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time; the physics engine can make certain assumptions when detecting
collisions based on the fact that the objects' shapes don't vary from simulation
step to simulation step.
Both the Havok 1 and Havok 3 engines can simulate rigid bodies, but Havok
3 simulations are faster and more accurate.
Deformable Bodies
To simulate cloth, rope, or other material whose shape changes over time,
you need to use a different type of body: a deformable body. With deformable
objects, collision detection becomes much more difficult, given that the object
can change shape dramatically between time steps and can also attempt to
collide with itself. For this reason, deformable bodies are more expensive to
simulate.
NOTE Only the Havok 1 engine can simulate with deformable bodies.
Scale
Our scientific knowledge of physics is extensive. What we are concerned with
here would more accurately be described as a mechanical simulation of the
interactions of objects at real-world scales. We are dealing with Newtonian
mechanics; that is, the well-understood laws of motion, popularized by Sir
Isaac Newton, that describe the behavior of objects under the influences of
other objects and external forces. Since then we’ve discovered that these laws
break down at very small (i.e. subatomic) and very large (i.e. planetary) scales.
New physics systems have been devised to work with these scales (for example,
relativistic and quantum), but these are beyond the scope of the reactor physics
engine. The Havok physics simulation technology works at the scale of objects
we interact with on a daily basis, such as chairs, cars, buildings, and footballs.
By default, the engine works in units of meters and kilograms.
It's important to keep in mind the scale in which you're working. For example,
a common mistake people make is to start by creating a cube 100 meters on
a side, and then they wonder why it takes so long to fall. A box of this size
when viewed at a distance sufficient to be able to see the entire box (say 1km
away) will appear to fall at the same speed as an aircraft hangar dropped from
a height and viewed from a kilometer away: slowly.
Changing Scale
The Havok physics engine does not care what units of measurement you use
when specifying the size of objects or the strength of gravity; it cares only
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