Robert, thanks for these insights, you really clarified many things for me and both my model and my visualization start to look very promising. The tutorial data has helped me out a lot and so has the Service Pack I downloaded to take care of some of the recurring bugs.
Still a few challenges on the way, however, as I'm still not able to run the model succesfully (nor can I swap my 3D network and use the tutorial model). There seems to be some kind of problem with the Add Locations tool still, since its executing gives me errors 030046 (Could not construct locator feature agents for the network) and 030003 (Failed to create locator from agents). Because of these errors, the model fails while trying to execute Add Locations. I've triple-checked my model so that it should work like the one in the tutorial, and I don't know what to do next.
I was wondering if you would have any ideas on how to do some troubleshooting with this? If adding locations is the problem, could it have something to do with my network dataset itself?
At some point I managed to execute the 3D routing succesfully once, but since then the model has not cooperated again. I feel I'm close to solving this small task, but irritatingly enough I don't know how to do it. Any help appreciated! Again, thanks!