Bounding Box intersection - revit-api

Question

To find elements that are intersecting a geometry I am using the example post by Jeremy in his blog http://thebuildingcoder.typepad.com/blog/2010/12/find-intersecting-elements.html. But the bounding box is always paralell to the axis X, Y and Z and this may cause a problem, like return elements that are not really clashing, because sometimes the bounding box it's not always coincident with the geometry because the family instance is rotated. Besides that, there is the problem that the bounding box will consider the geometry of the symbol and not the instance, and will consider the flipped geometry too, it means that the bounding box is bigger than I am looking for. Is there a way to get the real geometry that are in the currently view ? How can I solve this problem ?

Answer 1

There are many way to address this. Generally, when performing clash detection, you will always run a super fast pre-processing step first to determine candidate elements, and then narrow down the search step by step more precisely in following steps. In this case, you can consider the bounding box intersection the first step, and then perform post-processing afterwards to narrow down the result to your exact goal.
One important question is: does the bounding box really give you all the elements you need, plus more? Are you sure there are none missing?
Once that is settled, all you need to do is add post-processing steps applying the detailed considerations that you care about.
A simple one might be: are all the target element geometry vertices contained in the target volume?
A more complex one might involve retrieving the full solid of the target element and the target volume and performing a Boolean intersection between them to determine completely and exactly whether they intersect, are disjunct, or contained in each other.
Many others are conceivable.

Answer 2

I am using another strategy that is acess the geometry of the instance to verify if the face of the family instace are clashing with a closer conduit.
class FindIntersection
{
public Conduit ConduitRun { get; set; }
public FamilyInstance Jbox { get; set; }
public List<Conduit> GetListOfConduits = new List<Conduit>();
public FindIntersection(FamilyInstance jbox, UIDocument uiDoc)
{
XYZ jboxPoint = (jbox.Location as LocationPoint).Point;
FilteredElementCollector filteredCloserConduits = new FilteredElementCollector(uiDoc.Document);
List<Element> listOfCloserConduit = filteredCloserConduits.OfClass(typeof(Conduit)).ToList().Where(x =>
((x as Conduit).Location as LocationCurve).Curve.GetEndPoint(0).DistanceTo(jboxPoint) < 30 ||
((x as Conduit).Location as LocationCurve).Curve.GetEndPoint(1).DistanceTo(jboxPoint) < 30).ToList();
//getting the location of the box and all conduit around.
Options opt = new Options();
opt.View = uiDoc.ActiveView;
GeometryElement geoEle = jbox.get_Geometry(opt);
//getting the geometry of the element to acess the geometry of the instance.
foreach (GeometryObject geomObje1 in geoEle)
{
GeometryElement geoInstance = (geomObje1 as GeometryInstance).GetInstanceGeometry();
//the geometry of the family instance can be acess by this method that returns a GeometryElement type.
//so we must get the GeometryObject again to acess the Face of the family instance.
if (geoInstance != null)
{
foreach (GeometryObject geomObje2 in geoInstance)
{
Solid geoSolid = geomObje2 as Solid;
if (geoSolid != null)
{
foreach (Face face in geoSolid.Faces)
{
foreach (Element cond in listOfCloserConduit)
{
Conduit con = cond as Conduit;
Curve conCurve = (con.Location as LocationCurve).Curve;
SetComparisonResult set = face.Intersect(conCurve);
if (set.ToString() == "Overlap")
{
//getting the conduit the intersect the box.
GetListOfConduits.Add(con);
}
}
}
}
}
}
}
}
}

Answer 3

Can you please provide a complete minimal reproducible case so we can understand the exact context and analyse what can be done? Maybe you could include one axis-aligned junction box and one that is not, so we can see how ell versus how badly your existing algorithm performs. Thank you!

Answer 4

I summarised this discussion and the results to date in a blog post on filtering for intersecting elements and conduits intersecting a junction box.