polygon-tools/lib/vec.js

Polygon tools

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.cross = cross;
exports.length = length;
exports.dot = dot;
exports.normalize = normalize;
exports.add = add;
exports.subtract = subtract;
/**
 * @module vec
 */

/**
 * Cross product
 *
 * @param {Array} a First vector
 * @param {Array} b Second vector
 *
 * @return {Array}
 */
function cross(a, b) {
  a = a.length === 2 ? [a[0], a[1], 0] : a;
  b = b.length === 2 ? [b[0], b[1], 0] : 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]];
}

/**
 * Length of vector
 *
 * @param {Array} v Vector
 *
 * @return {Number}
 */
function length(v) {
  return Math.sqrt(v.slice(0, 3).reduce(function (p, w, i) {
    return p + w * w;
  }, 0));
}

/**
 * Dot product
 *
 * @param {Array} a Vector
 * @param {Array} b Vector
 *
 * @return {Number}
 */
function dot(a, b) {
  return a.reduce(function (p, v, i) {
    return p + v * b[i];
  }, 0);
}

/**
 * Normalize a vector
 *
 * @param {Array} v Vector
 *
 * @return {Array}
 */
function normalize(v) {
  var len = length(v);
  return v.slice(0, 3).map(function (i) {
    return i / len;
  });
}

/**
 * Add
 *
 * @param {Array} a First vector
 * @param {Array} b Second vector
 *
 * @return {Array}
 */
function add(a, b) {
  return a.slice(0, 3).map(function (v, i) {
    return v + b[i];
  });
}

/**
 * Subtract
 *
 * @param {Array} a First vector
 * @param {Array} b Second vector
 *
 * @return {Array}
 */
function subtract(a, b) {
  return a.slice(0, 3).map(function (v, i) {
    return v - b[i];
  });
}

var sub = exports.sub = subtract;