How to define a polygon part in a rectangle?

[JosiahMaybe]

Okay so I have this 3d thing, it projects to 2d view plane via view point and XYZ view plane definition. I can define a rectangle like shape by xmin, ymin, xmax, and ymax in 2d. It may also be a point or line that rectangle like thing. What I am really trying for is approximate intersect of 2 2d shapes for 3d draw order. That rectangle like thing is common rectangle of both shapes sort of.

I know centroids, projection, intersection, inside outside algorithm for rectangle and other stuff. All points are with real, finite numbers. Polygons are not self intersecting. There may be a rectangle entirely in or out of a polygon. I handle anything in 2d collinear entirely already. What I have trouble with is like that bottom left corner of top left intersection. How to determine when to use parts of rectangle as vertices in a shape and which?

I already have a minimums and maximums at x or y intercepts with rectangle thing so I can find which side mostly on but not exactly. I know this is a mathy question. Feel free to remove it if needed. Are there any free resources on this? Thanks for whatever you may help with. Is there an existing algorithm I could study? X E.

 

[JosiahMaybe]

Okay, solved I guess, like have 4 points, one for mins, two min max, and one maxes, get bounds inside rectangle, if a point outside rectangle is more in a way from center of rectangle move toward it as much as is in bounds of rectangle. If a line intersects x or y like that, move toward intersect like that. Should give an accurate 2d approximation. X E.