EventManager3D Class

Some mouse events support is already available with WPF's ModelUIElement3D class, but it only support some of the mouse events and provide only limited information about the hit objects. Its usage also requires breaking the 3D objects that are grouped with Model3DGroup into individual ModelUIElement3D objects. Using EventManager3D provides much better events support and does not require any change in the 3D objects organization.

The following mouse events are supported:
MouseEnter
MouseLeave,
MouseMove,
MouseDown,
MouseUp,
MouseClick,
MouseDoubleClick,
MouseWheel,
BeginMouseDrag,
MouseDrag,
EndMouseDrag.

When a .Net 4 version of Ab3d.PowerToys library is used, EventManager3D also supports the following touch events:
TouchEnter,
TouchDown,
TouchMove,
TouchUp,
TouchLeave.

It is also possible to use touch manipulations events (pinch scale and rotate). To use manipulation events, first set IsManipulationEnabled to true (some mouse events will not happen after that) and than you can subscribe to the following events:
ManipulationStarted,
ManipulationDelta,
ManipulationCompleted.

This way you do not need to do the complicated 3D hit testing any more. You can simply subscribe to mouse events. This way you the code is much simpler and better organized.

It is also possible to exclude some Visual3D objects from hit testing with RegisterExcludedVisual3D(Visual3D) method. This means that when the ray from the mouse will hit the excluded Visual3D, it will not produce a hit test but will continue with checking if there are any objects behind. To remove the Visual3D form exclusion list, call the RemoveExcludedVisual3D(Visual3D) method (exclusion list is also cleared when called ResetEventSources3D method).

This can be very useful for example when we are drawing an object or 3D line at the position of mouse hit. Without an option to exclude the drawn object or 3d line, we would get many MouseEnter and MouseLeave events because mouse will sometimes hit the back object and sometimes the drawn object or 3D line.

Important:
It is highly recommended not to have more than one EventManager3D object per Viewport3D. Having multiple EventManager3D object can greatly reduce the performance because each time the Viewport3D camera is changed, each EventManager3D must perform a full 3D hit testing from the current mouse position. This operation is very CPU intensive and can affect performance when there are many 3D objects in the scene. When multiple EventManager3D object are defined, then the 3D hit testing is performed multiple times. Therefore it is recommended to have only one EventManager3D object per Viewport3D.

It is also recommended to remove registered event sources after they are not used any more. This can be done with RemoveEventSource3D(BaseEventSource3D) method.

UpdateHitObjects(MouseEventArgs) method can be called to manually update the 3D objects that are behind the current mouse position. This is useful when the camera is changed without moving the mouse. In this case the 3D objects behind the mouse position can change. If this happens the MouseEnter, MouseLeave and other event handlers will be called from the UpdateHitObjects method.

Usage:

To use EventManager3D create an instance of EventManager3D class and pass TargetViewport3D as constructor parameter.

Than if you need to subscribe events on Model3D create ModelEventSource3D and set its TargetModel3D to the Model3D. Now you can subscribe to the events on the created ModelEventSource3D. The last thing to do is to register the ModelEventSource3D to the EventManager3D with the RegisterEventSource3D(BaseEventSource3D) method on the EventManager3D.

If you need to subscribe to events on Visual3D use VisualEventSource3D instead of ModelEventSource3D.

It is also possible to subscribe the same events on more Model3D or Visual3D objects. In this case use MultiModelEventSource3D or MultiVisualEventSource3D.

If you have read 3D objects with Ab3d.Reader3ds or have the 3D objects already organized in a Dictionary with name object pairs, you can define the objects or visuals by their name. In this case the NamedObjects dictionary must be set on EventManager3D.

The following sample shows how to subscribe to click event on MyBoxVisual3D object and change the material on the object.

private bool _isSelected;
Ab3d.Utilities.EventManager3D _eventManager;

private void SubscribeEvents()
{
    Ab3d.Utilities.VisualEventSource3D eventSource3D;

    _eventManager = new Ab3d.Utilities.EventManager3D(MyViewport3D);

    eventSource3D = new Ab3d.Utilities.VisualEventSource3D();
    eventSource3D.TargetVisual3D = MyBoxVisual3D;
    eventSource3D.MouseClick += new Ab3d.Common.EventManager3D.MouseButton3DEventHandler(eventSource3D_MouseClick);

    _eventManager.RegisterEventSource3D(eventSource3D);
}

void eventSource3D_MouseClick(object sender, Ab3d.Common.EventManager3D.MouseButton3DEventArgs e)
{
    Material newMaterial;

    if (_isSelected)
        newMaterial = new DiffuseMaterial(Brushes.Blue);
    else
        newMaterial = new DiffuseMaterial(Brushes.Red);

    MyBoxVisual3D.Material = newMaterial;

    _isSelected = !_isSelected;
}

Reference