I am converting shapefile model of buildings in LoD2 to CityGML. In CityGML really matter about poylgon orientation(Countercloskwise can be seen from outside, Clockwise from inside). I have problem with orientation of some polygons. Althought I've set almost every polygon to right direction, there still remain some of them to orientate. I know that in 2D it's pretty much easy task, but it changes by going to 3D (polygonZ). Is there some kind of tool, which can solve this task straight forward?
For most closed surfaces, you can work out the center (or some point that falls "inside") and use that to determine what is "outside", and what the final direction the normal should take.
For irregular solids that have surfaces within their convex hull (like an "E" shape), they need to be broken down into combination of smaller objects (like cubes) for the basic approach to work.