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Introducing Dynamics Simulation 707
The reactor Quad Menu
A further quick way to access reactor options is
the reactor quad menu. To open this menu, press
Shift +Alt and right-click in the act ive viewport.
Helper Icons
Many reactor elements, such as constraints and
theRigidBodyCollection,havetheirownspecial
helper icon that appears in the viewport when you
add them to the scene. For instance, the following
illustration shows the Hinge constraint icon:
Although the helper icon doesn’t appear in your
rendered scene, the icon’s appearance (and in
some cases, its position and orientation) will help
you to set up your reactor scene correctly.
When selected, reactor icons are white and are also
larger than when not selected. When not selected,
the icon for a valid element is blue, and for an
invalid element is red. What constitutes validit y
depends on the particular reactor element. For
instance, a hinge (page 2–747) is valid if it has the
correct number of objects attached to it; a Rigid
Body Collection (page 2–723) is va lid if it’s not
empty. Invalid elements are excluded from the
simulation, and reported as errors.
Certain icons provide additional information
about how the element behav es in the sim ulation.
For example, the display for a valid hinge indicates
the hinge position, and, when selected, the h inge
axis and any limits you have specified for the
move ment of the hinged bod ies.
Introducing Dynamics Simulation
This section gives a broad overview of physical
simulation, and introduces some concepts you
might find useful when working with reactor.
Physical Simulation
Havok’s physics technology, used in reactor, relies
onaprocessknownasphysical simulation in order
to provide a dynamic environment for the objects
in a scene. So what exactly does physical simulation
mean?
It is a process that automatically determines the
motion of objects according to their physical
properties. It achieves this by encapsulating some
physical laws, like Newton’s laws of motion, within
a robust, efficient engine, which calculates the
position of each object as t ime passes. In much
the same way that a motion picture is composed
of many individual images or frames, physical
simulation splits time into small discrete steps and
predicts the motion of each object during each
step. The cumulative effect of all these steps is
fluid, continuous, believable motion.