Inventor’s Auto Balloon tool is useful for generating balloons, but it is primarily designed as an interactive feature. In practice, this means working through a dialog, adjusting settings, and repeating those steps for each view. I built a iLogic rule that focuses on a different approach: a fast, single‑click action that produces a clean, predictable result without any dialog or manual tuning.
This makes it practical, not only for day‑to‑day work, but also for automated processes. Since the built‑in Auto Balloon function is not exposed through the API, having a scriptable alternative becomes especially useful in those scenarios.
The generated layout follows the same general idea as the default tool, with a few small adjustments to keep balloons closer to their parts and to maintain a structured result.
The individual improvements are modest. The main benefit is usability: a reliable, one‑click workflow that fits naturally into both manual use and automation.
Using the rule
- Copy the code into an external iLogic rule.
- (Optional) Add a ribbon button or shortcut to run it.
- Autodesk’s guide: How to add a rule to the ribbon.
- ButtonConstructor
- Run the rule
- select a drawing view, and wait for placement to complete.
Notes: Drawings with a large number of drawing curves may take longer because the rule evaluates candidate edges to find a clean attachment point per part.
Public Class ThisRule
Private Property DistanceFromEdge As Double = 2
Private Property minimalDistanceBetweenBaloons As Double = 1.4
Private Enum Edge
Top
Bottom
Left
Right
End Enum
Sub Main()
Dim doc As DrawingDocument = ThisDoc.Document
Dim sheet As Sheet = doc.ActiveSheet
Dim view As DrawingView = ThisApplication.CommandManager.Pick(SelectionFilterEnum.kDrawingViewFilter, "Select a drawing view.")
Dim tagCurves = CollectClosestCurvePerFile(view)
PlaceBalloons(doc, sheet, view, tagCurves)
End Sub
Private Function CollectClosestCurvePerFile(view As DrawingView) As List(Of TagCurve)
Dim viewTop = view.Top
Dim viewBottom = view.Top - view.Height
Dim viewLeft = view.Left
Dim viewRight = view.Left + view.Width
Dim byFile As New Dictionary(Of String, TagCurve)
For Each curve As DrawingCurve In view.DrawingCurves.Cast(Of DrawingCurve)()
' This only works with edges
Try
If TypeOf curve.ModelGeometry IsNot EdgeProxy Then Continue For
Catch
Continue For
End Try
Dim tagCurve As New TagCurve(curve)
If tagCurve.Occ.OccurrencePath.Count > 2 Then Continue For
' Closed curves (circles, ellipses) have no midpoint — fall back to the center.
Dim midPoint As Point2d = curve.MidPoint
If midPoint Is Nothing Then midPoint = curve.CenterPoint
tagCurve.DistanceToNearestViewEdge = MinDistanceToViewEdge(midPoint, viewTop, viewBottom, viewLeft, viewRight)
Dim existing As tagCurve = Nothing
If Not byFile.TryGetValue(tagCurve.FileName, existing) OrElse tagCurve.DistanceToNearestViewEdge < existing.DistanceToNearestViewEdge Then
byFile(tagCurve.FileName) = tagCurve
End If
Next
Return byFile.Values.ToList()
End Function
Private Shared Function MinDistanceToViewEdge(midPoint As Point2d, top As Double, bottom As Double, left As Double, right As Double) As Double
Return Math.Min(
Math.Min(Math.Abs(top - midPoint.Y), Math.Abs(bottom - midPoint.Y)),
Math.Min(Math.Abs(left - midPoint.X), Math.Abs(right - midPoint.X))
)
End Function
Private Sub PlaceBalloons(doc As DrawingDocument, sheet As Sheet, view As DrawingView, tagCurves As List(Of TagCurve))
Dim transientGeom = ThisApplication.TransientGeometry
Dim balloonDiameter = doc.StylesManager.ActiveStandardStyle.ActiveObjectDefaults.BalloonStyle.BalloonDiameter
Dim viewTop = view.Top + DistanceFromEdge
Dim viewBottom = view.Top - view.Height - DistanceFromEdge
Dim viewLeft = view.Left - DistanceFromEdge
Dim viewRight = view.Left + view.Width + DistanceFromEdge
' Phase 1: assign each curve to its closest edge and compute the desired leader endpoint.
Dim placements As New List(Of Placement)
For Each tagCurve As TagCurve In tagCurves
' Closed curves (circles, ellipses) have no midpoint — fall back to the center.
Dim midPoint As Point2d = TagCurve.Curve.MidPoint
If midPoint Is Nothing Then midPoint = TagCurve.Curve.CenterPoint
Dim chosenEdge = ChooseClosestEdge(midPoint, viewTop, viewBottom, viewLeft, viewRight)
Dim leader = ComputeLeaderPoint(chosenEdge, midPoint, viewTop, viewBottom, viewLeft, viewRight, balloonDiameter)
placements.Add(New Placement With {
.TagCurve = TagCurve,
.MidPoint = midPoint,
.ChosenEdge = chosenEdge,
.LeaderX = leader.X,
.LeaderY = leader.Y
})
Next
' Phase 2: per edge, sort by position along that edge, sweep forward to
' enforce minimum spacing, then center each tight cluster so the cluster's
' centroid matches the centroid of its desired positions. Order along the
' edge is preserved either way, so leaders still don't cross.
