isomer/js/point.js

A simple isometric graphics library for HTML5 canvas

function Point(x, y, z) {
  if (this instanceof Point) {
    this.x = (typeof x === 'number') ? x : 0;
    this.y = (typeof y === 'number') ? y : 0;
    this.z = (typeof z === 'number') ? z : 0;
  } else {
    return new Point(x, y, z);
  }
}


Point.ORIGIN = new Point(0, 0, 0);


/**
 * Translate a point from a given dx, dy, and dz
 */
Point.prototype.translate = function(dx, dy, dz) {

  dx = (typeof dx === 'number') ? dx : 0;
  dy = (typeof dy === 'number') ? dy : 0;
  dz = (typeof dz === 'number') ? dz : 0;

  return new Point(
    this.x + dx,
    this.y + dy,
    this.z + dz);
};


/**
 * Scale a point about a given origin
 */
Point.prototype.scale = function(origin, dx, dy, dz) {
  var p = this.translate(-origin.x, -origin.y, -origin.z);

  if (dy === undefined && dz === undefined) {
    /* If both dy and dz are left out, scale all coordinates equally */
    dy = dz = dx;
    /* If just dz is missing, set it equal to 1 */
  } else {
    dz = (typeof dz === 'number') ? dz : 1;
  }

  p.x *= dx;
  p.y *= dy;
  p.z *= dz;

  return p.translate(origin.x, origin.y, origin.z);
};

/**
 * Rotate about origin on the X axis
 */
Point.prototype.rotateX = function(origin, angle) {
  var p = this.translate(-origin.x, -origin.y, -origin.z);

  var z = p.z * Math.cos(angle) - p.y * Math.sin(angle);
  var y = p.z * Math.sin(angle) + p.y * Math.cos(angle);
  p.z = z;
  p.y = y;

  return p.translate(origin.x, origin.y, origin.z);
};

/**
 * Rotate about origin on the Y axis
 */
Point.prototype.rotateY = function(origin, angle) {
  var p = this.translate(-origin.x, -origin.y, -origin.z);

  var x = p.x * Math.cos(angle) - p.z * Math.sin(angle);
  var z = p.x * Math.sin(angle) + p.z * Math.cos(angle);
  p.x = x;
  p.z = z;

  return p.translate(origin.x, origin.y, origin.z);
};

/**
 * Rotate about origin on the Z axis
 */
Point.prototype.rotateZ = function(origin, angle) {
  var p = this.translate(-origin.x, -origin.y, -origin.z);

  var x = p.x * Math.cos(angle) - p.y * Math.sin(angle);
  var y = p.x * Math.sin(angle) + p.y * Math.cos(angle);
  p.x = x;
  p.y = y;

  return p.translate(origin.x, origin.y, origin.z);
};


/**
 * The depth of a point in the isometric plane
 */
Point.prototype.depth = function() {
  /* z is weighted slightly to accomodate |_ arrangements */
  return this.x + this.y - 2 * this.z;
};


/**
 * Distance between two points
 */
Point.distance = function(p1, p2) {
  var dx = p2.x - p1.x;
  var dy = p2.y - p1.y;
  var dz = p2.z - p1.z;

  return Math.sqrt(dx * dx + dy * dy + dz * dz);
};


module.exports = Point;