9

822 Chapter 13: reactor
shape (deform), use deforming meshes (page
2–793) (
Note: Unyielding rigid bodies are much faster and
simpler to simulate than deform ing meshes.
Can r eactor stor e collisi ons f or
defor mable bodies (S oft, Cloth, R ope)?
No. The stor ing collisions (page 2–774)
functionality applies only to rigid bodies.
What are the limitations of Wa ter (page
2–801) in reactor?
Water in reactor is simulated as a height field
(points are displaced vertically only). This can
produce effects like ripples and waves, but it
cannot reproduce certain other effects:
•Wakes
• Splashes. You can, though, use the information
exposed through MAXScript to generate
particles or other effects.
• Flowing fluids (like water flowing through a
pipe or pouring from a tap).
CanImovethecenterofmassofmy
obj ects? How?
You can’t explicitly set the center of mass of an
object. However , you can use compound rigid
bodies where different pieces have different
masses to simulate uneven mass distribution. For
example, you c an simulate an object with a low
center of gravity by dividing the object into two
pieces (primit ives), top and bottom, w here t he
bottom piece is heavy and the top piece is light;
alternatively, you leave the original piece intact,
w ith low mass, and add a small, heavy primitive at
the point of the desired center of mass. For more
information, see Compound Rigid Bodies (page
2–722).
Can I at tach Cloth/R ope/S of t B odies to
other Cloth /R o pe/S oft B odi es?
No. However, once a piece of, say, cloth has
been simulated, you can take it out of its Cloth
Collection and add it to a Deforming Mesh
Collection (page 2–794).Bydoingso,thecloth
w ill stil l be part of the simulation the next t ime,
but reactor won’t recalculate its animation. You
can then attach other pieces of Cloth/Soft/Rope
to it by using the Attach T o Deforming Mesh (page
2–799) constrain t.
How can I make a rigid body not move
until a collision happens?
Yo u c a n u s e t h e Inactive property for the rigid
body.
How can I ani mate a fl oati ng obj ect, l ike
a bal loon?
There are many alternatives you can try:
•Usewater (page 2–801).Thebuoyancyofa
balloon in the air follows the same r ules as the
buoyancy of a light object inside a fluid. You
will need to place the water surface well abov e
the scene so the objects are not visible when
they reach it.
• Use very low mass for the objects , and add
wind (page 2–803) blowing in the up direction.