We were trying to modify the return diffuser family so that it masks the ceiling that it is mounted in. The family is a series of model lines drawn on the face of the ceiling.
I can create a masking region, but if I set it to the same plane as the ceiling, it doesn't mask the ceiling. If I set it to a workplane below the ceiling, it masks the ceiling, but it also masks the lines of the family that I want to see.
It seems that the problem is that a masking region will not mask a surface pattern if it is drawn in the same plane as the surface. I would like it better if masking regions would draw with some type of display order to show the lines from the family that are draw in the same plane, but hide the model elements in the same plane.
Thoughts? Is this the case or am I missing something?