Is the first Edgeloop still the outer loop?
The area approach mentioned in the above link is probably more reliable but I had an alternate idea based on getting all co-ordinates linked to the edge loops they are from and then finding the minimums in a certain direction. Below I've taken min.x but but same would apply for min.y, max.x and max.y
I could not think of a situation where if you convert the 3D co-ordinates of each edge curve to a co-ordinate system of the plane you would end up with a min.x for the outer loop greater than the min.x for the inner loop. Similarly the max.x of the outer loop should be greater than the max.x of the inner loop. This appeared to be true for most cases but then there was the issue of circular curves where the two end points could be further back than a point projecting into the centre of the curve. So I decided to treat cyclic curves differently by checking for min.x along the curve.
I came up with the two below functions one for planner faces and the other for faces in general. They both seem to give reliable results on the cases in the image below (based on expected edge counts for the outer loops). However there may be a case that fail. The parts related to co-ordinate transformations may need looking at (there may be better approaches). I checked the z of each transformed point to see that it was 0 or virtually 0, so seems to be as expected.
For the more generalised method I'm using API functionality which projects a point onto a face, I was expecting some possible intersection errors since I'm checking points on the boundary of the face. I've not checked such things in detail.
In summary the area method mentioned in link is likely better and more reliable, not sure which is faster.
Public Shared Function Run(ByVal commandData As Autodesk.Revit.UI.ExternalCommandData) As Autodesk.Revit.UI.Result
Dim IntApp As UIApplication = commandData.Application
Dim IntUIDoc As UIDocument = IntApp.ActiveUIDocument
If IntUIDoc Is Nothing Then Return Result.Failed Else
Dim IntDoc As Document = IntUIDoc.Document
Dim R As Reference = Nothing
Try
R = IntUIDoc.Selection.PickObject(Selection.ObjectType.Face)
Catch ex As Exception
End Try
If R Is Nothing Then Return Result.Cancelled Else
Dim F_El As Element = IntDoc.GetElement(R.ElementId)
If F_El Is Nothing Then Return Result.Failed Else
Dim F As Face = TryCast(F_El.GetGeometryObjectFromReference(R), Face)
If F Is Nothing Then Return Result.Failed Else
Dim EA1 As EdgeArray = PlannerFaceOuterLoop(F)
Dim EA2 As EdgeArray = OuterLoop(F)
Return Result.Succeeded
End Function
Public Shared Function OuterLoop(F As Face) As EdgeArray
Dim MinU = Function(C As Curve) As Double
If C.IsCyclic Then
Dim Min As Double = Double.NaN
For I = 0 To 20
Dim Param As Double = I / 20
Dim CuvPt As XYZ = C.Evaluate(Param, True)
Dim IR As IntersectionResult = F.Project(CuvPt)
If IR Is Nothing = False Then
If Min = Double.NaN Then
Min = IR.UVPoint.U
Else
If IR.UVPoint.U < Min Then
Min = IR.UVPoint.U
End If
End If
End If
Next
Return Min
Else
Dim Pt1 As XYZ = C.GetEndPoint(0)
Dim Pt2 As XYZ = C.GetEndPoint(1)
Dim IR1 As IntersectionResult = F.Project(Pt1)
Dim IR2 As IntersectionResult = F.Project(Pt2)
If IR1 Is Nothing OrElse IR2 Is Nothing Then Return Double.NaN
If IR1.UVPoint.U < IR2.UVPoint.U Then
Return IR1.UVPoint.U
Else
Return IR2.UVPoint.U
End If
End If
End Function
