I’ve got a tile based map (see http://67.18.194.226/kev/grav2/grav2pg.jnlp). I have a non tile shaped ship colliding with the tiles. While I can happily tell when the ship has collided with a tile (using java.awt.geom.Areas), I now want to know which side of the tile was collided with (and hence the normal) to work out the bounce correctly.
Now, I’ve tried a few bits and pieces but all are horribly hacky…
Anyone got any ideas how to do this?
Kev
I was struggling with something like this a while ago, about the most general solution is to test all the line segments of one object against all the line segments of the other. That’ll give you a few segments that intersect, and if you’re lucky one of them will be a tile edge. If you’re unlucky you’ll get two tile edges when you bump into a corner. If you’re really unlucky you’ll get three edges when you totally swarm over an edge.
You could try seperating all the cases, but that could be tricky. A more mathematical way would the method of separating axies, which gives you a separation plane and penetration distance. Google should have quite a bit on it.
If you’re sure one will always be static (like with tiles) and all your tiles are the same shape then you can probably simplifiy things quite a lot. For a start you should be able to use your velocity to trim down the possible edges to one or two (can’t bump into an edge you’re moving away from 
).
And thats thats 
Velocity trimming plus a bit of jiggery pokery has sorted it. I have 5 different tile shapes and it all seems to work happily.
Thanks,
Kev