/* Fake a Flog.* namespace */
  if(typeof(Flog) == 'undefined') var Flog = {};
  if(typeof(Flog.RayTracer) == 'undefined') Flog.RayTracer = {};
  if(typeof(Flog.RayTracer.Shape) == 'undefined') Flog.RayTracer.Shape = {};
  
  Flog.RayTracer.Shape.Plane = Class.create();
  
  Flog.RayTracer.Shape.Plane.prototype = {
      d: 0.0,
      
      initialize : function(pos, d, material) {
          this.position = pos;
          this.d = d;
          this.material = material;
      },
      
      intersect: function(ray){
          var info = new Flog.RayTracer.IntersectionInfo();
          
          var Vd = this.position.dot(ray.direction);
          if(Vd == 0) return info; // no intersection
          
          var t = -(this.position.dot(ray.position) + this.d) / Vd;
          if(t <= 0) return info;
  
          info.shape = this;
          info.isHit = true;      
          info.position = Flog.RayTracer.Vector.prototype.add(
                                              ray.position, 
                                              Flog.RayTracer.Vector.prototype.multiplyScalar(
                                                  ray.direction,
                                                  t
                                              )
                                          );
          info.normal = this.position;
          info.distance = t;
          
          if(this.material.hasTexture){
              var vU = new Flog.RayTracer.Vector(this.position.y, this.position.z, -this.position.x);
              var vV = vU.cross(this.position);
              var u = info.position.dot(vU);
              var v = info.position.dot(vV);
              info.color = this.material.getColor(u,v);
          } else {
              info.color = this.material.getColor(0,0);
          }
          
          return info;
      },
          
      toString : function () {
          return 'Plane [' + this.position + ', d=' + this.d + ']';   
      }
  }