9

56 Chapter 11: Space Warps and Particle Systems
When you bind multiple objects to a space warp,
the space warp’s parameters affect all the objects
equally. Ho wever, each object’s distance from the
space warp or spatial orientation to the warp can
change the warp’s effect. Because of t his spatia l
effect, simply moving an object through warped
space can change the warp’s effect.
You can also use mult iple space warps on one or
more objects. Multiple space warps appear in an
object’s stack in the order you apply them.
Note: You can take advantage of the AutoGrid
feature to orient and position new space warps
w ith respect to existing objects. See AutoGrid
(page 2–7) for details.
Space War ps and Supported Objects
Some types of space warp s are designed to work on
deformable objects, such as geometric primitives,
meshes, patches, and splines. Other types of war p s
work on particle systems such as Spray and Snow.
Five space warps (Gravity, PBomb, Wind, Mot or,
andPush)canworkonparticlesystemsandalso
serve special purposes in a dynamics simulation.
In t he latter case, you do not bind the warps to
objects, but rather assig n them as effects in t he
simulation.
On the Create panel, each space warp has a rollout
labeled Supports Objects Of Type. This rollout
lists t he ki nd of objects you can bind to the war p.
Basics of Using Space Warps
Follow these genera l steps to use space warps:
1. Create the space warp.
2. Bind objects to the space warp.
Click Bind To Space Warp on the main
toolbar (available from the Select And Link
flyout), and then dr ag b etween the space war p
and the object.
The space warp has no visible effect on your
scene u ntil you bind an object, system, or
selection set to it.
3. Adjust the space warp’s parameters.
4. Transform the space warp with Move, Rotate,
or Scale. The transforms often direct ly affect
the bound object.
You can animate space war p parameters and
transforms. You can also animate space warp
effects by animating transforms of an object bound
to the warp.
Particle Leak age and Deflector Space
Wa rps
Adeflectorisaspacewarpthatactsasabarrierto
particles in particle systems. Occasionally stray
particles can leak through a deflector under the
following circumstances:
• When a particle happens to hit the deflector too
near the end or beginning of a time interval,
and numerical error in the solution doesn’t
report a hit
•Whenaparticlehitstooneartheedgeofaface
referenced by a UDeflector, and neither face
finds it
• When a particle is moving quickly and first
appearstooclosetothedeflector,sothevery
firstupdatecyclewithintheparticlesystem
takes it past the deflector without the deflector
ever seeing it
Often this isn’t a problem be c ause the part icles
bounce off solid objects, so you don’t see the errant
particles. When it does cause problems, you can
use a planar deflector instead of a UDeflector, a
collection of planars to approximate the mesh, or a
simple mesh to replace the planar. The solutions
vary, so w here one has a glitch the other might
work just fine.