Game Development Reference
In-Depth Information
Just as was the case with drag and wind, spin can have a significant effect on the flight of a
golf ball. Two golf ball trajectories are shown in Figure 5-17. The first trajectory is computed for
a golf ball with a 300
rad/s
backspin. The golf ball travels a distance of 170.5
m
. The second golf
ball has identical input parameters as the first except that the spin is set to zero. Without the lift
caused by the backspin, the ball only travels 154.3
m
. Since distance per shot is an important
element of golf, you can see why putting the proper spin on the ball is very important.
Figure 5-17.
The effect of spin on golf ball flight
Another interesting effect that spin can have on a golf ball is if the spin axis is tilted so that
it isn't parallel to one of the coordinate axes. When the axis is tilted, there will be Magnus force
components in all three directions, and the golf ball trajectory will curve in the horizontal
direction. To see an example of this effect, look at the trajectory shown in Figure 5-18. The view
has been switched to the x-y plane, so we are looking at the trajectory from above. The spin axis
in this case was tilted at a 45-degree angle in the y-z plane. Even though the initial y-velocity
was zero, the ball begins to curve to the right in what is called in the golf world a “slice.” If the
spin axis had been tilted a negative 45 degrees in the y-z plane, the golf ball would have curved
to the left in a shot known as a “hook.”
