如何在螺旋工具箱sharpDX视图中选择最顶层的元素

Question

我正在为我大学的一个项目(HelixToolKit library)使用helix-toolkit库的sharpDX分支

目前我正在寻找一种方法来正确选择元素在一个viewport。

我在helixtoolkit库的源代码中找到了一个有用的示例:GitHub上的示例代码

public class MyLineGeometryModel3D : LineGeometryModel3D
{
    private Color? initialColor = null;
    public override bool HitTest(Ray rayWS, ref List<HitTestResult> hits)
    {
        if (initialColor == null)
        {
            initialColor = this.Color;
        }
        var result = base.HitTest(rayWS, ref hits);
        var pressedMouseButtons = Viewport3DX.GetPressedMouseButtons();
        if (pressedMouseButtons == 0 || pressedMouseButtons.HasFlag(MouseButtons.Left))
        {
            this.Color = result ? Color.Red : this.initialColor.Value;
        }
        return result;
    }

}

我设法让它在我的应用程序中运行。然而，不是只选择最上面的元素，而是选择所有与射线相交的元素。可能需要某种处理程序函数来突出显示距离最短的元素?

我检查了一些标准的WPF解决方案，他们经常使用事件处理程序。(例如在WPF中进行3D命中测试)

private void m_viewport3d_MouseDown(object sender, MouseButtonEventArgs e)
{
    Point mousePos = e.GetPosition(m_viewport3d);
    PointHitTestParameters hitParams = new PointHitTestParameters(mousePos);
    HitTestResult result = VisualTreeHelper.HitTest(m_viewport3d, mousePos);
    RayMeshGeometry3DHitTestResult rayMeshResult = result as RayMeshGeometry3DHitTestResult;
    if (rayMeshResult != null)
    {
        MeshGeometry3D mesh = new MeshGeometry3D();
        mesh.Positions.Add(rayMeshResult.MeshHit.Positions[rayMeshResult.VertexIndex1]);
        mesh.Positions.Add(rayMeshResult.MeshHit.Positions[rayMeshResult.VertexIndex2]);
        mesh.Positions.Add(rayMeshResult.MeshHit.Positions[rayMeshResult.VertexIndex3]);
        mesh.TriangleIndices.Add(0);
        mesh.TriangleIndices.Add(1);
        mesh.TriangleIndices.Add(2);
        GeometryModel3D marker = new GeometryModel3D(mesh, new DiffuseMaterial(Brushes.Blue));
        //...add marker to the scene...
    }
}

使用事件处理程序是一个明智的解决方案吗?如果是，如何在eventandler中获得用于调用HitTest函数的射线元素?

Answer 1

使用Viewport方法FindNearest:

private void OnMouseDown(object sender, MouseButtonEventArgs e)
{     
    Viewport3DX vp = e.Source as Viewport3DX;
    Point3D p;
    Vector3D v;
    Model3D m;
    if (vp.FindNearest(e.GetPosition(vp), out p, out v, out m))
    {
         //Do something with the found object
    }
 }

Answer 2

所以，我实际上找到了一个解决方案，这可能不是完美的。但也许这对某些人有用。

        private void ViewPort3D_OnMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {
            Ray ray = this.ViewPort3D.UnProject(new Vector2((float)e.GetPosition(ViewPort3D).X, (float)e.GetPosition(ViewPort3D).Y));
            var hits = new List<HitTestResult>();
            // dictionary for connecting the id of the specific element and its distance
            var hitElements = new Dictionary<int, double>();
            // loop over all MeshGeometryModel3D elements
            foreach (var geometry in Geometrys)
            {
                var isHit = geometry.Model3D.HitTest(ray, ref hits);
                if (isHit)
                {
                    hitElements.Add(geometry.Id, hits[hits.Count - 1].Distance);
                }
            }
            if (hits.Count > 0)
            {
                double minDistance = hitElements.First().Value;
                int id_of_hit_element = hitElements.First().Key;
                foreach (var hit in hitElements)
                {
                    if (hit.Value < minDistance)
                    {
                        minDistance = hit.Value;
                        id_of_hit_element = hit.Key;
                    }
                }
                var topElement = Geometrys.Find(geometry => geometry.Id == id_of_hit_element);
                // do something with top element
            }
        }

注:顺便说一句，不是计算机科学家，只是一个土木工程专业的学生，尽他最大的努力xD