Dim Loops As IEnumerable(Of EdgeArray)
Loops = From L As EdgeArray In F.EdgeLoops
Select L
Dim Cv As IEnumerable(Of Tuple(Of EdgeArray, Double))
Cv = From L2 As EdgeArray In Loops
From L3 As Edge In L2
Let Mu As Double = MinU(L3.AsCurve)
Where Mu <> Double.NaN
Select New Tuple(Of EdgeArray, Double)(L2, Mu)
Dim Out As Tuple(Of EdgeArray, Double) = Cv.ToList.Find(Function(Jx) Jx.Item2 = Cv.Min(Function(Jv) Jv.Item2))
If Out Is Nothing Then
Return Nothing
Else
Return Out.Item1
End If
End Function
Public Shared Function PlannerFaceOuterLoop(F As Face) As EdgeArray
Dim PF As PlanarFace = TryCast(F, PlanarFace)
If PF Is Nothing Then Return Nothing Else
Dim FN As XYZ = PF.FaceNormal
Dim T As Transform = Transform.Identity
T.BasisZ = FN
T.BasisX = PF.XVector
T.BasisY = PF.YVector
T.Origin = PF.Origin
'Dim Zeds As New List(Of Double)
Dim MinU = Function(C As Curve) As Double
If C.IsCyclic Then
Dim Min As Double = Nothing
For I = 0 To 20
Dim Param As Double = I / 20
Dim CuvPt As XYZ = C.Evaluate(Param, True)
Dim XYZt As XYZ = T.Inverse.OfPoint(CuvPt)
If I = 0 Then
Min = XYZt.X
Else
If XYZt.X < Min Then
Min = XYZt.X
End If
End If
Next
Return Min
Else
Dim Pt1 As XYZ = C.GetEndPoint(0)
Dim Pt2 As XYZ = C.GetEndPoint(1)
Dim XYZp As XYZ() = New XYZ(1) {}
XYZp(0) = T.Inverse.OfPoint(Pt1)
XYZp(1) = T.Inverse.OfPoint(Pt2)
' Zeds.Add(XYZp(0).Z)
' Zeds.Add(XYZp(1).Z)
If XYZp(0).X < XYZp(1).X Then
Return XYZp(0).X
Else
Return XYZp(1).X
End If
End If
End Function
Dim Loops As IEnumerable(Of EdgeArray)
Loops = From L As EdgeArray In F.EdgeLoops
Select L
Dim Cv As IEnumerable(Of Tuple(Of EdgeArray, Double))
Cv = From L2 As EdgeArray In Loops
From L3 As Edge In L2
Let Mu As Double = MinU(L3.AsCurve)
Select New Tuple(Of EdgeArray, Double)(L2, Mu)
Dim Out As Tuple(Of EdgeArray, Double) = Cv.ToList.Find(Function(Jx) Jx.Item2 = Cv.Min(Function(Jv) Jv.Item2))
If Out Is Nothing Then
Return Nothing
Else
Return Out.Item1
End If
End Function
Dear Rpthomas108,
Thank you very much for sharing this nice idea and implementation!
It makes sense to me. Serious testing will be in order 🙂
I hope Philippe found it useful. How sad that he does not say.
I have a couple of suggestions:
- When you say 'planner' face, you presumably mean 'planar'.
- Why just handle cyclic curves the way you do? Don't arcs deserver the same treatment, even if they are not cyclic? And other non-linear curves?
- Instead of using `C.Evaluate` twenty times over, you could call the curve Tessellate method. That would do it for you. It also handles the case of a linear curve gracefully, returning just the two end points, so your MinU function could be shortened and simplified.
Cheers,
Jeremy
I found your code really hard to understand, so I refactored it and rewrote some parts like this:
<Transaction(TransactionMode.ReadOnly)>
Public Class AdskCommand
Implements IExternalCommand
Shared Function MinU1(C As Curve, F As Face) As Double
If C.IsCyclic Then
Dim Min As Double = Double.NaN
For I = 0 To 20
Dim Param As Double = I / 20
Dim CuvPt As XYZ = C.Evaluate(Param, True)
Dim IR As IntersectionResult = F.Project(CuvPt)
If IR Is Nothing = False Then
If Min = Double.NaN Then
Min = IR.UVPoint.U
Else
If IR.UVPoint.U < Min Then
Min = IR.UVPoint.U
End If
End If
End If
Next
Return Min
Else
Dim Pt1 As XYZ = C.GetEndPoint(0)
Dim Pt2 As XYZ = C.GetEndPoint(1)
Dim IR1 As IntersectionResult = F.Project(Pt1)
