Hi, at the moment I am programming my collision detection. I wonder what possibilities there are to detect a collision between a line (Points: P1, P2) and a Box (Points: B1-B8) Right now I got a algorithum that is only good on high frame rates because I test if P1 is INSIDE the box or P2 is inside the Box. Although i think i need a old Position value to eleminate the "jump" of my laser - I mean if the Framerate drop below 40 (on older PC''s) I have the effect that the enemy is never hit because the (fast) laser that is infront of the enemy jumps behind the enemy and there is no collision detected. So I thought of a "oldPos" info in the laser (this is P2) so I can determine if a laser''s travled way made a collision with a enemy. due to the enemy (low against the laser - problably ration: 1:5) speed it is not nessesary to determine the time acpect (I think) - if it is needed (if a ship where hit even if it was not realy at a point i could have been hit I will see what I need to do then) So how to determine if a Line hits a Box at any Point of the Line. - One way I think of is a for loop but thist is to CPU hungry I think. (how that people are able to understand my situstion and questions) thank you

is your box an aabb or an obb ?

if you are using obb, you will probably need an algo to detect collisions between 2 obb. Then you can just see your line as an obb with 2 dimensions reduced to 0 . So you just have to apply your obb-algo to this stange obb. ( and to make it faster, dont test null-axis. )

and well, if it''s an aabb you can still do the same thing (but there is probably something faster)

Tang

AABB is unrotated and OBB is rotation with the object right?

OK I will try to find something about this two in google.

thank you.

But the main thing how to determine if a line goes though this is not answered with this - or am i missing something out?


and what about bouncing speheres - they would be the fastest way to determine, aren't they?

But as I said the main issue that I need to clear out is how to determine that the enemy is hit if the framerate is to low to have enough tests/secound and the laser jumps from one point to another without comming to close to an enemy.



[edited by - Dominik_78 on December 6, 2002 1:47:06 AM]

>AABB is unrotated and OBB is rotation with the object right?
yes, that''s it

>But the main thing how to determine if a line goes though this >is not answered with this - or am i missing something out?

the colliding algo of obb (or aabb , or spheres) can be easily extended to check wheter 2 boxes with a linear velocity collide during a duration t. So it can answer your problem.

>and what about bouncing speheres - they would be the fastest >way to determine, aren''t they?

well, I suppose it depends of your application. a single test between spheres is certanly faster, but you may need more tests to get the same accuracy.


Tang

>AABB is unrotated and OBB is rotation with the object right?
yes, that''s it

>But the main thing how to determine if a line goes though this >is not answered with this - or am i missing something out?

the colliding algo of obb (or aabb , or spheres) can be easily extended to check wheter 2 boxes with a linear velocity collide during a duration t. So it can answer your problem.

>and what about bouncing speheres - they would be the fastest >way to determine, aren''t they?

well, I suppose it depends of your application. a single test between spheres is certanly faster, but you may need more tests to get the same accuracy.


Tang