anchor.diff:      return _vertices.length ~/ 3;
     }
   
  +  Float32List GetAttribute(String canonical) {
  +    return _attributes[canonical];
  +  }
  +
     void AddAttribute(String canonical, Float32List data, int width) {
       assert(data.length ~/ width == _vertices.length ~/ 3);
       _addBuffer(canonical, data);
  
positive.code:   }
  
    void AddVertices(Float32List data) {
      _addBuffer(aVertexPosition, data);
      _vertices = data;
    }
  
  
negative.code:     return _attributes.keys;
    }
  
    @override
    String toString() {
      List<String> lst = ["Faces:${_faces.length}"];
      for (String c in _attributes.keys) {
        lst.add("${c}:${_attributes[c].length}");
      }
  
      return "MESH[${name}] " + lst.join("  ");
    }
  }
  
  void _GeometryBuilderAttributesToMeshData(GeometryBuilder gb, MeshData md) {
  