Using the Spray and Snow Particle Systems

All I can say about the Spray and Snow particle systems is that when it rains, it pours. The Spray Parameters rollout, shown in Figure 35.2, includes values for the number of particles to be included in the system. These values can be different for the viewport and the renderer. By limiting the number of particles displayed in the viewport, you can make the viewport updates quicker. You can also specify the drop size, initial speed, and variation. The Variation value alters the spread of the particles' initial speed and direction. A Variation value of 0 makes the particles travel in a straight line away from the emitter.

Figure 35.2: The Spray Parameters rollout holds the parameters for the Spray particle system.

Spray particles can be Drops, Dots, or Ticks, which affect how the particles look only in the viewport. Drops appear as streaks, Dots are simple points, and Ticks are small plus signs. You can also set how the particles are rendered-as Tetrahedron objects or as Facing objects (square faces that always face the viewer).

Note 

The Facing option is visible only in the Perspective view.

The Timing values determine when the particles appear and how long the particles stay around. The Start Frame is the first frame where particles begin to appear, and the Life value determines the number of frames in which the particles are visible. When a particle's lifetime is up, it disappears. The Birth Rate value lets you set how many new particles appear in each frame; you can use this setting or select the Constant option.

The Constant option determines the Birth Rate value by dividing the total number of particles by the number of frames.

The emitter dimensions specify the width and height of the emitter gizmo. You can also hide the emitter with the Hide option.

Note 

The Hide option hides the emitter only in the viewports. Emitters are never rendered.

The parameters for the Snow particle system are similar to the Spray particle system, except for a few unique settings. Snow can be set with a Tumble and Tumble Rate. The Tumble value can range from 0 to 1, with 1 causing a maximum amount of rotation. The Tumble Rate determines the speed of the rotation.

The Render options are also different for the Snow particle system. The three options are Six Point, Triangle, and Facing. The Six Point option renders the particle as a six-pointed star. Triangles and Facing objects are single faces.

Tutorial: Creating rain showers

One of the simplest uses for particle systems is to simulate rain or snow. In this tutorial, you use the Spray system to create rain and then learn how to use the Snow system to create snow.

To create a scene with rain using the Spray particle system, follow these steps:

1. Open the  Simple rain.max file from the Chap 35 directory on the DVD. This file includes an umbrella model created by Zygote Media.

2. Select the Create Particles Spray menu command, and drag the icon in the Top viewport to cover the entire scene. Position the icon above the objects, and make sure that the vector is pointing down toward the scene objects.

3. Open the Modify panel, and in the Parameters rollout, set the Render Count to 1000 and the Drop Size to 2. Keep the default speed of 10, and select the Drops option; these settings make the particles appear as streaks. Select the Tetrahedron Render method, and set the Start and Life values to 0 and 100, respectively.

   Note 

   To cover the entire scene with an average downpour, set the number of particles to 1000 for a 100-frame animation.

4. Open the Material Editor (by pressing the M key), and drag a light-blue-colored material to the particle system icon.

Figure 35.3 shows the results of this tutorial.

Figure 35.3: Rain created with the Spray particle system

Tutorial: Creating a snowstorm

Creating a snowstorm is very similar to what you did in the preceding tutorial. To create a snowstorm, use the Snow particle system with the same number of particles and apply a white material to the particle system.

To create a scene with snow using the Snow particle system, follow these steps:

1. Open the  Snowman in snowstorm.max file from the Chap 35 directory on the DVD. This file includes a snowman created using primitive objects.

2. Select the Create Particles Snow menu command, and drag the icon in the Top viewport to cover the entire scene. Position the icon above the objects, and make sure that the vector is pointing down toward the scene objects.

3. Open the Modify panel, and in the Parameters rollout, set the Render Count to 1000 and the Flake Size to 6, and use the Six Point Render option. Set the Start and Life values to 0 and 100, respectively.

4. Open the Material Editor (by pressing the M key), and drag a white-colored material with some self-illumination added to the particle system gizmo.

Figure 35.4 shows the results of this tutorial.

Figure 35.4: A simple snowstorm created with the Snow particle system