Add ILPoints to ILPlotCube from user input (by mouse)

Question

I am new to ILNumerics, and I have a problem with some simple activity. I want to add Points to the Plot on user mouse input. User clicked for example point 5,4 on the plot, and this point have to draw on this position. I had some problems to transform location of a mouse to the plot coordinates, and I found the solution here, but it's not ideal for me. What I have done:

private void ilpGraph_Load(object sender, EventArgs e)
    {
        var scene = new ILScene();

        var plotCube = scene.Add(
            new ILPlotCube()
            {
                new PointsGroup()
            });

        plotCube.Limits.Set(new Vector3(0, 0, 0), new Vector3(10, 10, 0));

        plotCube.MouseClick += plotCube_MouseClick;

        ilpGraph.Scene = scene;
    }

void plotCube_MouseClick(object sender, ILMouseEventArgs e)
    {
        var pos = new Vector3(0, 0, 0);

        ILGroup plotcubeGroup = sender as ILGroup;
        ILGroup group = plotcubeGroup.Children.Where(item => item.Tag == "PointsGroup").First() as ILGroup;
        if (group != null)
        {
            // walk up to the next camera node 
            Matrix4 trans = group.Transform;
            while (!(group is ILCamera) && group != null)
            {
                group = group.Parent;
                // collect all nodes on the path up
                trans = group.Transform * trans;
            }
            if (group != null && (group is ILCamera))
            {
                // convert args.LocationF to world coords
                // The Z coord is not provided by the mouse! -> choose arbitrary value
                pos = new Vector3(e.LocationF.X * 2 - 1, e.LocationF.Y * -2 + 1, 0);
                // invert the matrix.
                trans = Matrix4.Invert(trans);
                // trans now converts from the world coord system (at the camera) to 
                // the local coord system in the 'target' group node (surface). 
                // In order to transform the mouse (viewport) position, we 
                // left multiply the transformation matrix.
                pos = trans * pos;
            }
        }

        // it's for testing now
        var pg = (sender as ILPlotCube).Plots.Children[0];
        var t = ((PointsGroup)pg).Points.Positions;
        int dc = t.DataCount;

        t.Update(dc, 1, new[] { pos.X, pos.Y, 0.0f });
        e.Refresh = true;
    }

public class PointsGroup : ILGroup
{
    private ILPoints _points;

    public PointsGroup()
        : base((object)"PointsGroup", new Vector3?(), 0.0, new Vector3?(), new Vector3?(), new RenderTarget?())
    {
    }

    internal PointsGroup(PointsGroup source) : base((ILGroup) source)
    {
    }

    public ILPoints Points
    {
        get
        {
            if (_points == null)
                return new ILPoints();
            return _points;
        }

        set { _points = value; }
    }

    protected override ILNode CreateSynchedCopy(ILNode source)
    {
        return (ILNode)new PointsGroup();
    }

    public override ILNode Copy()
    {
        return (ILNode)new PointsGroup(this);
    }

    public override ILNode Synchronize(ILNode copy, ILSyncParams syncParams)
    {
        return base.Synchronize(copy, syncParams);
    }
}

What is the problem: If I don't define PointsGroup class, I can't localize mouse coordinates on plot (ILPoints is not an ILGroup and I don't know how to do it differently). With the PointsGroup coordinates are calculated good, but the coordinates are not remembered and not shown on the plot. I know why it happens, but I really don't know how to fix this. How to extend my PointsGroup class to get my values remembered and show on plot or how to modify coordinates calculation to work on ILPoints objects? Can anyone help me? Please