Particle Systems
(1) What«s a particle system?

Almost always in computer graphics the focus is on constructing a surface model, applying color and texture to it, then lighting it and seeing what it looks like from different angles. This way of going about things works well for physical objects that we can hold or touch, like cars, airplanes, or even people, but it doesn«t work at all for things like fire, rain, smoke, tornadoes, etc.

A great many visual effects in the real world are composed of the behaviors of many thousands of individual objects, all acting on their own in a physical system.

Rain is a good example of this, because when we see rain we are actually looking at light scattered by thousands and thousands of tiny droplets, each with a different size and shape, falling through the air directed by gravity, wind, and other complex forces in the real world.

Modeling each rain drop and then animating it along its path to the ground would be tremendously time consuming, and would never look like the real thing.

But what if you could just instruct your computer to create a large number (thousands) of tiny rain drops every second, and apply physical forces to each of them at every frame? Computers are pretty good at that kind of repetitive task carried out on a large number of objects.

So, that«s exactly what a particle system program does. It creates a large number of small objects, and allows you to control the size, shape, color, variance, mass, and many other parameters for each one, and then shows you what would happen as you apply different physical forces.

There are two distinct types of particle generation programs: geometry based and non-geometry based systems. Geometry based systems create a tiny polygonal object for each particle, as simple as a 8 polygons stitched together, and then render these tiny polygonal objects with the same renderer used for regular surface objects. The advantage of this method is that the particles can exist in the regular scene, and be rendered at the same time as the regular scene, adding reflections and shadows to the finished work. The disadvantage of this method is that hundreds of thousands of particles create millions of polygons to be rendered for each frame, slowing down the render considerably.

Non-geometry based systems use only an imaginary point in space for each particle, without any solid geometry, and then render the location of each particle by applying a dab of color to your screen at the position of that infinitely small point. The advantage of this sort of system is extreme speed and flexibility, while the disadvantage is that the particles must be rendered separately and then combined with the original scene.

The portion of the Softimage 3D|Extreme package dedicated to particles is called, you guessed it, Particle, and it is by default a non-geometry based system. However, the particles can be imported back into the regular Softimage 3D program and replaced with geometric objects if you wish.

(2) What«s it good for?

Particle is an excellent way to create special effects, from fogs, to fires, to death rays, to explosions. It«s also a great deal of fun to play around with.

The interface is very simple, and consists of one large window area, that can be switched to be any orthographic view, a perspective view, or a camera view that matches motion in a Softimage scene. Being able to match the camera motion of a scene is called Motion Control in the real world, and it«s critically important because it can keep the camera view of the rendered particle effects conformed to the same camera view of the rendered scene at each frame. If you didn«t do this, you couldn«t move the camera in shots that had a particle effect.

Modules across the top give you access to different areas of functionality.

The Particle module is where you define what each individual particle will look like. There may be as many different kinds of particles as you wish to make.