我想计算将面域的形心移动到0，0点然后计算惯性矩，可奇次和偶次计算结果不一样
我想计算将面域的形心移动到0，0点然后计算惯性矩，可奇次和偶次计算结果不一样，具体的说就是形心坐标第偶次计算又回到初始的位置：（，程序如下Private Sub CommandButton1_Click()
UserForm1.Hide
Dim currUCS As AcadUCS
Dim origin(0 To 2) As Double
Dim Centroid As Variant
Dim momentOfInertia As Variant
Dim sset As AcadSelectionSet 'Define sset as a SelectionSet object
'Set sset to a new selection set named SS1 (the name doesn't matter here)
Set sset = ThisDrawing.SelectionSets.Add("SS1")
sset.SelectOnScreen 'Prompt user to select objects
Dim ent As Object 'Define ent as an object
For Each ent In sset 'Loop through the SelectionSet collection
If ent.EntityName = "AcDbRegion" Then
Centroid = ent.Centroid
' Create a UCS and makes it current
Set currUCS = ThisDrawing.ActiveUCS
origin(0) = Centroid(0): origin(1) = Centroid(1): origin(2) = 0
currUCS.origin = origin
ThisDrawing.ActiveUCS = currUCS
momentOfInertia = ent.momentOfInertia
MsgBox "Ix=" & Format(momentOfInertia(0) / 10000, "######.00") & "mm^4；Iy=" & Format(momentOfInertia(1) / 10000, "######.00") & "mm^4", , "被选择物体的惯性矩"
End If
Next ent
sset.Delete
UserForm1.Show
End Sub
origin的原因
通过单步调试，我发现奇次和偶次计算时，currUCS.origin和ThisDrawing.ActiveUCS.origin不一样，暂未找到解决办法，有空我再试试。快来帮忙呀：（
帮我调试调试，我做不出来。找到原因了,先这样解决
本帖最后由 作者 于 2002-7-16 16:03:03 编辑找到原因了，Thisdrawing.ActiveUCS是活动UCS而不是系统UCS，计算转动惯量时以Thisdrawing.ActiveUCS的原点为中心，第一次运行时，以面域形心(注意：形心坐标非零，即不是系统UCS原点)为惯性中心;第二次运行时，形心坐标计算以Thisdrawing.ActiveUCS为参照，为零，惯性中心为(0,0)即系统UCS原点与面域形心不同。
解决办法：在修改Thisdrawing.ActiveUCS前保存原点，MsgBox后恢复。请参考以下代码。
Private Sub CommandButton1_Click()
UserForm1.Hide
Dim temp(0 To 2) As Double
Dim origin(0 To 2) As Double
Dim Centroid As Variant
Dim currUCS As AcadUCS
Dim momentOfInertia As Variant
Dim sset As AcadSelectionSet 'Define sset as a SelectionSet object
'Set sset to a new selection set named SS1 (the name doesn't matter here)
Set sset = ThisDrawing.SelectionSets.Add("SS1")
sset.SelectOnScreen 'Prompt user to select objects
'save current UCS origin
temp(0) = ThisDrawing.ActiveUCS.origin(0)
temp(1) = ThisDrawing.ActiveUCS.origin(1)
temp(2) = ThisDrawing.ActiveUCS.origin(2)
Dim ent As Object 'Define ent as an object
For Each ent In sset 'Loop through the SelectionSet collection
If ent.EntityName = "AcDbRegion" Then
Centroid = ent.Centroid
' Create a UCS and makes it current
Set currUCS = ThisDrawing.ActiveUCS
origin(0) = Centroid(0): origin(1) = Centroid(1): origin(2) = 0
currUCS.origin = origin
ThisDrawing.ActiveUCS = currUCS
momentOfInertia = ent.momentOfInertia
MsgBox "Ix=" & Format(momentOfInertia(0) / 10000, "######.00") & "mm^4；Iy=" & Format(momentOfInertia(1) / 10000, "######.00") & "mm^4", , "被选择物体的惯性矩"
End If
Next ent
currUCS.origin = temp
ThisDrawing.ActiveUCS = currUCS'restore ActiveUCS origin
sset.Delete
UserForm1.Show
End Sub
thx
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