2009

Adjust this ratio to that of the particle-map imagery. For the commonly used
TV aspect ratio of 4:3, set W/H Ratio=1.33. The parameter is not animatable.
Range=0.001 to 1000. Default=1 (square particles).
This value is not animatable.
Orientation
Use this drop-down list to choose how particles rotate on the axes not specified
by the Look At direction. Default=Align to Horizon.
Align to Horizon Keeps the top edge aligned with the horizon (the world XY
plane).
Align to Speed Follow Uses the right side of each particle as the leading edge,
so the top and bottom edges are aligned with the direction of particle motion.
Random Orients the top edge at random.
Allow Spinning To spin the particles, choose this option, and in the same
event use a
Spin operator on page 2863. In the latter, set Rotation Axis to Particle
Space and use the default axis values: X=0, Y=0 , Z=1.
Uniqueness group
The Uniqueness setting enables changing the randomization of the size/width
variation.
Seed Specifies a randomization value.
New Calculates a new seed using a randomization formula.
Shape Instance Operator
Particle View on page 2811 > Click Shape Instance in an event or add a Shape
Instance operator to the particle system and then select it.
Shape Instance lets you use any reference object on page 8107 in the scene as
particles. You can effectively define only one reference object per event, but
the object can comprise any number of sub-objects, each of which Particle
Flow can treat as a separate particle. Also, using tests, you can divide the
particle stream into multiple branches and define a different particle shape
for each.
As the name of the operator indicates, reference geometry is instanced into
the particle system. Thus, any physical changes you make to the original
2904 | Chapter 14 Space Warps and Particle Systems