Game Development Reference
In-Depth Information
Figure 5-18.
A tilt in the spin axis causes the ball to curve.
Summary: Adding Spin Effects to the Projectile
Trajectory Model
In this section, you learned that a spinning object develops a lifting force known as Magnus
force. The magnitude of Magnus force is proportional to the rate at which the object is spinning,
and the direction of Magnus force is perpendicular to the flow velocity and spin axis. A general
expression for the Magnus force generated by an arbitrarily shaped object is difficult to derive,
but force expressions have been developed for cylindrical and spherical objects if certain
modeling simplifications are made. Here are some general concepts to keep in mind about the
effects of spin:
•
An object given backspin will generate a lifting force. An object given topspin will
generate a force that will push the object downwards.
•
The acceleration that results from Magnus force is inversely proportional to mass.
A heavier object will experience less acceleration than a similar, lighter object.
•
The magnitude of Magnus force depends on the geometry. All other things being equal,
larger objects will generate a larger Magnus force than will smaller objects.
