Physics-Based
Motion with reactor CHAPTER

hen you speak of reactor in Max, you really are speaking of physics.
Physics is one of the coolest arms of science because it deals with the IN THIS CHAPTER
Wscience of matter and energy and includes laws that govern the
motions and interactions between objects. For animators, this is great news Exploring the reactor utility
because what you are trying to do is to animate the motions and interactions Learning to use collections
between objects.
Applying reactor modifiers
So, should all animators study physics? The answer is absolutely. Understanding
these laws through study and experience will sharpen your animating skills. But Assigning object properties
you can also take advantage of the work that other animators have done in under-
standing the laws of physics and turning them into a product that ships with Max. Working with reactor objects
The other animators are a group called Havok, and the product is reactor.
Previewing animations
The Havok physics engine included in Max is the same engine commonly used in
games to simulate game-world physics such as the reactions in Value’s Half Life 2.
Using reactor, you can simulate many physical properties and automatically cap-
ture keyframes as the objects interact. It’s like getting a physics degree for free.
The reactor menu includes everything you need to access the reactor physics
simulation engine. With reactor, you can define objects as rigid bodies like chairs
or bowling balls or as soft bodies like stuffed animals. You can also define spe-
cialized objects, including cloth and rope.
After physical properties are defined, you can define physical forces to act on
these objects and simulate the resulting animation. Not only does reactor make
difficult physical motions realistic, but it also is fun to play with.

Understanding Dynamics

Dynamics is a branch of physics that deals with forces and the motions they cause,
and regardless of your experience in school, physics is your friend—especially in
the world of 3D. Dynamics in Max can automate the creation of animation keys by
calculating the position, rotation, and collisions between objects based on physics
equations.

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