9

Troubleshooting 825
• If you are working with Fracture, the Fracture
Tips (page 2–773) section provides information
on how to avoid instability.
Cloth/S of t /R ope object str etches too
much
If you have attached (using the Attach to RB
Constraint (page 2–798))ittoafallingobject,
be sure to turn off Do Not Affect Rigid Body. If
the problem remains, increase the mass of the
Cloth/Soft/Rope, or decrease the mass of the
attached r ig id body. Increasing the strength and
damping of the Cloth/Soft/Rope should also
improve the situation.
Objects s eem to move v er y sl owly
Make sure you are using the proper World Scale
(page 2–808) in the scene. A 10cm box falling from
a1mheightdoesn’tbehavethesameasa1kmbox
falling from a height of 10km: The second one will
reach the ground much later). Use real-world units
orhaveapropermappingbetween3dsMaxunits
and simulation units (World Scale (page 2–808)).
Why, af ter si mulation, do I get warnings
regarding "topology changes"?
The term “topology” refers to the internal
connections of the vertices, edges and faces of a
mesh. Ifyouchangethenumberofverticesin
amesh,youarechangingitstopology. While
3ds Max lets you animate the topology of objects
(e.g., change the number of vertices or f aces over
time), reactor c an simulate only objects with
fixed numbers of vertices. If, during a simulation,
reactor detects a topology change, it ignore s the
object in question and reports the problem as a
warning .
Objects inter penetr a te.
There can be different reasons for this:
• Check that you haven’t disabled collisions for
those bo d ies. You can disable collisions either
globally (page 2–810) for pairs of objects, or for
the object in particular (Rigid Body Properties
(page 2–717)).
•Iftheobjectsareattachedusingdeformable
constraints (page 2–795),makesureyouhaven’t
disabled collisions in the constraint parameters.
•MakesureCollision Tolerance is set to a value
that makes sense for the sizes of the objects.
•Tryincreasingthenumberofsubsteps (page
2–806) in the simulation.
Cloth/S of t/R ope i nter sects i ts elf.
Make sure you have turned on the Avoid
Self-Intersections option in the modifier (page
2–777).
I can’t add an object to a Cloth/Soft/R ope
Collection.
Only an object that has the proper reactor modifier
applied can be added to one of these collections.
Make sure you have applied a reactor Cloth (page
2–778), Soft B ody (page 2–784),orRope (page
2–789) modifier to the object.
I can’t add an object to a R igid B ody
Collection.
If you are using compound bodies (page 2–722),
make sure the group is open, as only the group
parent can be added to a Rigid Body Collection
(page 2–723).
Ma ss a nd other properties a re dis abl ed.
Make sure you h ave selected only one object, and
that this object is geometrical. The most common
cause for this is the use of groups. You can use
groups to create compound rigid bodies (page
2–722), but in order to change the properties of