Dim IR2 As IntersectionResult = F.Project(Pt2)
If IR1 Is Nothing OrElse IR2 Is Nothing Then Return Double.NaN
If IR1.UVPoint.U < IR2.UVPoint.U Then
Return IR1.UVPoint.U
Else
Return IR2.UVPoint.U
End If
End If
End Function
Public Shared Function OuterLoop(F As Face) As EdgeArray
Dim Loops As EdgeArrayArray = F.EdgeLoops
Dim Cv As List(Of Tuple(Of EdgeArray, Double)) =
New List(Of Tuple(Of EdgeArray, Double))(Loops.Size)
For Each L2 As EdgeArray In Loops
For Each L3 As Edge In L2
Dim Mu As Double = MinU1(L3.AsCurve, F)
Cv.Add(New Tuple(Of EdgeArray, Double)(L2, Mu))
Next
Next
Dim Out As Tuple(Of EdgeArray, Double) =
Cv.Find(Function(Jx) Jx.Item2 = Cv.Min(Function(Jv) Jv.Item2))
If Out Is Nothing Then
Return Nothing
Else
Return Out.Item1
End If
End Function
Shared Function MinU2(C As Curve, T As Transform) As Double
If C.IsCyclic Then
Dim Min As Double = Nothing
For I = 0 To 20
Dim Param As Double = I / 20
Dim CuvPt As XYZ = C.Evaluate(Param, True)
Dim XYZt As XYZ = T.Inverse.OfPoint(CuvPt)
If I = 0 Then
Min = XYZt.X
Else
If XYZt.X < Min Then
Min = XYZt.X
End If
End If
Next
Return Min
Else
Dim Pt1 As XYZ = C.GetEndPoint(0)
Dim Pt2 As XYZ = C.GetEndPoint(1)
Dim XYZp As XYZ() = New XYZ(1) {}
XYZp(0) = T.Inverse.OfPoint(Pt1)
XYZp(1) = T.Inverse.OfPoint(Pt2)
' Zeds.Add(XYZp(0).Z)
' Zeds.Add(XYZp(1).Z)
If XYZp(0).X < XYZp(1).X Then
Return XYZp(0).X
Else
Return XYZp(1).X
End If
End If
End Function
Public Shared Function PlanarFaceOuterLoop(F As Face) As EdgeArray
Dim PF As PlanarFace = TryCast(F, PlanarFace)
If PF Is Nothing Then Return Nothing Else
Dim FN As XYZ = PF.FaceNormal
Dim T As Transform = Transform.Identity
T.BasisZ = FN
T.BasisX = PF.XVector
T.BasisY = PF.YVector
T.Origin = PF.Origin
'Dim Zeds As New List(Of Double)
Dim Loops As EdgeArrayArray = F.EdgeLoops
Dim Cv As List(Of Tuple(Of EdgeArray, Double)) =
New List(Of Tuple(Of EdgeArray, Double))(Loops.Size)
For Each L2 As EdgeArray In Loops
For Each L3 As Edge In L2
Dim Mu As Double = MinU2(L3.AsCurve, T)
Cv.Add(New Tuple(Of EdgeArray, Double)(L2, Mu))
Next
Next
Dim Out As Tuple(Of EdgeArray, Double) =
Cv.ToList.Find(Function(Jx) Jx.Item2 = Cv.Min(Function(Jv) Jv.Item2))
If Out Is Nothing Then
Return Nothing
Else
Return Out.Item1
End If
End Function
Public Function Execute(
ByVal commandData As ExternalCommandData,
ByRef message As String,
ByVal elements As ElementSet) _
As Result Implements IExternalCommand.Execute
Dim uiapp As UIApplication = commandData.Application
Dim uidoc As UIDocument = uiapp.ActiveUIDocument
Dim app As Application = uiapp.Application
Dim doc As Document = uidoc.Document
Dim sel As Selection = uidoc.Selection
Dim R As Reference = Nothing
Try
R = sel.PickObject(ObjectType.Face)
Catch ex As Exception
End Try
If R Is Nothing Then Return Result.Cancelled Else
Dim F_El As Element = doc.GetElement(R.ElementId)
If F_El Is Nothing Then Return Result.Failed Else
Dim F As Face = TryCast(F_El.GetGeometryObjectFromReference(R), Face)
If F Is Nothing Then Return Result.Failed Else
Dim EA1 As EdgeArray = PlanarFaceOuterLoop(F)
Dim EA2 As EdgeArray = OuterLoop(F)
Return Result.Succeeded
End Function
End Class
Here are your methods simplified and rewritten in C#:
#region Rpthomas108 searches for minimum point
// In Revit API discussion forum thread
// https://forums.autodesk.com/t5/revit-api-forum/is-the-first-edgeloop-still-the-outer-loop/m-p/7225379
public static double MinU( Curve C, Face F )
