A standard breakline consists of an array of 3D lines or polylines. Each line endpoint becomes a point in the surface and surface triangles around the breakline are redone. If the polyline contains curves, then the curve is tessellated based on the mid-ordinate distance parameter.
' Create the polyline basis for the breakline. Dim o3DPoly as Acad3DPolyline Dim dPoints(0 To 8) As Double dPoints(0) = 1200: dPoints(1) = 1200: dPoints(2) = 150 dPoints(3) = 2000: dPoints(4) = 3000: dPoints(5) = 120 dPoints(6) = 3000: dPoints(7) = 2000: dPoints(8) = 100 Set o3DPoly = oAeccDocument.Database.ModelSpace _ .Add3DPoly(dPoints) o3DPoly.Closed = False Dim oBreakline As AeccSurfaceBreakline Dim vBLines As Variant ' This has to be an array, even if we only have one entity. Dim oEntityArray(0) As AcadEntity Set oEntityArray(0) = oAeccDocument.Database.ModelSpace _ .Add3DPoly(dPoints) Set oBreakline = oTinSurface.Breaklines.AddStandardBreakline _ (oEntityArray, "Sample Standard Break", 1#)