Hi Bernard
Thanks for sending us the DXF file to look at.
The first thing I try in situations like this is to delete all the unrequired entities in a CAD program. For this I used the free edition of Draftsight. Then save out this other copy with only the details needed.
I tried creating a Kubla Cubed project and the results look OK although I would say they could benefit from some tidying up by adding additional break lines and contours in Kubla Cubed. The existing has gaps in elevation data especially around the demolition areas (not sure what they are but the recessed pads) that cause nasty triangulation artifacts. If you were to trace a break line or contour around the base of the demo areas it would look nicer.
Also the proposed seems to sometimes have better detail in some areas than others.
Did you know that Kubla Cubed now supports importing triangulations. Do you use Bentley ? You might find instead of exporting these breaklines you can export a LandXML surface and then import into Kubla Cubed as a Triangle Surface. The only downside in this method is you cannot edit it further in Kubla Cubed.
In regard to the overall issue we are going to be investing in superior CAD import technology soon. Expect .DWG and .DGN support soon.
