Introducing 3ds Max 9 3D for beginners apr 2007 - part 10 potx

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Particles and Dynamics

Animating large numbers of similar objects frequently can be a time￾consuming and arduous task. With hundreds, if not thousands, of individual objects and

their animated parameters and transforms to consider, this is a task that, one object at a

time, could quickly become overwhelming. 3ds Max has several tools for animating large

numbers of objects in a scene including instanced objects, externally referencing objects,

instanced modifiers, the Crowd utility for characters, and particle systems for controlling

any number of particles. Particles are usually small objects, often in large numbers, that

can represent rain, snow, a swarm of insects, a barrage of bullets, or anything else that

requires a large quantity of objects that follow a similar path.

Another method of creating animations for several objects simultaneously is through

the use of reactor, the physics engine contained within 3ds Max. Using reactor, you can

calculate the interactions between many rigid and soft body objects or simulate fluids or

rope dynamics.

Topics in this chapter include:

■ Understanding Particle Systems

■ Setting Up a Particle System

■ Particle Systems and Space Warps

■ Using Rigid Body Dynamics

■ Using Soft Body Dynamics

CHAPTER 12

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Understanding Particle Systems

Particle systems are a means to manage the infinite possibilities that can be encountered

when controlling thousands of seemingly random objects in a scene. The particles can fol￾low a tight stream or emanate in all directions from the surface of an object. The particles

themselves can be pixel-sized elements on the screen or instanced geometry from an object

in the scene. Particles can react to space warps, such as wind and gravity, and bounce off

objects called deflectors to give them a natural flow through a scene. Particles can even

spawn new particles upon collision.

All particle systems have two common components: the emitter and the particles. The

emitter, as you would guess, is the object from which the particles originate. The location

and, to a lesser extent, the orientation of the emitter are vital to the particles’ origination

point in the scene. Emitters are nonrendering objects, making their size and color unim￾portant. The particles themselves are the elements that spew from the emitter. The num￾ber of particles can range from a few (to simulate a burst from a gun) to thousands (to

simulate smoke from a burning building). The number of particles visible in a viewport

can adversely affect the viewport refresh speed and your ability to quickly navigate within

the viewports. By default, far fewer particles are shown in the viewports than actually ren￾der in the scene. This helps maintain a reasonable system performance level.

Particle System Types

Two types of particle systems are available in 3ds Max: event-driven and non-event-driven

particle systems.

Event-Driven Particle Systems

Event-driven particle systems use a series of tests and operators grouped into components

called events. An operator affects the appearance and action of the individual particles and

can, among many other abilities, change the shape or rotation of the particles, add a mate￾rial or external force, or even delete the particles on a per-particle basis. Tests check for

conditions such as a particle’s age, its speed, and whether it has collided with a deflector.

Particles move down the list of operators and tests in an event and, if the particles pass the

requirements of a test they encounter, they can leave the current event and move to the

next. If they do not pass the test, the particles continue down the list in the current event.

Particles that do not pass any test in an event commonly are deleted or recycled through

the event until they do pass a test. Events are wired together in a flowchart style to clearly

display the path, from event to event, that the particles follow.

Particle Flow is the event-driven particle system in 3ds Max, and it is a very compre￾hensive solution to most particle system requirements. The upper-left pane in the Particle

View window in Figure 12.1 shows a partial layout of the events in a Particle Flow setup.

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Events are the named boxes, operators are the gray boxes, and tests appear as yellow dia￾monds. To the right of the Particle View window is a common example of one of the

several emitter types that a Particle Flow can utilize. Using Particle Flow, you can create

almost any particle-based effect, including rain, snow, mist, a flurry of arrows and spears,

and objects assembling and disassembling in a blast of particles. Unfortunately, an in-depth

examination of Particle Flow is beyond the scope of this book.

Non-Event-Driven Particle Systems

Non-event-driven particle systems rely on the parameters set in the Modify panel to

control the appearance and content of the particles. All particles are treated identically by

the system’s parameters, and there are no tests to modify the behavior for certain particles.

Non-event-driven particle systems have been around for a long time; they are stable, easy

to learn, and an acceptable solution for many particle requirements. Non-event-driven

particle systems are the focus of this chapter. These particles can be bound to space warps

to control their apparent reactions to scene events, and they can be instructed to follow

a path.

Six different non-event-driven particle systems are available in 3ds Max; each has its

own strengths. They all have similar setups and, after you understand one type, the others

are easy to master.

Figure 12.1

The Particle View

window and a

Particle Flow emitter

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The Super Spray particle system is the most commonly used non-event-driven particle

system in Max. It features a spherical emitter with a directional arrow to indicate the ini￾tial direction of the particles. It has eight rollouts containing the parameters that control

the appearance and performance of the particles. The particles can emerge over a specified

range of time or throughout the length of the scene’s duration. When rendered, they can

appear as one of several 2D or 3D shapes, instanced scene geometry, or as interconnecting

blobs that ebb and flow as they near each other. The particles can even spawn additional

particles when they collide and load a predesigned series of parameters called a preset. The

Super Spray particle system essentially replaced the older, less-comprehensive Spray parti￾cle system, and it will be the main focus of this chapter.

Rather than being the emitter, the Particle Array particle system that is created in a

viewport is only a visual link to the particle system emitter itself. The PArray uses a scene

object as the emitter for the particles. While the parameters are adjusted with the PArray

selected, the particles are emitted from the vertices, edges, or faces of the designated object.

When used in conjunction with the PBomb space warp and the Object Fragments setting,

acceptable object explosions can be created.

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