Graphics Programs Reference
In-Depth Information
to stabilize their landing. In the same way, a cape on a jumping character will continue to
move even after the character lands.
The axe tutorial in Chapter 8 will give you a chance to implement these two concepts.
Physics
In Chapter 12, “Maya Dynamics and Effects,” you'll see that one of Maya's most powerful
features is its ability to simulate the dynamics of moving objects. To use that capability
effectively, you need a general awareness of the properties of physics—how objects behave
in the physical world.
newton's Laws of Motion
You need to know three basic laws of motion. Sir Isaac Newton set forth these three laws,
summarized here. Everyone in animation needs to understand the first two laws, because
they play a large part in how animations should look. Coming to terms with the third is
an art:
An object in motion will remain in motion, and an object at rest will remain at rest
unless an external force acts upon the object. This is called inertia , and understand-
ing it is critical to good animation. You'll find more on this in Chapters 8 and 9.
The more massive an object is, the more force is needed to accelerate or decelerate its
motion. This law deals with an object's momentum .
Every action has an equal and opposite reaction. When you press on a brick wall,
for example, the wall exerts an equal amount of force on your hand. That way, your
hand doesn't smash through the wall.
Momentum
It's important to understand what momentum is all about. When an object is in motion,
it has momentum. The amount of momentum is calculated by multiplying the mass of
the object by its velocity. The heavier something is, or the faster it's moving, the more
momentum it has, and the bigger the bruise it will leave if it hits you. Duck!
That's why a tiny pebble on the highway can cause such a significant impact on your
windshield, for example. Its sheer speed greatly increases its momentum. Likewise, a
slow-moving garbage truck can bash your car, relying on its sheer mass for its tremen-
dous momentum.
When one moving object meets another object—moving or not—momentum is
transferred between them. So, when something hits an object, that object is moved if
sufficient momentum is transferred to it. For more on this notion, see the axe-throwing
exercise in Chapter 8.
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