//Thanks to en.wikipedia.org/wiki/…
  void rotateAtAround(float angle, PVector axis) {
    PVector buffer = new PVector(0,0,0);
    axis.normalize();
    buffer.x = this.endPoint.x*( cos(angle) +     pow(axis.x,2) *  ( 1-cos(angle) ) )
             + this.endPoint.y*( axis.x*axis.y*( 1-cos(angle) ) - axis.z*sin(angle) )
             + this.endPoint.z*( axis.x*axis.z*( 1-cos(angle) ) + axis.y*sin(angle) );

    buffer.y = this.endPoint.x*( axis.y*axis.x*( 1-cos(angle) ) + axis.z*sin(angle) )

float x = rand();
if (x < 1/3) rotateX(whatever);
else if (x < 2/3) rotateY(whatever);
else rotateZ(whatever);