Q:
The RangeBox property returns an axis aligned bounding box. In the case the component is rotated 45deg around Z axis for example, it will return a rather bigger bounding box than the tight box of the component.
A:
The range box is not always a tight fitting box. It’s always axis aligned with the document axes system you’re working in. The intent of the range box is to provide an easily calculated box that contains the object in question. This box can then be used as part of a pre-sorting algorithm to find or reject objects that cross a particular boundary. It’s not intended to always tightly enclose an object. A reasonably tight fitting bounding box is computed for the part aligned with the part’s coordinate system and cached in the part.
An occurrence bounding box takes this part box (not the part geometry), transforms it into the assembly space, and then fits a new box aligned with the assembly coordinates. Of course if there is a non orthogonal rotation between part and assembly space, the assembly box will be larger than the box in part space to fit around it. This is an optimization in order to avoid re-computing the part geometry bound in arbitrary assembly contexts.
Returning the optimal (aligned to principle geometry axis) or necessarily tight fitting bounds, is not a requirement for this API, but to return a reasonable bounding box that is only guaranteed to completely contain the geometry. If you want an assembly’s tight fitting box, iterating the edges and calculating the min/max point through every edge.Evaluator.RangeBox could be one approach. But the better solution is to calculate min and max points from existing facets instead of edges. This will always give tight bounding box in assembly and part context irrespective of shape (imagine something like a sphere where the edge tessellations would not be useful to determine bounds).
The following sample code demonstrates the approach, and draws a range box (client graphics) that tightly encloses the part component.
Keep in mind that the bound could be too small by the chordal deviation tolerance you use, so you may need to inflate the box by the tolerance to be safer. The above sample didn’t add tolerance to inflate the box, please note that you need to do it according to your actual requirement.
Public Sub FindRangeBoxWithFacet(ByVal app As Inventor.Application)
Dim oDoc As AssemblyDocument
oDoc = app.ActiveDocument
‘ Set a reference to component definition of the active document.
‘ This assumes that a part or assembly document is active.
Dim oCompDef As AssemblyComponentDefinition
oCompDef = app.ActiveDocument.ComponentDefinition
Dim aoRanges As Box = Nothing
If oCompDef.Occurrences(1).SurfaceBodies.Count > 0 Then
‘ Set a reference to the body of the part.
Dim oBody As SurfaceBody
oBody = oCompDef.Occurrences(1).SurfaceBodies.Item(1)
Dim iVertexCount As Integer
Dim iFacetCount As Integer
Dim adVertexCoords(0) As Double
Dim adNormalVectors(0) As Double
Dim aiVertexIndices(0) As Integer
‘ Determine the highest tolerance of the existing facet sets.
Dim ToleranceCount As Long
Dim ExistingTolerances(0) As Double
Call oBody.GetExistingFacetTolerances(
ToleranceCount, ExistingTolerances)
Dim i As Long
Dim BestTolerance As Double
For i = 0 To ToleranceCount – 1
If i = 0 Then
BestTolerance = ExistingTolerances(i)
ElseIf ExistingTolerances(i) < BestTolerance Then
BestTolerance = ExistingTolerances(i)
End If
Next
Call oBody.GetExistingFacets(
BestTolerance,
iVertexCount,
iFacetCount,
adVertexCoords,
adNormalVectors,
aiVertexIndices)
Dim cn As Long
Dim minPt As Point
Dim maxPt As Point
For cn = LBound(adVertexCoords) To UBound(adVertexCoords) Step 3
‘ The Range box can be identified by the fact that the aoRanges
‘ variable will still be Nothing.
If aoRanges Is Nothing Then
‘Initialize the range box with the first vertex
aoRanges = app.TransientGeometry.CreateBox
Dim firstPt(2) As Double
firstPt(0) = adVertexCoords(cn)
firstPt(1) = adVertexCoords(cn + 1)
firstPt(2) = adVertexCoords(cn + 2)
Call aoRanges.PutBoxData(firstPt, firstPt)
Else
minPt = aoRanges.MinPoint
maxPt = aoRanges.MaxPoint
If (minPt.X > adVertexCoords(cn)) Then
minPt.X = adVertexCoords(cn)
End If
If (minPt.Y > adVertexCoords(cn + 1)) Then
minPt.Y = adVertexCoords(cn + 1)
End If
If (minPt.Z > adVertexCoords(cn + 2)) Then
minPt.Z = adVertexCoords(cn + 2)
End If
aoRanges.MinPoint = minPt
If (maxPt.X < adVertexCoords(cn)) Then
maxPt.X = adVertexCoords(cn)
End If
If (maxPt.Y < adVertexCoords(cn + 1)) Then
maxPt.Y = adVertexCoords(cn + 1)
End If
If (maxPt.Z < adVertexCoords(cn + 2)) Then
maxPt.Z = adVertexCoords(cn + 2)
End If
aoRanges.MaxPoint = maxPt
End If
Next
End If
‘ Check to see if range box graphics information already exists.
Dim oClientGraphics As ClientGraphics
Dim oLineGraphics As LineGraphics
Dim oBoxNode As GraphicsNode
Dim oGraphicsData As GraphicsDataSets
Try
oGraphicsData = oDoc.GraphicsDataSetsCollection("RangeBoxGraphics")
oClientGraphics = oCompDef.ClientGraphicsCollection
("RangeBoxGraphics")
oGraphicsData.Delete()
oClientGraphics.Delete()
Catch ex As Exception
End Try
‘ Create a graphics data set object. This object contains all of the
‘ information used to define the graphics.
