vector4 sample_hypersphere_cone(vector4 center, float maxangle, vector4 u)
Direction in the center of the cone. This does not need to be normalized.
Maximum angle, in radians, away from
center that any sample of the cone
will be, so long as all
u values are between 0 and 1.
Four numbers between 0 and 1.
Returns a vector4 of length < 1, based on
Given uniform random
u vectors of four values in [0,1), the returned vectors will be
uniform random and continuous with respect to
u inside the unit hypersphere,
in the hypervolume within
maxangle of the direction indicated by