Java Reference
In-Depth Information
return result;
public function randomFromNegToPos(max:Number):Number{
if (max == 0.0){
return 0.0;
var result = max - random.nextFloat()*max*2;
return result;
Listing 2-10 shows there are two new attributes to the class Emitter : particleHue and
particleHueVariation . The attribute particleHue can be used to adjust the color of the Particles and
the attribute particleHueVariation determines how much to randomly adjust the color of each
Particle .
The emit function of class Emitter is slightly changed. Now, the attributes scaleX and scaleY are set
to control the size of the particle. The attribute effect is set on the Particle to a ColorAdjust effect. This
effect alters the color of the node it is attached to; in this case, we adjusting the hue of the Particle . This
is what changed the color of the Particles in Example 5 from red to blue.
The function normalizeHue simply makes sure that the value passed to hue is of the correct range,
-1.0 - 1.0. When dealing with random numbers it is easy to accidentally set a bad value.
The function randomFromNegToPos is a utility function for generating random numbers from a
negative max to a positive max.
Example 6: Direction
When trying to reproduce some effects, it becomes clear that having the particles free to travel in any
direction is undesirable. For example, when simulating a candle's fire, the particles should move
upward. However, a candle's fire also flickers a little; adding a slight variation to each particle's direction
will help simulate that effect. The following example explores how to set the general direction of each
particle, as well as dictate the range of variation. The screenshot in Figure 2-9 shows a fire effect.
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