[abenedik]

I am not sure that I fully understand your question.

If you want to combine all the meshes into one mesh, then you can use the Ab3d.Utilities.MeshUtils.CombineMeshes method - it takes a collection of MeshGeometry3D objects and creates a single MeshGeometry3D object.

But if you wanted to export only one model instead of all, then you can call AddModel or AddVisual3D instead of AddViewport3D - see code from sample:

            // First create an instance of AssimpWpfExporter
            var assimpWpfExporter = new AssimpWpfExporter();

            // We can export Model3D, Visual3D or entire Viewport3D:
            //assimpWpfExporter.AddModel(model3D);
            //assimpWpfExporter.AddVisual3D(ContentModelVisual3D);
            //assimpWpfExporter.AddViewport3D(MainViewport);




I do not understand what do you mean by "I also need to create a filled (solid)  mesh suitable for 3d printing.". The MeshGeometry3D object already represents a solid mesh - it is created from filled triangles. Is this not ok?