1% A dumbbell: radius 1 - waist*sin(theta)^2, stretched along z. 3function [gx, gy, gz] = shape(theta, phi, waist, stretch) 5 r = 1 - waist * (st .^ 2); 6 gx = r .* (st .* cos(phi)); 7 gy = r .* (st .* sin(phi)); 8 gz = (1 + stretch) * (r .* cos(theta));