9

Soft Bodies 783
Advanced rollout
Internal Steps—Because deformable objects are
more complex to simulate, it is usually necessary
to perform more simulation steps (page 2–709)
to increase stability. This parameter specifies
the number of steps reactor performs internally
to simulate objects in this collection for each
simulation substep taken globally during the
simulation. For example, at 60 fps, simulating
at one keyframe (step) per frame, 10 substeps,
at three internal substeps for this collection,
reactor simulates the objects in this collection
using 60x10x3=1,800 steps per second, w hi le the
simulation in general uses 60x10=600 steps every
second.Thisallowstheobjectsinthiscollection
to be simulated more accurately without slowing
down the rest of the simulation. In general terms,
you can think of it in this way:
• Precision (stability) of overall
simulation=Number of Substeps (as
specified on the Preview and Animation rollout
(page 2–806))
• Precision (st ability) of objects in
this collection=(Precision of overall
simulation)x(Interna l Substeps)
Reset Default Values—Restores Internal Steps to its
default va lue.
Soft Bodies
Soft bodies are three-dimensional deformable
bodies (page 2–777).LikeCloth (page 2–778)
objects, they modify meshes. The main difference
between cloth as soft bodies is that soft bodies
haveanotionofshape:asoftbodytries,tosome
extent, to keep its original shape.
Youcanusesoftbodiestosimulatesquashyobjects
like a partially deflated beach ball, a water bottle,
jelly, or fruit. Th ey are also us eful for adding
realistic secondary motion to your objects and
characters: floppy ears, noses, tai ls, etc.
reactor provides two methods for simulating soft
bodies:
• The mesh-based method uses the vertices in
the mesh to operate (as with cloth and rope).
• FFD soft bodies (page 2–786) manipulate the
control points in an FFD grid instead.
Dependingonthecomplexityofyourobjectsand
the des ired effect, you can use either method. The
followingsectionsgointomoredetailaboutthem.
• Soft Body Modifier (page 2–784):Applyitto
each mesh to be deformed as soft body.
• FFD-based soft bodies (page 2–786):Softbodies
deformed by an FFD modifier