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722 Chapter 13: reactor
Display
Use Dis play Pr oxy —When on and you specify
a proxy object by clicking the Proxy button,
reactor displays the specified proxy In the Preview
Window in place of the object.
Compound R i gid B od ies
Rigid bodies can be made of one or more objects,
or primitives. For instance, if you assign physical
properties to an object in a scene and add it to
aRigidBodyCollection,wesaythattherigid
body has one primitive. However, reactor can also
sim ulate a rigid body made up of more than one
primitive. To do this, you need to g roup objects
together using the 3ds Max Group menu. You
canthenaddthegrouptothecollection,andthe
objects in the group then become the primitives
that ma ke up the rigid body.
Creating such compound rigid bodies can be
useful, as it is much faster to simulate a rig id
body made up of convex pieces than to simulate
amorecomplexconcaveshape.Inaddition,the
primitives that make up a compound r ig id b ody
can have different masses, s o you can create ri gid
bodies that have nonuniform mass distribution.
For example, you can create a hand axe where the
head is heavier than the handle, so that if you toss
the axe it spins around its head.
Yo u c a n d o t h i s b e c a u s e t h e M a s s p r o p e r t y o n
the Rigid Body Properties dialog is assi gned to a
specific primitive rather than an entire rigid body,
unlike most of the other properties in this dialog.
For single-primitive rigid bodies, this distinction is
unimport ant. However, in the case of a compound
rigid body, the group parent is the rigid body and
cannot have a Mass value assigned: Mass can be
assigned only to its children, the primitives.
Simulation geometry is also defined at a primitive
level, so you can combine concave and convex hull
geometries in a single rigid body.
Procedures
To create a compound rigid body:
1.
Arrange the objects to use to make up your
compound rigid body.
2. Select all of the objects.
3. From the Group menu, choose Group.
Your objects are now a ll child objects of a new
group parent. You can add this parent object to
aRigidBodyCollection.
To edit compound r igid body properti es:
1.
With the compound rigid body selected,
choose Group > Open.
2. To edit the compound rigid bo dy’s properties,
selecttheparent(dummy)andgotothe
properties rollout of the utility or open the
Rigid B o dy Properties dialog. You cannot
edit the Mass or Simulation Geometry values
for a group p arent because they are primitive
properties.
Tip: It’s easier to select a group parent using the
Select Objects dialog (page 1–78) with Display
Subtree enabled: The group parent is displa yed
above its members.
3. To edit one of the rigid body’s primitive’s
properties, select the appropriate child and
gotothePropertiesrolloutoftheutilityor