Triangulation

[Mauro Dallapina]

Hello,
I'm a new CAD2Shape user and I'm using your software to translate a 3D DWG file into a SHP file.
When I convert the original drawing to a Polygon SHP, I see that all the polygons in the CAD drawing are split into triangles.
Is this behaviour optional or mandatory? In the former case, how can I unset this feature?

Thanks,
Mauro

[GuthCAD Software Support]

Hi Mauro,

If you are converting to a Polygon SHP file generally you should not get triangulation. It may happen if the AutoCAD polygons are originally triangulated. For example our own Arcv2CAD software triangulates SHP polygons when converting to AutoCAD Rel 12 DXF or DWG, because that version of AutoCAD did not support multi-sided polygon surfaces.

If possible please send me a sample drawing via a Private Message so that we can give a better answer.

Thanks!
Software Support

[GuthCAD Software Support]

Hi Mauro,

Thanks for sending the DWG.

The reason for the triangulation for this drawing is that the buildings have been drawn using PolyfaceMesh entities. A PolyfaceMesh entity (Polyface = multiple faces) by the AutoCAD definition requires that each face of the entity must only have 3 or 4 vertices. The PolyfaceMesh entities in your drawing have been defined with 3 vertices per face. CAD2Shape is just outputting each face as it has been defined in the drawing.

However we concede that it would be nice to merge such faces to a single surface, and so have scheduled to add such an option in CAD2Shape, hopefully in the next software update in a week or so. We will post a notice to this thread when it is ready.

Best regards,
Software Support

[GuthCAD Software Support]

Hi,


We have now posted a new software update to our download page.

CAD2Shape 3.0 A.29 (http://www.guthcad.com/download_cad2shape.htm)
To get the output without triangulation select:

Shapefile type = Polyline Shapefile
Entities = Polygon Mesh / PolyFace Mesh
'Translate visible edges only ...' = on

We initially hoped to make it so that we could get a similar results for the Polygon Shapefile type, but realized that it is quite hard, and a very specialized requirement (i.e. not a general requirement.)

Note that because each building is defined with visible edges at the ground level and also at the height of the building, there will be 2 polylines on top of each other (at the 2D level). I.e. duplicate polyline shapes (except for the 'Elevation' attribute value if it was selected for translation.) Duplicate polylines may also be created
because of the fact that each building may be composed of several PolyFace Mesh entities. At the join of one PolyFace Mesh entity to another PolyFace Mesh entity, the joining edge may be marked as 'visible' in both PolyFace Mesh entities, thus producing 2 Polyines.

best regards,
Software Support