Hi, I tried searching the internet for an answer, but didn't find anything, so 
I'll ask here.

One problem with normal collision detection I'm sure we're all aware of is the 
problem that objects moving too fast can pass through other objects without a 
collision happening. I'm experiencing this problem with a scrolling shooter I'm 
working on because both bullets and enemies move pretty fast, one enemy is very 
small, and the frame rate is usually somewhat low (maybe 30 FPS) on the machine 
I'm targeting.

Now, obviously, I intend to make other changes which will help, e.g. making 
these tiny enemies bigger, but I'd like to tackle the problem directly. There 
are two ways I can think of: The first way, which I easily could implement and 
would be most effective, is to move the bullets in steps and do collision 
detection each step. I have done something like this in a previous game and it 
worked well, but it seems like overkill in this game (the bullet subrect is 
only 5x5 pixels) and it isn't perfect anyway.

The second way, which I would prefer, is to detect collision with a line from 
the bullet's new position to the bullet's previous position. I've seen this 
discussed on the Game Maker Community. The problem with this is I have no idea 
of how this could be done in a remotely efficient manner. The only method I can 
think of is to check every individual pixel one at a time, which is obviously 
not a good idea. Bullets can move diagonally, so just checking the x or y 
position won't work.

So, in a nutshell, my question is: how could I do "line collision" detection 
like this in a relatively efficient way?

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