anchor.diff:  }
   
   class SpotLight extends Light {
  -  VM.Vector3 _pos;
  +  VM.Vector3 pos;
     VM.Vector3 dir;
     VM.Vector3 _colDiffuse;
     VM.Vector3 _colSpecular;
  
positive.code: 
    SpotLight(
        String name,
        VM.Vector3 this._pos,
        VM.Vector3 this.dir,
        this._colDiffuse,
        this._colSpecular,
  
negative.code:   // Must be in sync with UnpackSpotLightInfo
    @override
    void ExtractInfo(Float32List m, int o) {
      m[o + 0] = pos.x;
      m[o + 1] = pos.y;
      m[o + 2] = pos.z;
      //
      m[o + 4] = dir.x;
      m[o + 5] = dir.y;
  