{
return C.Tessellate()
.Select<XYZ, IntersectionResult>( p => F.Project( p ) )
.Min<IntersectionResult>( ir => ir.UVPoint.U );
}
public static double MinX( Curve C, Transform Tinv )
{
return C.Tessellate()
.Select<XYZ, XYZ>( p => Tinv.OfPoint( p ) )
.Min<XYZ>( p => p.X );
}
public static EdgeArray OuterLoop( Face F )
{
EdgeArray eaMin = null;
EdgeArrayArray loops = F.EdgeLoops;
double uMin = double.MaxValue;
foreach( EdgeArray a in loops )
{
double uMin2 = double.MaxValue;
foreach( Edge e in a )
{
double min = MinU( e.AsCurve(), F );
if( min < uMin2 ) { uMin2 = min; }
}
if( uMin2 < uMin )
{
uMin = uMin2;
eaMin = a;
}
}
return eaMin;
}
public static EdgeArray PlanarFaceOuterLoop( Face F )
{
PlanarFace face = F as PlanarFace;
if( face == null )
{
return null;
}
Transform T = Transform.Identity;
T.BasisZ = face.FaceNormal;
T.BasisX = face.XVector;
T.BasisY = face.YVector;
T.Origin = face.Origin;
Transform Tinv = T.Inverse;
EdgeArray eaMin = null;
EdgeArrayArray loops = F.EdgeLoops;
double uMin = double.MaxValue;
foreach( EdgeArray a in loops )
{
double uMin2 = double.MaxValue;
foreach( Edge e in a )
{
double min = MinX( e.AsCurve(), Tinv );
if( min < uMin2 ) { uMin2 = min; }
}
if( uMin2 < uMin )
{
uMin = uMin2;
eaMin = a;
}
}
return eaMin;
}
#endregion // Rpthomas108 searches for minimum point
Note how short and sweet MinU and MinX became?
I added them to The Building Coder samples release:
https://github.com/jeremytammik/the_building_coder_samples/releases/tag/2018.0.134.3
Cheers,
Jeremy
Dear Richard,
Yes, I like your approach a lot.
Kiss! -- https://en.wikipedia.org/wiki/KISS_principle
Yes, Tessellate is very handy indeed.
I love lambda expressions too. I am just not fluent in VB, and never saw them there before 🙂
Cheers,
Jeremy
Thank you for the nice idea.
However, I am not immediately convinced...
Imagine a situation with many rooms, many of which have holes.
Imagine that many of the holes are the exact same size as many of the other rooms.
How do you tell them apart, if all you consider is their area?
Search the Revit API DLLs for something named IFC. I think the namespace is
using Autodesk.Revit.DB.IFC;
Dear Richard,
Congratulations on finding this egg, and best of luck discovering all the others!
Yes, another developer who is a big fan of the hidden wonders of the Rev it API utility classes is Rudolf Honke:
https://thebuildingcoder.typepad.com/blog/2013/04/handy-utility-classes.html
Cheers,
Jeremy
I tried using SortCurveLoops on the the face shown below, expecting to get one list with the outer loop and one list with the 3 inner loops, but I got one list containing one list containing two loops.
This article also mentions co-planar loops in the description of ValidateCurveLoops. Perhaps the problem I had is caused by the fact that also SortCurveLoops only works with co-planar loops?
Here is the code I use to find the outer loop and all the inner loops. It finds the outer loop by cycling through all the tessellated points of all the loop edges and finding the one with the lowest U.
I did a few tests and it seems to work well. I am surprised to see that my short function does the same job as other long functions shown in the previous posts. I am learning LINQ, so I spent some time to get this to work with LINQ, but my previous version using 3 nested foreach was very simple to do.
Am I doing something wrong?
