leapjs/lib/interaction_box.js

JavaScript client for the Leap Motion Controller

var glMatrix = require("gl-matrix")
  , vec3 = glMatrix.vec3;

/**
 * Constructs a InteractionBox object.
 *
 * @class InteractionBox
 * @memberof Leap
 * @classdesc
 * The InteractionBox class represents a box-shaped region completely within
 * the field of view of the Leap Motion controller.
 *
 * The interaction box is an axis-aligned rectangular prism and provides
 * normalized coordinates for hands, fingers, and tools within this box.
 * The InteractionBox class can make it easier to map positions in the
 * Leap Motion coordinate system to 2D or 3D coordinate systems used
 * for application drawing.
 *
 * ![Interaction Box](images/Leap_InteractionBox.png)
 *
 * The InteractionBox region is defined by a center and dimensions along the x, y, and z axes.
 */
var InteractionBox = module.exports = function(data) {
  /**
   * Indicates whether this is a valid InteractionBox object.
   *
   * @member valid
   * @type {Boolean}
   * @memberof Leap.InteractionBox.prototype
   */
  this.valid = true;
  /**
   * The center of the InteractionBox in device coordinates (millimeters).
   * This point is equidistant from all sides of the box.
   *
   * @member center
   * @type {number[]}
   * @memberof Leap.InteractionBox.prototype
   */
  this.center = data.center;

  this.size = data.size;
  /**
   * The width of the InteractionBox in millimeters, measured along the x-axis.
   *
   * @member width
   * @type {number}
   * @memberof Leap.InteractionBox.prototype
   */
  this.width = data.size[0];
  /**
   * The height of the InteractionBox in millimeters, measured along the y-axis.
   *
   * @member height
   * @type {number}
   * @memberof Leap.InteractionBox.prototype
   */
  this.height = data.size[1];
  /**
   * The depth of the InteractionBox in millimeters, measured along the z-axis.
   *
   * @member depth
   * @type {number}
   * @memberof Leap.InteractionBox.prototype
   */
  this.depth = data.size[2];
}

/**
 * Converts a position defined by normalized InteractionBox coordinates
 * into device coordinates in millimeters.
 *
 * This function performs the inverse of normalizePoint().
 *
 * @method denormalizePoint
 * @memberof Leap.InteractionBox.prototype
 * @param {number[]} normalizedPosition The input position in InteractionBox coordinates.
 * @returns {number[]} The corresponding denormalized position in device coordinates.
 */
InteractionBox.prototype.denormalizePoint = function(normalizedPosition) {
  return vec3.fromValues(
    (normalizedPosition[0] - 0.5) * this.size[0] + this.center[0],
    (normalizedPosition[1] - 0.5) * this.size[1] + this.center[1],
    (normalizedPosition[2] - 0.5) * this.size[2] + this.center[2]
  );
}

/**
 * Normalizes the coordinates of a point using the interaction box.
 *
 * Coordinates from the Leap Motion frame of reference (millimeters) are
 * converted to a range of [0..1] such that the minimum value of the
 * InteractionBox maps to 0 and the maximum value of the InteractionBox maps to 1.
 *
 * @method normalizePoint
 * @memberof Leap.InteractionBox.prototype
 * @param {number[]} position The input position in device coordinates.
 * @param {Boolean} clamp Whether or not to limit the output value to the range [0,1]
 * when the input position is outside the InteractionBox. Defaults to true.
 * @returns {number[]} The normalized position.
 */
InteractionBox.prototype.normalizePoint = function(position, clamp) {
  var vec = vec3.fromValues(
    ((position[0] - this.center[0]) / this.size[0]) + 0.5,
    ((position[1] - this.center[1]) / this.size[1]) + 0.5,
    ((position[2] - this.center[2]) / this.size[2]) + 0.5
  );

  if (clamp) {
    vec[0] = Math.min(Math.max(vec[0], 0), 1);
    vec[1] = Math.min(Math.max(vec[1], 0), 1);
    vec[2] = Math.min(Math.max(vec[2], 0), 1);
  }
  return vec;
}

/**
 * Writes a brief, human readable description of the InteractionBox object.
 *
 * @method toString
 * @memberof Leap.InteractionBox.prototype
 * @returns {String} A description of the InteractionBox object as a string.
 */
InteractionBox.prototype.toString = function() {
  return "InteractionBox [ width:" + this.width + " | height:" + this.height + " | depth:" + this.depth + " ]";
}

/**
 * An invalid InteractionBox object.
 *
 * You can use this InteractionBox instance in comparisons testing
 * whether a given InteractionBox instance is valid or invalid. (You can also use the
 * InteractionBox.valid property.)
 *
 * @static
 * @type {Leap.InteractionBox}
 * @name Invalid
 * @memberof Leap.InteractionBox
 */
InteractionBox.Invalid = { valid: false };