2009

Seed Specifies a randomization value.
New Calculates a new seed using a randomization formula.
Speed By Surface Operator
Particle View on page 2811 > Click Speed By Surface in an event or add a Speed
By Surface operator to the particle system and then select it.
The Speed By Surface operator lets you control particle speed and direction
with any object or objects in the scene. This is in contrast to the default
Speed
operator
on page 2871, which uses the Particle Flow icon to control particle
speed and direction. Speed By Surface also provides options for controlling
speed by materials in the scene, and continuous speed control.
Typically, you use Speed By Surface to assign speed and direction characteristics
based on the objects used as emitters with the
Position Object operator on
page 2853. That is, you assign the same objects as emitters with Position Object
and as Surface Geometry objects with Speed By Surface.
TIP For greater control over particle motion on the surface, apply a Speed operator
on page 2871 before the Speed By Surface operator in the same event. Use the Speed
operator to specify particle direction on the surface, and the Speed By Surface
operator to adjust the vertical component of the speed vector to follow the contour
of the surface.
See also:
■
Speed By Icon Operator on page 2876
■ Keep Apart Operator on page 2894
Procedures
Example: To use Speed By Surface:
The Speed By Surface operator offers a wealth of possibilities for usage. This
procedure will lead you through several examples, but you're encouraged to
explore the operator further on your own to learn more about it.
1 Start or reset the software, and add a Particle Flow system. Position the
source icon at the world origin (X/Y/Z=0), and set the icon's Length and
Width values both to 30.
2886 | Chapter 14 Space Warps and Particle Systems