Apologies for the lack of example code, I'm currently in the brainstorming phase of the problem and having trouble finding a proper solution.
As I have stated in my title, I want to find out what the intersection area of two polygon are. To be more specific, I have two ARPlane's that may overlap each other on the x-z plane but be on different y-levels (imagine stairs with an overhang). I can get the area boundaries of these ARPlanes easily. My first idea to simplify the process is to remove the y-component so as to have them on the same plane and turn this into a 2D problem.
From here onward, I'm unsure of how to proceed. I could not find any methods that calculated the intersection areas of two polygons. I have a few solutions that look promising if I can get the planes aligned neatly (such that the +x direction points from the center of one of the planes to the other), but I cannot move them in any way so I must modify what the local "forward" for a plane is. Even then, I don't think the ARPlane has a direction vector in the first place as they are not GameObjects, so I am unsure if this is a viable option as a path to follow. ARPlane class for quick reference.
One other way is to turn the planes so that they're in alignment with world x axis. This looks promising over the other methods but as I previously stated, I cannot turn the actual ARPlanes. I must make a copy of them and turn the copies while keeping their relative rotations and positions the same.
So far these have been the methods I could come up with but could not develop fully due to unity restrictions. My question, then, is whether there is a way to get around the issues of these problems; failing that, whether there is an alternative solution to the issue that can be recommended.
Below is an example use case of the tool. As can be seen, some stair threads have an overhang that covers a portion of the previous thread's surface (second and third figure). Each stair thread will be scanned and then processed to find their usable surface. The area covered by the overhang is not a usable surface. This usable area is defined by the placements of a staircase thread (A), and the very next thread right above it (B); so then the usable area will be surface_area_of_A - xz_crossSection_of_AB
