Changing the Emitter Shape

So how do you spread out your particles? All you need to do is change the emitter shape. The Emitter Shape parameter includes a pop-up menu with six choices:

• Point Emits particles that emerge from a single point in the center of the emitter. This is the default setting and is why all the fish are stacked in the same spot in the frame.

• Line Emits particles that emerge in a line. You can specify the coordinates of where the line begins and ends.

• Circle Emits particles that emerge from the edge of a radius around the center of the emitter. You can adjust the diameter of the circle to make it larger or smaller.

• Filled Circle Emits particles that emerge from a circle around the center of the emitter. You can adjust the radius of the filled circle to make it larger or smaller.

• Geometry Emits particles that emerge in whatever shape you add to the Shape Source well.

• Image Emits particles that emerge from an area defined by an image you add to the Image Source well.

Let's experiment with some of the Emitter Shape options and find the one that works best for our school of fish.

1.	On the Emitter tab, click the Emitter Shape pop-up menu and select Line. The fish appear dispersed in a line on the Canvas. This may work for a fish parade, but it still doesn't look very natural. Let's try another setting.
2.	From the Emitter Shape pop-up menu, choose Circle. It's better, but why would the fish leave a hole in the middle of their formation? Are they mourning a fallen comrade? I don't think so. Next!
3.	From the Emitter Shape pop-up menu, choose Filled Circle. We have a winner. The emitter shape is fine, but it could be even better if the fish were clustered a little differently.

Changing the Random Seed

The Motion Particle generator creates particles using random sequences of values based on the other parameters applied to the particle. Each set of random values selected by the generator has a number called the random seed. If you don't like the random pattern or behavior that has been applied to the particles, you can click the Generate button to create a different random seed number. The new number will change the behavior pattern to a different variation. The Generate button is located near the bottom of the Emitter tab.

The Random Seed value is located in the field to the right of the Generate button. When you click the Generate button, the Random Seed number changes in the field, and the random behavior of the particles changes to reflect a new random sequence of values. Changing the random seed does not change absolute values that you have applied to the particles. However, it does change the range values and any parameters that rely on randomly generated numbers.

Let's change the random seed for the particles until you like the way the school of fish looks.

1.	On the Emitter tab, for the Random Seed parameter, click the Generate button to change the random seed. The Random Seed number changes, and so does the pattern of fish on the Canvas.
2.	Click the Generate button until you get a pattern that you like. You can use any random seed that you wish, or you can use the same number that I am using (1193307618).
3.	Press Cmd-S to save your progress.

Adding a Scale Range to the Particles

You've created the school of fish particles. Now let's change the Scale and Scale Range parameters to give the fish a range of sizes.

1.	On the Emitter tab, in the Scale value field, type 50 and press Return to change the scale of all the fish to 50 percent of the original object size.
2.	In the Scale Range value field, type 30 and press Return to change the scale of the fish to a range of 30 percent larger to 30 percent smaller than the original object. Now the fish come in a variety of sizes. Let's extend their lives to last the entire duration of the project.
3.	On the Emitter tab, change the Life value to 10.00 (10 seconds).
4.	Press Cmd-S to save your progress.