Loops the value t, so that it is never larger than length and never smaller than 0.
This is similar to the modulo operator but it works with floating point numbers. For example, using 3.0 for
t and 2.5 for
length, the result would be 0.5. With
t = 5 and
length = 2.5, the result would be 0.0. Note, however, that the behaviour is not defined for negative numbers as it is for the modulo operator.
In the example below the value of time is restricted between 0.0 and just under 3.0. This is then used to keep the x position in this range.