(Use in turbowarp with hq pen enabled) draw line segments via the mouse, the white circle thingy snaps to the nearest vertex so that it's easier to not make gaps. Press space to build the tree. the green areas represent "solid" spaces whereas the red areas are "empty", the blue lines are supposed to be portals. The white lines are normals of the lines, make sure they point inward to the shape if you want the portalizer to work correctly i wanted to do PVS with this but school + other stuff made it so i didnt rlly have enough time. Perhaps someone else could add it thanks @littlebunny06 for answering all my bsp related questions