Am I doing something different from what this post describes?
public Face Face;
private CurveLoop _outerLoop;
private List<CurveLoop> _innerLoops;
private void GetInnerAndOuterLoops()
{
var allLoops = Face.GetEdgesAsCurveLoops();
_outerLoop = allLoops
.SelectMany(loop => loop
.SelectMany(curve => curve.Tessellate()
.Select(point => (Face.Project(point).UVPoint.V, Loop: loop))))
.Aggregate((lowestLoop, nextLoop) => lowestLoop.V < nextLoop.V ? lowestLoop : nextLoop).Loop;
_innerLoops = allLoops.Where(loop => loop != _outerLoop).ToList();
}
If it works it works.
One thing I considered at the time was resolution of the points you get from tessellate i.e. if you have a curve does one of the points on that curve (from tessellate) describe the actual minimum location of that curve (for some curves that is unlikely to be the case). Since there is the parametric curve and the actual points are obtained from that. Below is an exaggerated example of what I mean by that. Depends also on rotation of UV axis on face in comparison to those points.
For the most part I don't think such a thing would cause issues unless you set out to prove it didn't work i.e. in a real world scenario there is no arrangement you would likely have that would be affected by such things. So it's a question of comfort level through testing really.
I think it has also since been noted that there are patterns in how the faces are constructed that gives away the actual outer loop of a face.
Was also at the time dealing with PlanarFaces only so also should note that for those you can use Face.IsInside with solid creation utils, this makes things far more straightforward than my original above code and perhaps more reliable i.e. extrude each loop and check points from each within faces of one another to find other loop.
You say you got one list with one list with two loops...
If you are unsure which loop is which, or, in any case, I would highly recommend implementing some little debugging utility functions to display those loops graphically, or it will be very hard to understand what you are getting.
I implemented such stuff in several blog posts using the Creator class:
- Slab Boundary
- Model Line Creation
- Slab Side Faces
- Wall Compound Layers
- Wall Elevation Profile
- Curtain Wall Geometry
- Model Curve Creator
- Iteration and Springtime – Change is the Only Constant
- Top Faces of Sloped Wall
- Retrieving Detailed Wall Layer Geometry
- Slab Boundary Revisited
- Generating a MidCurve Between Two Curve Elements
- AU Day 1, Revit 2014 API Class and Bounding Box Rotation
- Calculating a Rolling Offset Between Two Pipes
- Creating a Sloped Wall
- Curved Wall Elevation Profile and Creator Class Update
- Index, Debug, Curves, Distance, Deleting PrintSetup
Developer Advocacy and Support + The Building Coder + Autodesk Developer Network + ADN Open
Thank you for the list of articles, it will be very helpful in the near future!
This article seems to mention the same problem that I found in SortCurveLoops.
I did another test with SortCurveLoops, and indeed it seems to be working reliably only with planar faces. With curved faces it usually does nothing. Only in one curved face I was able to get 2 out of the 4 loops, but it usually gets none.
In this snapshot you can see two masses. The first one has only planar faces, the second one is a copy of the first one with a void that creates a curved face.
The texts show the first line of each loop with the loop indexes as returned by SortCurveLoops. I like to create texts at 1/3 of each line, so it visually gives an idea of the direction of the loop. Just looking at the texts you immediately understand which loops are clockwise and which ones are counterclockwise.
I have the feeling that SortCurveLoops projects the curves to a plane, then crunches the numbers on the projected curves. If this is the case, then it will never be reliable on curved faces. The correct approach would be to work on the UV coordinates.
Here is the code I used:
var loops = face.GetEdgesAsCurveLoops();
var sortedLoops = ExporterIFCUtils.SortCurveLoops(loops);
for (var i = 0; i < sortedLoops.Count; i++)
{
for (var j = 0; j < sortedLoops[i].Count; j++)
{
CreateTextNote($"[{i}][{j}]", sortedLoops[i][j].First().Evaluate(0.33, true), doc);
}
}
TextNote CreateTextNote(string text, XYZ origin, Document doc)
{
var options = new TextNoteOptions
{
HorizontalAlignment = HorizontalTextAlignment.Center,
VerticalAlignment = VerticalTextAlignment.Middle,
TypeId = doc.GetDefaultElementTypeId(ElementTypeGroup.TextNoteType)
};
return TextNote.Create(doc, doc.ActiveView.Id, origin, text, options);
}