INSIDE 3DS MAX® 7 [Electronic resources] نسخه متنی

Chapter 16. Physics and Dynamics

By Michael Hurwicz

You have at your fingertips an awesome weapon. It's the secret weapon used in The Matrix Reloaded when Neo (Keanu Reeves) sends bad guys in black suits and sunglasses flying through the air like rag dolls. (And you thought it was that stick he was swinging!) It's the same technology used for collisions, explosions, and assorted madness and mayhem in dozens of games, from Auto Assault to Psi-Ops: The Mindgate Conspiracy. It's the Havok physics simulation engine, known in its 3ds max incarnation as reactor.

The basic magic of reactor is that it creates physically accurate keyframes for you. Frank Wilczek, winner of the 2004 Nobel Prize in Physics, has been quoted as saying, "In physics, you don't have to go around making trouble for yourselfnature does it for you." In 3ds max 7, you don't necessarily have to make keyframes for yourself eitherthe reactor physics simulation plug-in will do it for you, faster than you could do it yourself, and (when properly applied) with far more realistic results. You create objects and provide values (or accept defaults) for properties such as mass, friction, and elasticity. The reactor plug-in calculates how objects with these properties would behave in the real world and creates keyframes to make them behave that way. reactor can also "read" keyframes that you create, to determine initial values for properties such as speed and direction of motion.

In reactor, soft bodies (objects that can squash, stretch, and bend to simulate rubber balls, insect antennas, fruit, and other flexible, deformable things) have properties like stiffness and damping. Cloth in reactor (typically used for objects like flags, curtains, and clothing) can have additional properties, such as stretch, bend, and shear. You can configure the air resistance of reactor rope (also commonly used to simulate hair). Water in reactor can have density, viscosity, and depth.

reactor also provides constraints that define how two objects move in relation to each other. For example, a Hinge Constraint can be used for a door hinge or an elbow joint. The Car-Wheel Constraint implements the motion of a wheel on an axle. The Rag Doll Constraint is designed to duplicate the motion of the human shoulder and other joints.

The Create Object option on the reactor menu on the Main toolbar shows all the different types of collections, objects, and constraints that can be created with reactor (Figure 16.1). All the same options are available on the reactor toolbar (Figure 16.2) on the left-hand side of the screen. (Figure 16.2 shows the reactor toolbar oriented horizontally in order to display all the options. You may also prefer to undock the reactor toolbar and position it horizontally, to avoid having to scroll the toolbar to get to the buttons you want.)