I was asked to quote a file repair job for a student that had access to a 3D printer. To save him money (because we have a soft spot for students) I offered to show him how to prep the SketchUp file for free.
The model looked good in SketchUp, and appeared to have no reversed Normals (backward facing surfaces), but it contained an amazing number of open edges, which is typical for Sketchup Models.
Depending on the type of model you are attempting to print, you may be able to simply send the model up to CADspan and have it take care of everything. In the case of this model, I would segment the model first to retain every bit of detail possible. Because this model is obviously a collection of separate buildings on a base, I would separate the buildings one by one and process the base separately, or slice the base in to pieces the carry over with each building. If you opt to cut the model, adding a large plane, selecting it, right clicking ad choosing intersect with model, can help to create all of the necessary surfaces. The CADspan Unsmooth Model tool can also help to subdivide curved surfaces, but be aware that it can take a long time to complete and is not easily undone for rendering purposes.
I took the segment that I had indicated in blue and separated it from the larger model. You can do this by simply grouping this selection independently, but I would suggest actually cutting it from the larger model entirely and paste-in-place in to a new model window to avoid SketchUp layer, group and component issues that could arrise.
Once you have a manageable chunk of the model in a separate file, you can fill any holes that were created when you separated this piece. You can see two large holes in the upper left and lower right area along the cutting plane in the above example.
The CADspan resurfacer will eliminate a number of CAD issues automatically, but not all of them. CADspan will eliminate coplanar faces, reversed normals, any stray 2D lines leftover in the model and can take care of small holes. CADspan will not necessarily take care of 2D faces in the model. These can cause issues, especially if you are intending for these faces to actually resolve in to a physical object in the 3D Print. All 2D faces that are floating in the model should be addressed and I would suggest filling any holes you find in the model to allow CADspan to produce the cleanest possible model. This process can take time, but will yield the best result.
More to come...