Command entry:Particle View
Click Speed in an event or add a Speed operator to the particle system and then select it.
This is the default Speed operator, which appears in the first event when you create a new Particle Flow icon. It provides basic controls over particle speed and direction.
Directional controls provided by the Speed operator are based on the position and orientation of the Particle Flow icon. For best results when using other objects as emitters, use the Speed By Surface Operator operator instead.
Example: To change particles' speed:
The Speed operator works on an instantaneous basis: It sets each particle's speed once only, when it enters the event. Even if you animate the Speed value, each particle moves at a constant rate of speed, defined by the value at the time it enters the event. This procedure demonstrates a trick you can use to change particle speed with an animated Speed value, thanks to Particle Flow's looping ability.
The particles fall downward at the default rate: 300 units per second.
, and move the time slider to frame 30.
This animates the Speed value from 300 at frame 0 to 0 at frame 30.
.
Play the animation.
The particles born later move slower, but all still move at a constant rate of speed.
Play the animation.
All the particles slow down simultaneously and eventually come to a stop.
Here's how it works: As each particle enters Event 02, its speed is set to the current Speed value in the Speed operator. Particle Flow then sends the particle immediately to Event 03, where it sits for one frame. Event 03 then returns the particle to Event 02, whose Speed value is now lower. Particle Flow perceives the returned particle as newly entering the event, so it changes its speed to the current Speed value. Thus, the particles continually return to Event 02 one frame later than before, and are assigned a progressively lower speed.
If you wanted the particles to do something else after they stop, you could add a Speed Test to Event 02, above the Send Out test, set Test True If Particle Value to Is Less Than Test Value, and set Test Value to a very low value, such as 0.01. Then wire the Speed Test to a different event.
The user interface appears in the parameters panel, on the right side of the Particle View dialog.
The amount by which particle speed can vary, in system units per second. Default=0.0.
To obtain each particle's speed, the system multiplies the Variation value by a random number between -1.0 and 1.0, and then adds the result to the Speed value. For example, if Speed=300 and Variation=100, then each particle's speed would be between 200 and 400.
The Direction drop-down list lets you specify which way the particles go after they're born. Default=Along Icon Arrow. In
most cases, the actual direction also depends on the icon orientation. The primary exception is when Position Location is set to Pivot.
Particle movement is always in a straight line unless influenced by other factors.
Each particle moves along an imaginary line drawn between the particle's location and the icon center.
With the flat icon types (Rectangle and Circle), this results in all the particles moving in one plane, unless you increase Divergence above 0.0. With icons that have height (Box and Sphere), the particles move outward in three dimensions.
Particles at the center, as is the case when the Position operator's Location parameter is set to Pivot, arbitrarily move along the world X axis.
Each particle moves along an imaginary line drawn between the particle's location and the icon arrow. The line is perpendicular to the icon arrow, which is considered an infinite line for this purpose.
With the flat icon types (Rectangle and Circle), this results in all the particles moving in one plane, unless you increase Divergence above 0.0. With icons that have height (Box and Sphere), the particles move outward in a cylindrical formation.