I need some ideas in order to finish algorithm. I'm randomly placing objects (bitmaps) on canvas without overlapping. Time needed to finish it is my problem. When I need to spawn for example 80% of canvas it takes to long. So i was thinking : I should make some change when the bitmaps take off 50 % of canvas. I want to tell algorithm that it should generate new locations (x,y) where it is free space. My question is : How to render new location (x,y) in place where is free space. In summary: Things I know : object location (x,y) 4 corners (x,y) of object object width, height canvas width, height Any suggestions?