Revit uses daylight portals differently from 3ds Max. They exist in both applications but because they are calculated differently when you render, 3ds Max FBX Plug-in does not import these daylight portals into 3ds Max. Doing so would result in low performance. This performance issue is because Revit systematically creates daylight portals for each individual window, and for each side of the window. This does not affect the rendering performance of Revit since only windows relevant to the camera view are only calculated when you render.
However, 3ds Max renders all daylight portals systemically. Therefore, it is better to create one single daylight portal for an entire wall of windows manually in 3ds Max as you would normally when you work in 3ds Max. This results in better performance and gives better visual results.
