anchor.diff:  }
   
   class PointLight extends Light {
  -  VM.Vector3 _pos;
  +  VM.Vector3 pos;
     VM.Vector3 _colDiffuse;
     VM.Vector3 _colSpecular;
     double _range;
     double _glossiness;
   
  -  PointLight(String name, this._pos, this._colDiffuse, this._colSpecular,
  +  PointLight(String name, this.pos, this._colDiffuse, this._colSpecular,
         this._range, this._glossiness)
         : super(name, lightTypePoint);
   
     // Must be in sync with UnpackPointLightInfo
     @override
     void ExtractInfo(Float32List m, int o) {
  -    m[o + 0] = _pos.x;
  -    m[o + 1] = _pos.y;
  -    m[o + 2] = _pos.z;
  +    m[o + 0] = pos.x;
  +    m[o + 1] = pos.y;
  +    m[o + 2] = pos.z;
       //
       m[o + 8] = _colDiffuse.x;
       m[o + 9] = _colDiffuse.y;
  
positive.code: }
  
  class SpotLight extends Light {
    VM.Vector3 _pos;
    VM.Vector3 dir;
    VM.Vector3 _colDiffuse;
    VM.Vector3 _colSpecular;
  
negative.code: 
    SpotLight(
        String name,
        VM.Vector3 this.pos,
        VM.Vector3 this.dir,
        this._colDiffuse,
        this._colSpecular,
  