Game Development Reference
ing, it just floats in the water, bobbing up and down. However, when the boat begins
traveling at high speed, the force of the water hitting the bottom of the boat causes the
boat to rise up. This is known as planing, and it greatly reduces the resistance of the
vessel. Semi-displacement vessels are those that straddle the two categories, with some
support coming from buoyancy and some coming from planing forces. Before we con‐
tinue discussing this, let's go over some vocabulary.
The hull of the ship is the watertight part of the ship that actually displaces the water.
Everything in or on the ship is contained within the hull, which is partially submerged
in the water. The length of the ship is the distance measured from the bow to the stern.
In practice, there are several lengths used to denote the length of a ship, but here we'll
refer to the overall length of the hull. The bow is the front of the ship, while the stern is
the aft part. When you are on the ship facing the bow, the port side is to your left and
the starboard side is to your right. The overall height of the hull is called the depth , and
its width is called breadth or beam . When a ship is floating in the water, the distance
from the water surface to the bottom of the hull is called the draft . Figure 16-1 illustrates
Figure 16-1. Ship geometry
Given that ship design is a diverse subject, we'll limit ourselves to discussing those
aspects of ships that make for realistic models. These subjects include stability and
sinking, resistance characteristics, propulstion, and manuverability. Most of these sub‐
jects cannot be fully simulated in real time, so we'll show you some general rules that
ships follow instead of full numerical simulation.