when we need some complex shape tensile roof of reinforced concrete or any other material to model it and to get analytical model for FEM analysis (goal is to model an analytical surface of that shape) but in Revit you can't do that because of the limitations of analytical model of floor slab or foundation slab or structural wall. Dlubal RFEM have that functionality but revit don't. We can't make surface like a tensile membrane having analytical model in revit but we only manage to make 3D mass or 3D model of a membrane somehow by massing techniques or advanced modeling technique but all fails when we need export analytical geometry for Finite Element Analysis. Couldn't it be impossible in revit?