I use Blender to produce small props for Daz scenes. Recently, I made a test tube rack for a chem lab scene, exported it from Blender as an .obj file, then imported it into Daz Studio, to find that the holes for the tubes had been filled with extra polygons. The obj file imports back into Blender and into Photoshop CC 3D without any problems which is why I am posting this in the Daz forum. Can anybody help with this? I am using Blender 2.8 and Daz Studio 4.10. The images are the original model(background) re-imported obj file ( foreground) in Blender and the imported obj in Daz Studio.

The problem is that the areas around the holes are n-gons (polygons with - many - more than four vertices). Not only that but they are concave - if you snap an elastic band around the polygon it will not follow the actual polygon but will leave a gap. The mesh will work, albeit with a higher ploygon count, if you triangulate those sections (or rework the mesh in some other way).

Triangulation worked. Many thanks. The holes were formed using a boolean operation, which is something I have normally avoided in Bender because before version 2.8 the boolean operations did not work very well. This is probably why I have not encountered the problem before.

Yes, unfortunately Booleans are very prone to leaving n-gons and the like behind them.

Just out of interest is there any reason why Daz Studio should be prone to n-gon problems. As I said above, the effect was not seen in Blender, Photoshop 3D, or Hexagon

Sorry, I have only a hazy idea of the details involved - trying to answer would probably end up giving a lot of incorrect information..

N-gons often only make sense to the program they originated in because the program has extra information about them that many common export formats don't support.