// TODO // cross and scale return new vectors, // whereas add and normalize operate in-place
function d3_geo_cartesian(spherical) {
var λ = spherical[0], φ = spherical[1], cosφ = Math.cos(φ); return [ cosφ * Math.cos(λ), cosφ * Math.sin(λ), Math.sin(φ) ];
}
function d3_geo_cartesianDot(a, b) {
return a[0] * b[0] + a[1] * b[1] + a[2] * b[2];
}
function d3_geo_cartesianCross(a, b) {
return [ a[1] * b[2] - a[2] * b[1], a[2] * b[0] - a[0] * b[2], a[0] * b[1] - a[1] * b[0] ];
}
function d3_geo_cartesianAdd(a, b) {
a[0] += b[0]; a[1] += b[1]; a[2] += b[2];
}
function d3_geo_cartesianScale(vector, k) {
return [ vector[0] * k, vector[1] * k, vector[2] * k ];
}
function d3_geo_cartesianNormalize(d) {
var l = Math.sqrt(d[0] * d[0] + d[1] * d[1] + d[2] * d[2]); d[0] /= l; d[1] /= l; d[2] /= l;
}