I need something like impoly that works in 3d. I imagine the polygon being drawn on a plane at right angles to the view direction and in front of everything else in the axes object, the result being the positions of the vertices in that plane's frame of reference, together with a transformation from there to the axis frame. Does anything like this exist?
In my intended application, there are no images present, 2d or 3d, just patches that I will be projecting the selected polygon over.
If it were possible to have a transparent axes object overlying another and use impoly on the first in front of my graphics in the second, that could work, but I don't think an axes can be transparent.