[v8i vba] Detect if shapes are coplanar?

Unknown said:

I cannot find a function that tells me if either:

1. Two shapes are coplanar, or
2. Two plane3d are coplanar

We wrote a VBA project answering your question that is explained in this article.

Unknown said:

From what I read, the essence is that we have to do math.  Do I really need to do math?

No: in this case MicroStation VBA does the hard work for you.  However, you need to understand the geometric 3D concepts of points, planes and normals for the solution to make sense.

Hi Guys,

Wow! Thanks for all the nice work. I am sure that will save a few future math-questions around here! :)
As stated earlier I went with this semi built-in functionality:

Function isCoplanar(a As Element, b As Element) As Boolean

    On Error Resume Next

    isCoplanar = True
    
    Dim aa(0) As Element
    Set aa(0) = a
    Dim ab(0) As Element
    Set ab(0) = b
    
    GetRegionUnion aa, ab, Nothing
    If Err.Number <> 0 Then
        isCoplanar = False
        Err.Clear
    End If
    
    Erase aa
    Erase ab
    
End Function

Hi Guys,

Wow! Thanks for all the nice work. I am sure that will save a few future math-questions around here! :)
As stated earlier I went with this semi built-in functionality:

Function isCoplanar(a As Element, b As Element) As Boolean

    On Error Resume Next

    isCoplanar = True
    
    Dim aa(0) As Element
    Set aa(0) = a
    Dim ab(0) As Element
    Set ab(0) = b
    
    GetRegionUnion aa, ab, Nothing
    If Err.Number <> 0 Then
        isCoplanar = False
        Err.Clear
    End If
    
    Erase aa
    Erase ab
    
End Function