// Adds a simple cube at a specified location in the maze grid
        void AddWall(int row, int col, float height, BasicColor color)
        {

            // TT Oct-2006 - Add an option to use a sphere instead of a cube
            if (_UseSphere[(byte)color])
            {
                SphereShapeProperties cSphereShape = null;
                SingleShapeEntity sphere = null;
                float radius;

                radius = _state.SphereScale *  height / 2.0f;

                // create simple entity, with a single shape
                cSphereShape = new SphereShapeProperties(
                    // TT -- Change to infinite mass so that the walls
                    // do not "blow apart" if you bump them!
                    // TT Oct 2006 -- Allow user to specify this
                        _WallMasses[(byte)color], // mass in kilograms.
                        new Pose(),     // relative pose
                        radius);    // radius
                cSphereShape.Material = new MaterialProperties("gsphere", 1.0f, 0.01f, 0.01f);
                // Set the color of the sphere according to the bitmap image
                // or the specified color if no bitmap
                if (_WallTextures[(byte)color] == "")
                {
                    // TT - Changed for October CTP because DiffuseColor
                    // is a Vector4, but my WallColors are Vector3
                    //cBoxShape.DiffuseColor = _WallColors[(byte)color];
                    cSphereShape.DiffuseColor.X = (float)(_WallColors[(byte)color].X / 255.0);
                    cSphereShape.DiffuseColor.Y = (float)(_WallColors[(byte)color].Y / 255.0);
                    cSphereShape.DiffuseColor.Z = (float)(_WallColors[(byte)color].Z / 255.0);
                    cSphereShape.DiffuseColor.W = 1.0f;
                }
                else
                    cSphereShape.TextureFileName = _WallTextures[(byte)color];

                sphere = new SingleShapeEntity(new SphereShape(cSphereShape),
                    new Vector3((col * -_state.GridSpacing),
                            radius,
                            -(row * _state.GridSpacing)));

                // Name the entity. All entities must have unique names
                sphere.State.Name = "ball_" + row + "_" + col;

                // Insert entity in simulation.  
                _simEnginePort.Insert(sphere);
            }
            else
            {
                // Dimensions are in meters
                Vector3 dimensions =
                    new Vector3(_state.WallBoxSize * _state.GridSpacing,
                            height * _state.HeightScale,
                            _state.WallBoxSize * _state.GridSpacing);
                BoxShapeProperties cBoxShape = null;
                SingleShapeEntity box = null;

                // create simple immovable entity, with a single shape
                cBoxShape = new BoxShapeProperties(
                    // TT -- Change to infinite mass so that the walls
                    // do not "blow apart" if you bump them!
                    // TT Oct 2006 -- Allow user to specify this
                        _WallMasses[(byte)color], // mass in kilograms.
                        new Pose(),     // relative pose
                        dimensions);    // dimensions
                cBoxShape.Material = new MaterialProperties("gbox", 1.0f, 0.4f, 0.5f);
                // Set the color of the box according to the bitmap image
                // or the specified color if no bitmap
                if (_WallTextures[(byte)color] == "")
                {
                    // TT - Changed for October CTP because DiffuseColor
                    // is a Vector4, but my WallColors are Vector3
                    //cBoxShape.DiffuseColor = _WallColors[(byte)color];
                    cBoxShape.DiffuseColor.X = (float)(_WallColors[(byte)color].X / 255.0);
                    cBoxShape.DiffuseColor.Y = (float)(_WallColors[(byte)color].Y / 255.0);
                    cBoxShape.DiffuseColor.Z = (float)(_WallColors[(byte)color].Z / 255.0);
                    cBoxShape.DiffuseColor.W = 0.5f;
                }
                else
                    cBoxShape.TextureFileName = _WallTextures[(byte)color];

                box = new SingleShapeEntity(new BoxShape(cBoxShape),
                    new Vector3(col * -_state.GridSpacing,
                            height * _state.HeightScale / 2,
                            -(row * _state.GridSpacing)));

                // Name the entity. All entities must have unique names
                box.State.Name = "wall_" + row + "_" + col;

                // Insert entity in simulation.  
                _simEnginePort.Insert(box);
            }

            BlockCounter++;
        }