void update_indicator(CreateDropPrimitiveButton button, FScene scene)
        {
            if (button == null || buttonTypes.ContainsKey(button) == false)
            {
                return;
            }
            SOType t = buttonTypes[button];

            if (t.hasTag(SOType.TagPrimitive) == false)
            {
                return;
            }

            scene.DefaultPrimitiveType = t;

            if (indicatorButton != null)
            {
                indicatorButton.RemoveGO(indicatorGO);
            }
            indicatorButton = button;

            indicatorGO.SetPosition(Vector3f.Zero);
            indicatorGO.SetRotation(Quaternionf.Identity);
            indicatorGO.SetLocalScale(fIndicatorSize * Vector3f.One);
            indicatorGO.SetLocalPosition(
                indicatorGO.GetLocalPosition() + fIndicatorShift * (Vector3f.AxisY - 1 * Vector3f.AxisZ + Vector3f.AxisX));

            indicatorButton.AppendNewGO(indicatorGO, indicatorButton.RootGameObject, false);
            indicatorGO.Show();
        }
        CreateDropPrimitiveButton add_curve_button(Cockpit cockpit, string sName, float fHUDRadius, float dx, float dy,
                                                   Material bgMaterial, Material primMaterial,
                                                   Func <TransformableSO> CreateCurveF
                                                   )
        {
            float fButtonRadius = 0.08f;

            CreateDropPrimitiveButton button = new CreateDropPrimitiveButton()
            {
                TargetScene     = cockpit.Scene,
                CreatePrimitive = CreateCurveF
            };

            button.Create(fButtonRadius, bgMaterial);
            //var gen = (customGenerator != null) ? customGenerator :
            //    new primitiveIconGenerator() { PrimType = primType, PrimMaterial = primMaterial, PrimSize = fButtonRadius * fPrimRadiusScale };
            //button.AddVisualElements(gen.Generate(), true);
            HUDUtil.PlaceInSphere(button, fHUDRadius, dx, dy);
            button.Name             = sName;
            button.OnDoubleClicked += (s, e) => {
                // [TODO] could have a lighter record here because we can easily recreate primitive...
                cockpit.Scene.History.PushChange(
                    new AddSOChange()
                {
                    scene = cockpit.Scene, so = CreateCurveF()
                });
                cockpit.Scene.History.PushInteractionCheckpoint();
            };
            return(button);
        }
        public void Create(Cockpit cockpit)
        {
            base.Create();

            float    fHUDRadius    = 0.7f;
            float    fButtonRadius = 0.08f;
            Color    bgColor       = new Color(0.7f, 0.7f, 1.0f, 0.7f);
            Material bgMaterial    = (bgColor.a == 1.0f) ?
                                     MaterialUtil.CreateStandardMaterial(bgColor) : MaterialUtil.CreateTransparentMaterial(bgColor);
            Material primMaterial = MaterialUtil.CreateStandardMaterial(Color.yellow);


            var addCylinderButton = add_primitive_button(cockpit, "addCylinder", fHUDRadius, -45.0f, 0.0f,
                                                         PrimitiveType.Cylinder, 0.7f, bgMaterial, primMaterial,
                                                         () => {
                return(new CylinderSO().Create(cockpit.Scene.DefaultSOMaterial));
            });

            AddChild(addCylinderButton);
            buttons.Add(addCylinderButton);
            buttonTypes[addCylinderButton] = SOTypes.Cylinder;


            var addBoxButton = add_primitive_button(cockpit, "addBox", fHUDRadius, -45.0f, -15.0f,
                                                    PrimitiveType.Cube, 0.7f, bgMaterial, primMaterial,
                                                    () => {
                return(new BoxSO().Create(cockpit.Scene.DefaultSOMaterial));
            });

            AddChild(addBoxButton);
            buttons.Add(addBoxButton);
            buttonTypes[addBoxButton] = SOTypes.Box;


            var addSphereButton = add_primitive_button(cockpit, "addSphere", fHUDRadius, -45.0f, -30.0f,
                                                       PrimitiveType.Sphere, 0.85f, bgMaterial, primMaterial,
                                                       () => {
                return(new SphereSO().Create(cockpit.Scene.DefaultSOMaterial));
            });

            AddChild(addSphereButton);
            buttons.Add(addSphereButton);
            buttonTypes[addSphereButton] = SOTypes.Sphere;


            var addPivotButton = add_primitive_button(cockpit, "addPivot", fHUDRadius, -60.0f, 0.0f,
                                                      PrimitiveType.Sphere, 0.7f, bgMaterial, primMaterial,
                                                      () => {
                return(new PivotSO().Create(cockpit.Scene.PivotSOMaterial, cockpit.Scene.FrameSOMaterial,
                                            FPlatform.WidgetOverlayLayer));
            },
                                                      new pivotIconGenerator()
            {
                SphereMaterial = cockpit.Scene.SelectedMaterial,
                FrameMaterial  = cockpit.Scene.FrameMaterial, PrimSize = fButtonRadius * 0.7f
            });

            AddChild(addPivotButton);
            buttons.Add(addPivotButton);
            buttonTypes[addPivotButton] = SOTypes.Pivot;


            //var addCurveButton = add_curve_button(cockpit, "addCurve", fHUDRadius, -60.0f, -15.0f,
            //    bgMaterial, primMaterial,
            //    () => {
            //        return new PolyCurveSO().Create(cockpit.ActiveScene.DefaultSOMaterial);
            //    });
            //AddChild(addCurveButton);


            /*
             *          HUDButton addBunnyButton = HUDBuilder.CreateGeometryIconClickButton(
             *              new HUDShape(HUDShapeType.Disc, fButtonRadius ),
             *              fHUDRadius, -45.0f, -30.0f, bgColor,
             *              new meshIconGenerator() { MeshPath = "icon_meshes/bunny_1k", UseMaterial = primMaterial, UseSize = fButtonRadius * 0.7f });
             *          addBunnyButton.Name = "addBunnyButton";
             *          addBunnyButton.OnClicked += (s, e) => {
             *              // TODO add existing mesh to scene
             *              cockpit.Parent.Scene.AddBox();
             *          };
             *          cockpit.AddUIElement(addBunnyButton, true);
             */



            // initialize selected-primitive indicator icon
            fMesh     iconMesh     = null;
            fMaterial iconMaterial = null;

            try {
                iconMesh     = new fMesh(Resources.Load <Mesh>("tool_icons/star"));
                iconMaterial = MaterialUtil.CreateStandardVertexColorMaterialF(Color.white);
            } catch { }
            if (iconMesh == null)
            {
                iconMesh     = new fMesh(UnityUtil.GetPrimitiveMesh(PrimitiveType.Sphere));
                iconMaterial = MaterialUtil.CreateStandardMaterialF(Color.yellow);
            }
            indicatorGO = new fMeshGameObject(iconMesh);
            indicatorGO.SetName("active_star");
            indicatorGO.SetMesh(iconMesh);
            indicatorGO.SetMaterial(iconMaterial);
            indicatorGO.SetLocalScale(fIndicatorSize * Vector3f.One);
            indicatorGO.SetLocalPosition(indicatorGO.GetLocalPosition() +
                                         fIndicatorShift * (Vector3f.AxisY - 1 * Vector3f.AxisZ + Vector3f.AxisX));

            indicatorButton = buttons[0];   // this is default material
            indicatorButton.AppendNewGO(indicatorGO, indicatorButton.RootGameObject, false);
        }