There are many situations where we don't know the exact position of an object at a given time, but we do know an equation that describes its movement. These equations are known as parametric curves; they are parametric because the position depends on one parameter—for example, the time.
There are many examples of parametric curves. For example, a projectile shot in a game, a car going downhill, or a bouncing ball. In each case, there are equations that describe the motion of these objects under ideal conditions. The following diagram shows the parametric equation that describes the free-fall motion:
Where:
: Gravity at 
: Initial velocity
: Initial Position
: Time
: Position
We are going to use parametric curves to animate objects in a WebGL scene. In this example, we will model a set of bouncing balls. The complete source code for this exercise...