Never before had a problem with lighting on my 3D models or assemblies. Always used the default lighting you get when you start a new drawing with the wizard. Always able to tip the model with "real time motion", and see the underside.
Yesterday I created a mechanical assembly with V17. The top of the assembly is illuminated just like normal. But if I tip it to look at anything on the underside, it is totally dark. Can't see a thing. I tried placing a light below (flashlight). That helped somewhat. But then I noticed that nothing is visible on the edges. They are dark too. Do I need to shine a flashlight at each edge, and WHY?" What has changed?