Game Development Reference
In-Depth Information
its right side (known as the right rail), and the board will curve to the right. As a general rule, the
longer and heavier the surfboard, the slower and harder it is to turn.
Coming up with an analytical model for the turn of a surfboard requires an estimation of
the drag acting on the board. Modeling the drag of a surfboard is a difficult problem because the
wetted area of the board and the drag coefficient will change as the surfer changes his position
on the board and the board rotates up or down. One way to approximate drag in a game simu-
lation is to assume that the drag when the surfer is in a neutral position on the board balances
the forward force on the board so the velocity of the surfer matches the velocity of the wave.
Summary
In this chapter, we went nautical and saw some basic physics about boats and things that float.
Starting with basic Newtonian mechanics and kinematics, we explored how to model the forces
that result in the acceleration and velocity of boats, jet skis, and surfboards. We discussed
buoyancy, the force that keeps things afloat. Some of the specific things covered in the chapter
include the following:
•
The different types of ship hulls including displacement, semi-displacement, and
planing hulls
•
The basic forces that act on a boat—gravity, buoyancy, thrust, and drag
•
How an boat engine works and how power is transferred from the engine to the propeller
to generate thrust
•
The different drag forces experienced by a boat including skin friction, wave, form, and
aerodynamic drag
•
How an acceleration profile for a boat or other watercraft can be obtained from perfor-
mance test data
•
An introduction to the physics of surfing including the forces and moments that act
upon a surfboard
Answers to Exercises
1.
The maximum buoyancy force that can be exerted on the canoe is equal to the volume
of the canoe multiplied by the density of water.
F
=
r
g
=
1000 * 0.5*
g
=
500
g
B
w
c
Since the canoe itself weighs 30
kg
, an additional 470
kg
can be loaded into it before it
will sink. In real life, however, you would never want to load a boat to its theoretical
buoyancy limit.
