A Multipatch is consideret to be closed if the Volume property of the Multipatch (from the IVolume interface) is not equal to zero. However, this property describes the enclosed volume of the Multipatch so it would be non-zero in case of highly deviated shapes too (twisted cubes, wrong direction/rotation of the triangles).
Here is a sample code:
Dim Points As PointClass() = New PointClass() _
{New PointClass() With {.X = 10.0#, .Y = 10.0#, .ZAware = True, .Z = 0.0#},
New PointClass() With {.X = 10.0#, .Y = 0.0#, .ZAware = True, .Z = 0.0#},
New PointClass() With {.X = 0.0#, .Y = 10.0#, .ZAware = True, .Z = 0.0#},
New PointClass() With {.X = 0.0#, .Y = 0.0#, .ZAware = True, .Z = 0.0#},
New PointClass() With {.X = 0.0#, .Y = 0.0#, .ZAware = True, .Z = 10.0#},
New PointClass() With {.X = 10.0#, .Y = 0.0#, .ZAware = True, .Z = 10.0#},
New PointClass() With {.X = 10.0#, .Y = 10.0#, .ZAware = True, .Z = 10.0#},
New PointClass() With {.X = 0.0#, .Y = 10.0#, .ZAware = True, .Z = 10.0#}}
Dim Triangles As New TriangleStripClass() With {.ZAware = True}
For Each N As Integer In New Integer() {0, 1, 2, 3, 4, 1, 5, 6, 4, 7, 2, 6, 0, 1}
Triangles.AddPoint(Points(N))
Next
Dim Multipatch As New ESRI.ArcGIS.Geometry.MultiPatchClass() With {.ZAware = True}
Multipatch.AddGeometry(Triangles)
Ákos Halmai
