/** * Line-through-box intersection algorithm. * * There are a few possibilities, with B() meaning * "on blocking side", I() meaning "intersecting" * and P() meaning "on pass-through side": * * | * (1) [] [] <| = B(prev), B(current) * | * * | * (2) [] [<|] = B(prev), B(current) and I(current) and P(current) * | * * | * (3) [] <| [] = B(prev), P(current) * | * * | * (4) [<|] [] = B(prev) and I(prev) and P(prev), P(current) * | * * * | * (5) <| [] [] = P(prev), P(current) * | * * By computing the dot product for the eight corners of the two bounding * boxes, we can determine which of these situations we are in. Only in * (2) and (3) should we signal an intersection occuring. While (4) might * look like another case in which this should happen, we assume that * because the "previous" state is boundary overlapping, it was permitted * earlier (for instance, it moved through the boundary in the allowed * direction, but then moved back before having fully passed the boundary). */ <textarea> </body> </html>