Dim oDataSets As GraphicsDataSets
oDataSets = oDoc.GraphicsDataSetsCollection.Add("RangeBoxGraphics")
‘ Create a coordinate set.
Dim oCoordSet As GraphicsCoordinateSet
oCoordSet = oDataSets.CreateCoordinateSet(1)
‘ Create the client graphics for this compdef.
oClientGraphics = oCompDef.ClientGraphicsCollection.Add
("RangeBoxGraphics")
‘ Set a reference to the transient geometry object for user later.
D
im oTransGeom As TransientGeometry
oTransGeom = app.TransientGeometry
‘ Create a graphics node.
oBoxNode = oClientGraphics.AddNode(1)
oBoxNode.Selectable = False
‘ Create line graphics.
oLineGraphics = oBoxNode.AddLineGraphics
oLineGraphics.CoordinateSet = oCoordSet
Dim dBoxLines(12 * 6 – 1) As Double
Dim MinPoint(2) As Double
Dim MaxPoint(2) As Double
Call aoRanges.GetBoxData(MinPoint, MaxPoint)
‘ Line 1
dBoxLines(0) = MinPoint(0)
dBoxLines(1) = MinPoin
t(1)
dBoxLines(2) = MinPoint(2)
dBoxLines(3) = MaxPoint(0)
dBoxLines(4) = MinPoint(1)
dBoxLines(5) = MinPoint(2)
‘ Line 2
dBoxLines(6) = MinPoint(0)
dBoxLines(7) = MinPoint(1)
dBoxLines(8) = MinPoint(2)
dBoxLines(9) = MinPoint(0)
dBoxLines(10) = MaxPoint(1)
dBoxLines(11) = MinPoint(2)
‘ Line 3
dBoxLines(12) = MinPoint(0)
dBoxLines(13) = MinPoint(1)
dBoxLines(14) = MinPoint(2)
dBoxLines(15) = MinPoint(0)
dBoxLines(16) = MinPoint(1)
dBoxLines(17) = MaxPoint(2)
‘ Line 4
dBoxLines(18) = MaxPoint(0)
dBoxLines(19) = MaxPoint(1)
dBoxLines(20) = MaxPoint(2)
dBoxLines(21) = MinPoint(0)
dBoxLines(22) = MaxPoint(1)
dBoxLines(23) = MaxPoint(2)
‘ Line 5
dBoxLines(24) = MaxPoint(0)
dBoxLines(25) = MaxPoint(1)
dBoxLines(26) = MaxPoint(2)
dBoxLines(27) = MaxPoint(0)
dBoxLines(28) = MinPoint(1)
dBoxLines(29) = MaxPoint(2)
‘ Line 6
dBoxLines(30) = MaxPoint(0)
dBoxLines(31) = MaxPoint(1)
dBoxLines(32) = MaxPoint(2)
dBoxLines(33) = MaxPoint(0)
dBoxLines(34) = MaxPoint(1)
dBoxLines(35) = MinPoint(2)
‘ Line 7
dBoxLines(36) = MinPoint(0)
dBoxLines(37) = MaxPoint(1)
dBoxLines(38) = MinPoint(2)
dBoxLines(39) = MaxPoint(0)
dBoxLines(40) = MaxPoint(1)
dBoxLines(41) = MinPoint(2)
‘ Line 8
dBoxLines(42) = MinPoint(0)
dBoxLines(43) = MaxPoint(1)
dBoxLines(44) = MinPoint(2)
dBoxLines(45) = MinPoint(0)
dBoxLines(46) = MaxPoint(1)
dBoxLines(47) = MaxPoint(2)
‘ Line 9
dBoxLines(48) = MaxPoint(0)
dBoxLines(49) = MinPoint(1)
dBoxLines(50) = MaxPoint(2)
dBoxLines(51) = MaxPoint(0)
dBoxLines(52) = MinPoint(1)
dBoxLines(53) = MinPoint(2)
‘ Line 10
dBoxLines(54) = MaxPoint(0)
dBoxLines(55) = MinPoint(1)
dBoxLines(56) = MaxPoint(2)
dBoxLines(57) = MinPoint(0)
dBoxLines(58) = MinPoint(1)
dBoxLines(59) = MaxPoint(2)
‘ Line 11
dBoxLines(60
) = MinPoint(0)
dBoxLines(61) = MinPoint(1)
dBoxLines(62) = MaxPoint(2)
dBoxLines(63) = MinPoint(0)
dBoxLines(64) = MaxPoint(1)
dBoxLines(65) = MaxPoint(2)
‘ Line 12
dBoxLines(66) = MaxPoint(0)
dBoxLines(67) = MinPoint(1)
dBoxLines(68) = MinPoint(2)
dBoxLines(69) = MaxPoint(0)
dBoxLines(70) = MaxPoint(1)
dBoxLines(71) = MinPoint(2)
‘ Assign the points into the coordinate set.
Call oCoordSet.PutCoordinates(dBoxLines)
‘ Update the display.
app.ActiveView.Update()
End Sub
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p style=”line-height: normal;margin: 0in 0in 0pt” class=”MsoNormal”>
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