Generates a convex hull of a two-angle grid for 2D surface plotting.
Two-angle spherical grids may be used for plotting direction dependence of some property, for example singlet yield in spin chemistry. This requires surface triangle information, which this function would generate.
theta_angles - a column vector of theta angles, polar coordinates, ISO convention, radians phi_angles - a column vector of phi angles, polar coordinates, ISO convention, radians
hull - a matrix of point indices of dimension Nx3, where N is the number of triangular facets
Singlet yield anisotropy calculations in the spin chemistry example set make use of the hull information for Lebedev grids.
Hulls can only be generated for two-angle spherical grids.
Version 1.10, authors: Ilya Kuprov