Top-view shape of rotated 3D objects?

Hello, this is a math question

In ROBLOX, object's sizes are in Vector 3. When their Rotation is 0,0,0, what you see from the top is basically X by Z. From the bottom, same thing, from the front, X by Y (or Z by Y, depends), etc.

However, if you rotate the object on either the X or Z axis (it wont change with Y axis), the shape you'll see from the TOP will change because you'll be seeing two different surfaces.

Is there a way to calculate the shape of what you'll see from the top, using the X,Y,Z size and rotations? I know it's TECHNICALLY do-able with raycasting but I'm looking for precision. I don't know how to calculate that.

Something I did notice is if your 3D object is a cube, it'll never change. Use that as a mainline, I guess.