Routine to convert the position angles $(\theta,\phi)$ of a point on the sphere into its 3D position vector (x,y,z) with $x = \sin\theta\cos\phi$ , $y=\sin\theta\sin\phi$ , $z=\cos\theta$ .

Location in HEALPix directory tree: src/f90/mod/pix_tools.f90

FORMAT

call ang2vec( theta, phi, vector )

name & dimensionality	kind	in/out	description

theta	DP	IN	colatitude in radians measured southward from north pole (in $[0,\ \pi]$ ).
phi	DP	IN	longitude in radians measured eastward (in $[0,\ 2\pi]$ ).
vector(3)	DP	OUT	three dimensional cartesian position vector (x,y,z) normalised to unity. The north pole is (0,0,1)