I am trying to create some ceilings under a barrel vault and I have run into a couple of issues. See attached screen captures for reference.
Issue 1. Ceiling A is intended to be the ceiling for the underside of the barrel vault roof. I created it as an extruded ceiling following the shape of the roof. I cannot trim the edge to match the parabola created at the intersection of the barrel vault and the main roof. A roof created by extrusion can be edited in plan using the "edit plan outline" (might not be the exact name) option. For some reason this option does not exist for extruded ceilings. I also tried to create a void to cut the ceiling with but when I try to use the "cut geometry" tool it won't let me selected the extruded ceiling (I can select the "standard" ceilings.) I guess that I could make an extruded roof out of gypsum board for the ceiling but then I won't be able to use ceiling based light fixtures.
Issue 2. Ceiling B follows the underside of the main roof at a 4"/12" slope. I tried to use the "opening" tool to cut the parabola shape out of that ceiling without success. I can use the "pick line" option to create the parabola portion of the opening sketch but the ends of the parabola extend past the edge of the ceiling which is to be cut by it. If I highlight the parabola the drag controls become active but dragging the ends to connect with the ceiling edge lines causes the parabola to change shape slightly. The "trim" command won't cut the parabola either.