+function doLinesIntersect(x1,y1, x2,y2, x3,y3, x4,y4)
+ local intersect = false
+
+ if x1 == x2 and x3 == x4
+ or y1 == y2 and y3 == y4
+ then
+ -- if lines are parallel, no intersection!
+ elseif x1 == x2 and y3 == y4 then
+ intersect = (
+ x3 <= x1 and x1 <= x4
+ or
+ x4 <= x1 and x1 <= x3
+ ) and (
+ y1 <= y3 and y3 <= y2
+ or
+ y2 <= y3 and y3 <= y1
+ )
+ elseif x3 == x4 and y1 == y2 then
+ intersect = (
+ x1 <= x3 and x3 <= x2
+ or
+ x2 <= x3 and x3 <= x1
+ ) and (
+ y3 <= y1 and y1 <= y4
+ or
+ y4 <= y1 and y1 <= y3
+ )
+ else
+ print('foo')
+ end
+
+ if intersect then
+ scene.intersection = {
+ a = {x1,y1, x2,y2},
+ b = {x3,y3, x4,y4},
+ }
+ end
+
+ return intersect
+end
+
+function doesLineIntersectPlayerPaths(path, x1,y1, x2,y2)
+ local cache = {}
+ cache.a = {}
+ cache.b = {}
+ -- for every line in path,
+ -- check intersection with player line
+ for k,v in pairs(path) do
+ if #cache.a == 2 then
+ if #cache.b == 2 then
+ if doLinesIntersect(x1,y1, x2,y2, cache.a[1],cache.a[2], cache.b[1],cache.b[2]) then
+ return true
+ end
+ end
+ cache.b = cache.a
+ cache.a = {}
+ end
+ table.insert(cache.a,v)
+ end
+ return false
+end
+
+-- love collision handler
+function collision(player)
+ print('Player '..tostring(player)..' crashed!')
+ scene.paused = true
+ --love.event.quit()
+end
+love.handlers.collision = collision
+
+function scene:handleCollisions()
+ -- calculate the last line for each player from current position
+ -- check if line intersects any other path line
+ -- if so, raise collision event for player
+ for _,player in pairs(self.players) do
+ local x1 = player.path[#player.path-1]
+ local y1 = player.path[#player.path]
+ local x2 = player.position.x
+ local y2 = player.position.y
+
+ -- check intersection against each existing path
+ for _,player2 in pairs(self.players) do
+ if doesLineIntersectPlayerPaths(player2.path, x1, y1, x2, y2) then
+ love.event.push('collision', player)
+ end
+ end
+ end
+end
+