Revit API射线法读取空间中相交的元素

Revit API提供根据射线来寻找经过的元素。方法是固定模式，没什么好说。
关键代码：doc.FindReferencesWithContextByDirection(ptStart, (ptEnd - ptStart), view3d)

//射线法寻找穿过的对象
[TransactionAttribute(Autodesk.Revit.Attributes.TransactionMode.Manual)]
public class FindSupporting : IExternalCommand
{
    public Result Execute(ExternalCommandData commandData, ref string messages, ElementSet elements)
    {

        UIApplication app = commandData.Application;
        Document doc = app.ActiveUIDocument.Document;
        Transaction trans = new Transaction(doc, "ExComm");
        trans.Start();

        Selection sel = app.ActiveUIDocument.Selection;
        //Reference ref1 = sel.PickObject(ObjectType.Element, "Please pick a beam");
        //FamilyInstance beam = doc.GetElement(ref1) as FamilyInstance;
        Reference ref1 = sel.PickObject(ObjectType.Element, "Please pick a duct");
        Duct duct = doc.GetElement(ref1) as Duct;

        //Read the beam's location line
        //LocationCurve lc = beam.Location as LocationCurve;
        LocationCurve lc = duct.Location as LocationCurve;
        Curve curve = lc.Curve;
        //取得线端点的方法
        XYZ ptStart = curve.get_EndPoint(0);
        XYZ ptEnd = curve.get_EndPoint(1);

        //move the two point a little bit lower, so the ray can go through the wall
        XYZ offset = new XYZ(0, 0, 0.01);//向量偏移的方法，这里向下偏移。
        ptStart = ptStart - offset;
        ptEnd = ptEnd - offset;

        View3D view3d = null;
        view3d = doc.ActiveView as View3D;
        if (view3d == null)
        {
            TaskDialog.Show("3D view", "current view should be 3D view");
            return Result.Failed;
        }

        double beamLen = curve.Length;
        //终点-起点就是线的方向。这里是射线法的关键代码。必须在三维视图下。
        IList<ReferenceWithContext> references = doc.FindReferencesWithContextByDirection(ptStart, (ptEnd - ptStart), view3d);

        //ElementSet wallSet = app.Application.Create.NewElementSet();

        sel.Elements.Clear();
        double tolerate = 0.00001;
        foreach (ReferenceWithContext reference in references)
        {
            Reference ref2 = reference.GetReference();//取得引用
            ElementId id = ref2.ElementId;
            Element elem = doc.get_Element(id);

            if (elem is Wall)
            {
                if (reference.Proximity < (beamLen + tolerate))//Proximity接近，即与射线原点的距离。
                {
                    sel.Elements.Add(elem);
                }
            }
        }


        trans.Commit();

        return Result.Succeeded;
    }
}

url:http://greatverve.cnblogs.com/p/FindReferencesWithContextByDirection.html