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Rigid Body Properties 719
convex shape and other objects is always more than
the combined radii of the objects. Default=0.05.
Impor tant: Applies to Havok 3 only.
Addingashelltoanobjectcanimprove
performance. The core convex-convex
collision-detection algorithm is fast when objects
are not interpenetrating, and slower when they are.
Adding a shel l makes it less likely that the sh apes
themselves will interpenetrate, t hus reducing the
likelihood of using the slower algorithm. Using
a shell is thus faster in situations that involve the
risk of shapes interpenetrating; for instance, when
an object is sett ling or sliding on a surface, when
there is a stack of objects, or when many objects
are jostling together.
Penet. —(P enetration) The amount of penetration
reactor permits.
To avo i d t r y in g t o s o l ve i n s o luble phy s i c a l
problems, the Havok 3 engine allows penetration
between objects even if continuous physics is
enabled. Default=0.05.
Impor tant: Applies to Havok 3 only.
Quality—
Lets you set individual settings for each
object based on the desired level of interaction.
Default=Moving.
Impor tant: Applies to Havok 3 only.
The available Qualit y sett ings are:
•
Debris —Low-importance objects used for
adding visual quality.
•
Moving—Regular objects that populate the
world, such as furniture, etc.
•
Critical—Essential objects that are never allowed
to interpenetrate.
•
Bullet—Fast-moving projectiles.
Simulation Geometry
Lets you specify the physica l representation of your
object that will be used in the Havok simulation.
Proxies
reactor supports substituting one object for
another in two different ways: geometry proxies
and display proxies.
Geometry proxies allow you to specify a different
body’s geometr y as the simulation geometry for
an object. For example, you can have a complex
object displayed on-screen, but replaced for
simulation purp oses by a box, which is much easier
and faster for reactor to simulate. The box governs
the movement of the object, and dictates how it
collides, its position, and orientation. However,
on-screen you can see the complex object in full
detail. Geometr y proxies are applied per object.
Display proxies replace a rigid body’s display
body with that of another object. Therefore, they
affect display only during the real-time preview
(page 2–815) and do not affect animation. They
are applied per rigid body, rather than per object.
This means that you can create a compound rigid
body of several objects and simulate these, but
display an alternative mesh for the body during the
preview. You can find out how to specify a display
proxy in the Display (page 2–722) sect ion.
Convex and Concave Objects
A rigid body primitive is defined as convex if,
given any two points inside the object, you can
always go in a straight line from one to the other
w ithout leaving the object. Convex objects include
spheres, cylinders, and boxes. For example, a
sphere is convex but a golf ball is concave because
of the conca vities (dimples) in its surface. Also,
by definition, non-closed meshes (planes, hollow
hemispheres) are a lways concave.