Obj files import and cursor position in HelixToolkit.SharpDX

Question

I am new in HelixToolkit.SharpDX and I have 2 questions, maybe anyone can help me:

First: I want to import obj model (with textures) and display it in Viewport3DX. How to do it correctly? Now I have next:

ObjReader Reader = new HelixToolkit.Wpf.SharpDX.ObjReader();
List<Object3D> objs = Reader.Read(ModelPath);

After reading objs variable contains near 1000 objects. What shall be the next steps to to display model in viewport?

Second: And one more question: How to receive cursor position in Viewport3DX. Is there some property like CursorPosition in HelixViewport3D?

Thank you in advance!

Answer 1

First

As you have your List<Object3D> objs you could create a Element3DCollection and bind to it within your xaml code.

XAML Code (put this snippet into your Viewport3DX)

Create a GroupModel3D and add bindings its properties

<hx:GroupModel3D 
    x:Name="Viewport3D"
    ItemsSource="{Binding YourElement3DCollection}"   
    Transform="{Binding YourTransformToMousePosition}"/>

---

Somewhere in your ViewModel

Fill your Element3DCollection with Object3Ds

ObjReader Reader = new HelixToolkit.Wpf.SharpDX.ObjReader();
List<Object3D> objs = Reader.Read(ModelPath);

var ele3DCollection = new Element3DCollection();
foreach (var ob in objs)
{
    var meshGeometry = new MeshGeometryModel3D
    {
        Geometry = ob.Geometry,
        Material = ob.Material,
    };
    ele3DCollection.Add(meshGeometry);

    // Run this line if you are using a render host
    meshGeometry.Attach(Viewport3D.RenderHost);
}

// Now assign the ele3DCollection to the property you bound to and raise property changed
YourElement3DCollection = ele3DCollection;

where YourElement3DCollection is of type Element3DCollection. Don't forget to raise INotifyPropertyChanged.

Alternatively you could bind to a DependencyProperty of your code behind. Then just call InvalidateProperty(YourElement3DCollectionProperty) after assigning it.

---

Second

You could perform a raycast from your mouse position to a object in the scene (maybe an XY-Plane intersecting the origin). Then use the coordinates of this point and create your Transform3D object.

Untested code (code behind):

var yourRay = Viewport3D.UnProjectToRay(Mouse.GetPosition(Viewport3D));

var yourTargetPoint = yourRay.PlaneIntersection(new Point3D(0, 0, 0), new Vector3D(0, 0, 1));

// todo: check for null
var yourTranslation = new TranslateTransform3D(
    yourTargetPoint.Value.X, yourTargetPoint.Value.Y, yourTargetPoint.Value.Z);

// assign the relation to your viewModel somehow
((YourViewModelType)DataContext).YourTransformToMousePosition = yourTranslation;

where YourTransformToMousePosition is of type Transform3D