I know that video and that's why i'm saying it's 2d. But now i am confused.
The map is a flat surface on which the characters walk upright on, but the space is 3D. Imagine a rectangular room with no walls in which you are standing up, the edges of the room where the walls are supposed to be are the edges of the painted map. This is what each level in PoE is, a 3D room without walls. The magic comes into play when the camera has a fixed perspective and you are looking from a particular angle at the floor on which the map is painted. Yes, the map itself is obviously 2D, in that it's painted on a flat surface, but the actual game is entirely 3D because of that room. It's kind of hard to explain without the video.
Ok i got it now, so basically most of 3d is empty active space right? Doesn't this make the 2d element (huge map) the biggest and resource consuming part anyway?