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724 Chapter 13: reactor
Rigid Bodies—
Lists the names of the objects in the
Rigid Body Collection.
Pick —Lets you add an object to the Rig id Body
Collection. Click this button, then in the viewport
movethecursorovertheobjectyouwouldliketo
add to the collection. If the object can be used as a
rigid body the cursor will change from an ar row
to a cross and you can select the object to add it to
the collection.
Add—Lets you add one or more objects from the
scene to the collection. Click the button to open
the Select Rig id Bodies dialog. Make a selection in
the provided list, and then click the Select button
to add the object s to the collection.
Delete—Lets you remove objects from the
collection. In the rigid bodies list, select the bodies
you would like to remov e from the collection and
click this button.
Disabled—When on, the collection and the bodies
it contains are n ot added to the simulation.
Advanced rollout
ODE S ol ver —Lets you choose the method by w hich
reactor simulates the collection:
•
Euler—The collection calculates the behavior
foritsrigidbodiesusinganEulerODE
(Ordinary Differential Equation) solver. Euler
is a fast method that provides goo d results in
most cases.
•
Runge-Kutta —This method is more accurate
in some cases but requires more computation.
UseRunge-Kuttaifyouhavemanyobject
connected using simple constraints (page 2–727)
like springs or dashpots, because those kind of
systems can easily become unstable.
Reset Default Values—Sets va lues for the collection
to their defaults. In this instance, it sets the ODE
Solver back to its default value.
Cons tra int s
With reactor, you can easily create a simple
physical simulation by simply assigning rig id bo dy
properties to objects and adding them to a Rigid
Body Collection. When you run the simulation,
objects c an fall from the sk y, slide across each
other, bounce off each other, and so on. However,
let’s say you wan t to simulate a real-world scene
suchasapersonpushingopenadoor. How,for
instance, do you make sure that the door rigid
bodydoesn’tjustfallontotheground,orthatit
swingsoutintheproperdirectionwhenpushed?
To accomplish this you use constraints.Theselet
you restr ic t t he possible movement of objects
in the physical simulation. Depending on the
type of constraint you use, you can hinge objects
together, attach them together with springs that
w ill snap back if the objects are pulled apart, or
even simulate the movement of a human body
joint. You can constrain objects to each other or
to points in space.
This section shows you how to work with
constraints in reactor. It includes the following
sections:
Constraint Concepts (page 2–725)
Simple Constraints (page 2–727), which incl udes
the following topics:
• Spring (page 2–727)
• Linear Dashpot (page 2–730)