First i need to define what halfspace for me is: a set of two lines one vertical and one horizontal [ they ofc are defined (A1, B1, C1) and (A2, B2, C2)] and a point at which those lines intersect)
The available halfspace is always behind these two lines.
But i need somehow to find areas where this set of halfspaces define (it can be a rect or just an halfspace with a intersection point - i meant that i cant define infinity (well actually i could because i anyway cut a space to some xy dimension so nothing that exceeds those values wont exist ok so from now one i need only to find rectangles that are defined by these halfspaces (the best would be all points.
See image below i am trying to find blue rects.
Hopefully one will understand what in trying to do if not tell me ill try to describe that more naturally
