vector2 sample_circle_slice(vector2 center, float maxangle, vector2 u)
Direction in the center of the slice. This does not need to be normalized.
Maximum angle, in radians, away from
center that any sample of the slice
will be, so long as all
u values are between 0 and 1.
Pair of numbers between 0 and 1.
Returns a vector2 of length < 1, based on
Given uniform random
u pairs of values in [0,1), the returned vectors will be
uniform random and continuous with respect to
u inside the unit circle,
in the slice within
maxangle of the direction indicated by