/* 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.Sphere = Class.create();
  
  Flog.RayTracer.Shape.Sphere.prototype = {
      initialize : function(pos, radius, material) {
          this.radius = radius;
          this.position = pos;
          this.material = material;
      },
      
      intersect: function(ray){
          var info = new Flog.RayTracer.IntersectionInfo();
          info.shape = this;
          
          var dst = Flog.RayTracer.Vector.prototype.subtract(ray.position, this.position);
          
          var B = dst.dot(ray.direction);
          var C = dst.dot(dst) - (this.radius * this.radius);
          var D = (B * B) - C;
          
          if(D > 0){ // intersection!
              info.isHit = true;
              info.distance = (-B) - Math.sqrt(D);
              info.position = Flog.RayTracer.Vector.prototype.add(
                                                  ray.position, 
                                                  Flog.RayTracer.Vector.prototype.multiplyScalar(
                                                      ray.direction,
                                                      info.distance
                                                  )
                                              );
              info.normal = Flog.RayTracer.Vector.prototype.subtract(
                                              info.position,
                                              this.position
                                          ).normalize();
              
              info.color = this.material.getColor(0,0);
          } else {
              info.isHit = false;
          }
          return info;
      },
          
      toString : function () {
          return 'Sphere [position=' + this.position + ', radius=' + this.radius + ']';   
      }
  }