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800 Chapter 13: reactor
Soft Selection
You can use deformable constraints to specify
that you want certain vertices of a deformable
object to follow a user-specified animation, such
as skinning, while the rest of the object is f ully
physically simulated. However, sometimes this
canresultinavisible"join"betweentheanimated
and simulated parts of a piece of cloth, soft b ody
or rope.
To deal with this, the Cloth (page 2–778), Soft Body
(page 2–784),andRope (page 2–789) modifiers
have a Use S of t Selection option. The option can
help smooth t ransitions between the keyframed
and simulated vertices.
The following illustration shows the effect of
usingthisoption.Theclothtubeonthelefthas
a keyframed top and a simulated b ottom, with
a visible join. The cloth on the right uses soft
selection to blur the line between the two.
Pr ocedur es
To use soft selection when animating a deformable
body:
1.
Before you apply the reactor modifier to a
deformable body, apply a modifier that has a
Soft Selection option to your object, such as
Edit Mesh (page 1–634) or Mesh Select (page
1–719).
You can also apply this modifier to the body
later, but it’s important that it be below the
reactormodifierintheobject’smodifierstack.
2. Follow the instructions in Keyframing Vertices
(page 2–797) to keyframe selected points for
the deformable body, then create your reactor
animation.
3. With the body selected, open the selection
modifier in the modifier stack, and access the
Vertex sub-object le vel.
4. Select the vert ices that should appear f ully
physically simulated. For instance, for a piece
of cloth where the top section is keyframed, you
mightwantonlythebottomverticestoappear
to be fully affected by the physical simulation.
5. On the Soft Selection rollout, turn on Use Soft
Selection.
6. Set the Falloff value to specify a smooth falloff
from the selected vertices to the unselected
ones.
This is represented visually in the viewport.
7. NowopenthereactormodifierandturnonUse
Soft Selection.