Hi!
Look at View3D.GetOrientation() method. This is from RevitLookup (very useful tool):
See also about camera positioning in 3dViews: https://knowledge.autodesk.com/search-result/caas/CloudHelp/cloudhelp/2017/ENU/Revit-API/files/GUID-A7FA8DBC-830E-482D-9B66-147399524442-htm.html
