Intersection intersect(Ray r, num prevBestDistance)

Performs a ray - primitive intersection test. Returns an Intersection object with the associated information.

If the ray did not hit the primitive, the distance will be negative.

Source 

Intersection intersect(Ray r, num prevBestDistance) {
  Intersection intersect = new Intersection();

  // perform calculations in homogeneous space
  // check if ray is orthogonal to normal (= parallel to plane)
  Vector4 homDir = new Vector4(r.direction.x, r.direction.y, r.direction.z, 0.0);
  double div = homDir.dot(equation);

  if (div.abs() > EPS) {
    // calculate distance from ray origin to plane
    // use homogeneous vector4 representation
    Vector4 vec4 = -(r.origin.xyzz..w = 1.0);
    var dist = vec4.dot(equation) / div;

    intersect.distance = dist;
    intersect.prim = this;
    intersect.hitPoint = r.getPoint3(dist);
  }

  return intersect;
}