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212 Chapter 11: Space Warps and Particle Systems
Uniqueness group
The Uniqueness setting enables randomization of
the test value var iation.
Seed—Specifies a randomization value.
New—Calculates a new seed using a randomization
formula.
Collision Test
Particle View (page 2–125) > Click Collision in an e vent or
add Collision to the par ticle system and then select it.
Collision tests for particles that collide with one or
more specified Deflector space warps. It can also
test whether a part icle has slowed down or sped
up after one or more collisions, has collided more
than once, and even w hether it will collide with a
deflector in a specified number of frames.
The Collision test supports all deflector space
warps except the DynaFlect deflectors:
• POmniFlect (page 2–78)
• SOmniFlect (page 2–84)
• UOmniFlect (page 2–85)
• SDeflector (page 2–87)
• UDeflector (page 2–89)
• Deflector (page 2–90)
Tip: When testing for collisions with multiple
deflectors, for best results, place a ll the deflectors
in a single Collision test. This tests for collisions
with all the deflectors simultaneously, and helps
avoid possible missed collisions.
See also
Collision Spawn Test (page 2–215)
Procedure
Ex ample: To test for pa r ti cles slowing down af ter one
or more collisions:
In the real world, par ticles bouncing repeatedly
against a surface lose kinetic energy at each
collision, and slow down gradually. Rather than
testing for a specific number of bounces, you can
use the Is Slow After Collision(s) to test whether
particle speed has sunk below a specific level.
1. Start or reset 3ds Max. Set the animation length
to 500 frames.
2. Add a Gravit y space warp and a Deflector space
warp. Decrease the deflector’s Bounce setting
below 1.0, and increas e the Variation and Chaos
valuesabove0.0.Setthedeflector’sWidthand
Length to 500.
3. Create a default Particle Flow system. Position
the emitter directly above the deflector.
4. Add a Force operator (page 2–204) to the end
of Event 01 and add the Gravity space warp to
the Force operator.
5. Create a new event with a Display operator
(page 2–202),andchangethedisplaytypetoa
different choice than is used in Event 01.
6. Add a Collision test to Event 01, below the
Forceoperator,andwireittothenewevent.
7. In the Collision test settings, add the deflector.
Choose Is Slow After C ollision(s), and set
Speed Min=100 (assuming you’re using the
default initial speed of 300).
8. Play the anima tion. You might need to adjust
one or more settings before seeing the expected
behav ior.
After several b ounces, the p articles change
in appearance and move steadily away from
the deflector, indicating that they’ve entered
the second event. Of course, you can set any
behavior you like in this event.