Point3D lerp(Point3D p2, num coeff)

Performs a linear interpolation between two points.

Source 

Point3D lerp(Point3D p2, num coeff) {
  return new Point3D(
      this.x * coeff + p2.x * (1-coeff),
      this.y * coeff + p2.y * (1-coeff),
      this.z * coeff + p2.z * (1-coeff)
  );
}