AutoCAD MEP Wishes

[#1]

Can anybody tell me where I'm wrong here? I am trying to use the MEP Design display config to show my ductwork with hidden lines when ducts cross each other. This seems to work alright unless I bring the "Cut Plane" into the equation.

I have hidden lines showing up that are clearly above and below the display range that I created. I also have the sides of vertical ductwork not showing when it runs from withing the display range to outside of it.

You would think that the Cut Plane would NOT show ANYTHING that is above or below the display range and that it would show EVERYTHING that is in the display range.

Is there any reason why it doesn't?

I have included a pdf with 2 pages showing my issues.

[#2]

I know this is an old post, but the cut plane only works on mep objects when the Enable display by elevation option is checked.  You can find this under Options-> MEP Display Control.  It is the last item on the page.  Once enabled, the cut plane will work its magic.  I would look up display by elevation in the help file so you can understand exactly what the cut plane does and how to display duct in the 4 different zones created by using the cut plane.