double v = 1. - u;
this->horz_radius = u*prev.horz_radius + v*next.horz_radius;
this->vert_radius = u*prev.vert_radius + v*next.vert_radius;
double v = 1. - u;
this->horz_radius = u*prev.horz_radius + v*next.horz_radius;
this->vert_radius = u*prev.vert_radius + v*next.vert_radius;