utils.cc File Reference

This file contains utility function implementations. More...

#include "lsst/sphgeom/utils.h"
#include <cmath>
#include "lsst/sphgeom/UnitVector3d.h"

Functions
double	lsst::sphgeom::getMinSquaredChordLength (Vector3d const &v, Vector3d const &a, Vector3d const &b, Vector3d const &n)
double	lsst::sphgeom::getMaxSquaredChordLength (Vector3d const &v, Vector3d const &a, Vector3d const &b, Vector3d const &n)
Vector3d	lsst::sphgeom::getWeightedCentroid (UnitVector3d const &v0, UnitVector3d const &v1, UnitVector3d const &v2)

Detailed Description

This file contains utility function implementations.

Function Documentation

getMaxSquaredChordLength()

double lsst::sphgeom::getMaxSquaredChordLength	(	Vector3d const &	v,
		Vector3d const &	a,
		Vector3d const &	b,
		Vector3d const &	n
	)

Let p be the unit vector furthest from v that lies on the plane with normal n in the direction of the cross product of a and b. If p is in the interior of the great circle segment from a to b, then this helper function returns the squared chord length between p and v. Otherwise it returns 0 - the minimum squared chord length between any pair of points on the sphere.

getMinSquaredChordLength()

double lsst::sphgeom::getMinSquaredChordLength	(	Vector3d const &	v,
		Vector3d const &	a,
		Vector3d const &	b,
		Vector3d const &	n
	)

Let p be the unit vector closest to v that lies on the plane with normal n in the direction of the cross product of a and b. If p is in the interior of the great circle segment from a to b, then this function returns the squared chord length between p and v. Otherwise it returns 4 - the maximum squared chord length between any pair of points on the unit sphere.

getWeightedCentroid()

Vector3d lsst::sphgeom::getWeightedCentroid	(	UnitVector3d const &	v0,
		UnitVector3d const &	v1,
		UnitVector3d const &	v2
	)

getWeightedCentroid returns the center of mass of the given spherical triangle (assuming a uniform mass distribution over the triangle surface), weighted by the triangle area.