For Each edgeGroup In placements.GroupBy(Function(p) p.ChosenEdge)
Dim isHorizontal = (edgeGroup.Key = Edge.Top OrElse edgeGroup.Key = Edge.Bottom)
Dim ordered = If(isHorizontal,
edgeGroup.OrderBy(Function(p) p.LeaderX).ToList(),
edgeGroup.OrderBy(Function(p) p.LeaderY).ToList())
Dim desired(ordered.Count - 1) As Double
For i = 0 To ordered.Count - 1
desired(i) = If(isHorizontal, ordered(i).LeaderX, ordered(i).LeaderY)
Next
Dim actual(ordered.Count - 1) As Double
Dim lastPlaced As Double = Double.MinValue
For i = 0 To ordered.Count - 1
actual(i) = Math.Max(desired(i), lastPlaced + minimalDistanceBetweenBaloons)
lastPlaced = actual(i)
Next
' Walk forward and close out each cluster (consecutive balloons in tight
' contact) by shifting it back so sum(actual) = sum(desired) within the
' cluster.
Dim clusterStart = 0
For i = 1 To ordered.Count
If i = ordered.Count OrElse actual(i) - actual(i - 1) > minimalDistanceBetweenBaloons + 0.001 Then
Dim sumActual As Double = 0
Dim sumDesired As Double = 0
For j = clusterStart To i - 1
sumActual += actual(j)
sumDesired += desired(j)
Next
Dim shift = (sumActual - sumDesired) / (i - clusterStart)
For j = clusterStart To i - 1
actual(j) -= shift
Next
clusterStart = i
End If
Next
For i = 0 To ordered.Count - 1
If isHorizontal Then
ordered(i).LeaderX = actual(i)
Else
ordered(i).LeaderY = actual(i)
End If
Next
Next
' Phase 3: create balloons at the final positions.
For Each p In placements
Dim leaderPoints = ThisApplication.TransientObjects.CreateObjectCollection()
leaderPoints.Add(transientGeom.CreatePoint2d(p.LeaderX, p.LeaderY))
leaderPoints.Add(sheet.CreateGeometryIntent(p.TagCurve.Curve, p.MidPoint))
sheet.Balloons.Add(leaderPoints)
Next
End Sub
Private Shared Function ChooseClosestEdge(midPoint As Point2d, top As Double, bottom As Double, left As Double, right As Double) As Edge
Dim distTop = Math.Abs(top - midPoint.Y)
Dim distBottom = Math.Abs(bottom - midPoint.Y)
Dim distLeft = Math.Abs(left - midPoint.X)
Dim distRight = Math.Abs(right - midPoint.X)
Dim horizontalEdge As Edge = If(distTop <= distBottom, Edge.Top, Edge.Bottom)
Dim horizontalDist = Math.Min(distTop, distBottom)
Dim verticalEdge As Edge = If(distLeft <= distRight, Edge.Left, Edge.Right)
Dim verticalDist = Math.Min(distLeft, distRight)
' Tie goes to vertical edge to preserve original behavior
Return If(horizontalDist < verticalDist, horizontalEdge, verticalEdge)
End Function
Private Shared Function ComputeLeaderPoint(edge As Edge, midPoint As Point2d, top As Double, bottom As Double, left As Double, right As Double, balloonDiameter As Double) As (X As Double, Y As Double)
Select Case edge
Case edge.Top
Return (midPoint.X + balloonDiameter / 2, top + balloonDiameter)
Case edge.Bottom
Return (midPoint.X + balloonDiameter / 2, bottom - balloonDiameter)
Case edge.Left
Return (left - balloonDiameter, midPoint.Y + balloonDiameter / 2)
Case Else ' Edge.Right
Return (right + balloonDiameter, midPoint.Y + balloonDiameter / 2)
End Select
End Function
Private Class Placement
Public Property TagCurve As TagCurve
Public Property MidPoint As Point2d
Public Property ChosenEdge As Edge
Public Property LeaderX As Double
Public Property LeaderY As Double
End Class
Public Class TagCurve
Public Sub New(drawingCurve As DrawingCurve)
Curve = drawingCurve
EdgeProxy = drawingCurve.ModelGeometry
Occ = EdgeProxy.ContainingOccurrence.OccurrencePath.Item(1)
FileName = Occ.ReferencedFileDescriptor.FullFileName
End Sub
Public Property FileName As String
Public ReadOnly Property Curve As DrawingCurve
Public Property DistanceToNearestViewEdge As Double
Private ReadOnly EdgeProxy As EdgeProxy
Public Occ As ComponentOccurrence
End Class
End Class
This article was published first at the autodesk blog:
https://forums.autodesk.com/t5/community-blog-d-m-english/a-different-approach-to-auto-balloon/ba-p/14140551