You could use the point of intersection between two lines.
One line is the bullet trajectory.
The other line is the target trajectory.
You have to take into account the time of the intersection too.
If the intersection falls inside the target at the right time for both
projectile and target then it is a hit.
Paul Bourke gives a simple explanation with C code examples at:
http://paulbourke.net/geometry/lineline2d/
That's for 2D. The 3D solution would be more complex, but not too much.
It could be simplified by making bullets travel instantaneously if
distance is negligible. In fact if that's the case there may be an even
simpler way of solving whether a line intersects a volume.
Cheers,
- Miriam
Julian Marchant wrote:
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?
--
If you don't have any failures then you're not trying hard enough.
- Dr. Charles Elachi, director of NASA's Jet Propulsion Laboratory
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Website: http://miriam-english.org
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http://miriam-e.livejournal.com
