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824 Chapter 13: reactor
• Reduce the complexity of the geometry used
for the rigid bodies. Try using bounding boxes
or sphere, and avoid using non-fixed concave
objects. Use simpler geometry as a geometry
proxy (page 2–719) for the object.
• If you are using Fracture, slowdowns can be
caused by reactor trying to avoid instability.
Follow some of these tips (page 2–773) to help
reduce the chances of instability happening
•Trydecreasingthenumberofsubsteps (page
2–806) used in the simulation. Be aware that
this will reduce the accuracy of the solution and
thereforemaycauseinstability.
Wa ter do e sn’t render.
The reactor Water (page 2–801) is a world-space
modifier and therefore it is not a renderable object.
You can bind renderable object (like planes) to the
water WSM in order to render a water animation.
See Rendering Water (page 2–803).
Cloth/Sof t/Rope becomes unsta ble a nd
ex pl odes .
•Checkwhetheranyunyieldingrigidbody
or DefMesh (page 2–793) is forcing the
Cloth/Soft/Rope into a penetration.
•Ifyouareattaching to a rigid body (page 2–798),
make sure that the p oints of attachment a re
outside the r i gid body; otherwise, make sure
Ignore Collision is on.
• If your Cloth/Soft/Rope is attached to a rigid
body (page 2–798),useRunge-Kuttaasthe
ODE Solver for the Rigid Body Collection (page
2–723) of the attached ri gid body
• Try increasing the amount of internal steps
in the Cloth/Soft/Rope collection (Advanced
rollout).
R igi d bodi es become unst abl e/ex plode/
fly to infinit y.
In rare situations, simulation can become unstable
and objects can "explode.” This typically happens
only when using complex systems of objects, like
Fracture (page 2–770),orusingsimple constraints
(page 2–727) like springs or dashpots.
•Forbestresultswhenusingrigidbodiesonly,
set Utilities panel > reac tor > About rollout >
Choose Solver to Havok 3.
•Ifyouareusingmanysimple constraints (page
2–727) (spring, dashpots) working together,
switching the ODE Solver in the Rigid Body
Collection (page 2–723) to Runge-Kutta can
improve the results.
•Usually,increasingthenumberofsubsteps
(page 2–806) in the simulation improves t he
stability of the simulation.
• Also for springs and dashpots, avoid attaching
objects with ver y d ifferent masses. Using a
Strength value similar to the mass of the objects
attached,andaDampingvalueof1/10thofthat
Strength usually give good results.
•Ifyouareusingconstraints (page 2–724),make
sure you ha v e aligned the constrain t spaces
(page 2–725) properly.
• If many objects star t the simulation too close
too each other (inside collision tolerance),
reactor will try to push them apart at the
beginning of the simulation. Try increasing t he
space between them, or reducing the collision
tolerance.
• If you have constrained two rigid bodies so they
are in continuous con tact/penetration (like an
upper arm and a forearm), be sure to disable
collisions (page 2–810) between those bodies.
•Addingdrag action canhelpdamptheoverall
simulation. Try increasing the linear drag in
the scene.