greiner-hormann/src/intersection.js

Greiner-Hormann clipping algorithm

export default class Intersection {


  /**
   * @param {Vertex} s1
   * @param {Vertex} s2
   * @param {Vertex} c1
   * @param {Vertex} c2
   */
  constructor(s1, s2, c1, c2) {

    /**
     * @type {Number}
     */
    this.x = 0.0;

    /**
     * @type {Number}
     */
    this.y = 0.0;

    /**
     * @type {Number}
     */
    this.toSource = 0.0;

    /**
     * @type {Number}
     */
    this.toClip = 0.0;

    const d = (c2.y - c1.y) * (s2.x - s1.x) - (c2.x - c1.x) * (s2.y - s1.y);

    if (d === 0) return;

    /**
     * @type {Number}
     */
    this.toSource = ((c2.x - c1.x) * (s1.y - c1.y) - (c2.y - c1.y) * (s1.x - c1.x)) / d;

    /**
     * @type {Number}
     */
    this.toClip = ((s2.x - s1.x) * (s1.y - c1.y) - (s2.y - s1.y) * (s1.x - c1.x)) / d;

    if (this.valid()) {
        this.x = s1.x + this.toSource * (s2.x - s1.x);
        this.y = s1.y + this.toSource * (s2.y - s1.y);
    }
  }


  /**
   * @return {Boolean}
   */
  valid () {
      return (0 < this.toSource && this.toSource < 1) && (0 < this.toClip && this.toClip < 1);
  }
}