I would like to cut a shape out of a surface mesh using a polygon.
The "Knife Project" function isn't working for me, as it changes the size of the polygon. When it projects the polygon down onto the surface mesh, it increases the size of the polygon by some amount, depending on how far away my viewpoint is.
In this example, I want to project the polygon directly downwards, such that the polygon that is cut is exactly the same as the polygon that I started with.
I would also like to discard the outside of the cut, not the inside. I.e. I'm not trying to cut a hole, I'm trying to trim off edges.