me? i thought it was simple enough, but maybe not...say somewhere in the object struct or class you have a variable like
float CollisionRadius;
then assign it a value so that the distance between the center of the object and the farthest edge is contained in the circle, like
Object1.CollisionRadius = 5;
do that for all objects...ie
Object2.CollisionRadius = 5;
then compare their distance
using the distance formula (i think this is it)
Dist = sqrt((Object1.x - Object2.x)^2 + (Object1.y - Object2.y)^2)
and add the radii:
Sum = Object1.CollisionRadius + Object2.CollisionRadius;
Then if Dist < Sum, a collision has occured, else they haven't hit each other
<(o)>
Edited by - aDasTRa on 4/26/00 11:29:52 PM
Collision Detection
aDastra: you''re correct, but what you described is about what Whatever already described in his 2nd post.
Daricon, that''s correct, X and Y are just the separation distances between the centers of the two circles. Also, I thought of a simple alternative to the code I gave earlier: If you detect a collision, you could actually just switch the two circles'' velocities. Here''s the code:
if(collisionDetected){
FLOAT tempX = circle1.velX;
FLOAT tempY = circle1.velY;
circle1.velX = circle2.velX;
circle1.velY = circle2.velY;
circle2.velX = tempX;
circle2.velY = tempY;
}
Note the following limitations: your collision will be 100% elastic, which looks particularly retarded in head-on collisions. Also, my previous code could be modified easily to simulate circles of different masses, whereas this "pseudo-physics" solution can only treat them as equal masses.
Daricon, that''s correct, X and Y are just the separation distances between the centers of the two circles. Also, I thought of a simple alternative to the code I gave earlier: If you detect a collision, you could actually just switch the two circles'' velocities. Here''s the code:
if(collisionDetected){
FLOAT tempX = circle1.velX;
FLOAT tempY = circle1.velY;
circle1.velX = circle2.velX;
circle1.velY = circle2.velY;
circle2.velX = tempX;
circle2.velY = tempY;
}
Note the following limitations: your collision will be 100% elastic, which looks particularly retarded in head-on collisions. Also, my previous code could be modified easily to simulate circles of different masses, whereas this "pseudo-physics" solution can only treat them as equal masses.
Author
Eric:
I tried that new code. It seems to work pretty well in some cases, but it gets funky in others. I think the problem has to do with this part:
Let's say that circle1 is on the left and has a positive X velocity and circle 2 is one the right and has a neagtive one. This is assuming that +Xvelocity moves the circle to the right and -Xvelocity to the left. Forget about Y velocity for a second. It works in this case and they both bounce off each other (a little slower) in opposite directions. The funky stuff starts if circle2 in left with a +Xvel and circle1 is on the right with a -Xvel. They sort of eat into each other and don't bounce off right.
How did you get past this? I haven't done it yet, but I guess I will see where the circles are before the collision and then have some if statements to decide whether I do
or
and the same for the other three lines.
Anyway, thanks Eric. You've been most helpful.
::Daricn::
Edited by - Daricon on 4/27/00 8:35:50 PM
I tried that new code. It seems to work pretty well in some cases, but it gets funky in others. I think the problem has to do with this part:
circle1.velX += unitSepX * collisionVelocity;circle1.velY += unitSepY * collisionVelocity; circle2.velX -= unitSepX * collisionVelocity;circle2.velY -= unitSepY * collisionVelocity; Let's say that circle1 is on the left and has a positive X velocity and circle 2 is one the right and has a neagtive one. This is assuming that +Xvelocity moves the circle to the right and -Xvelocity to the left. Forget about Y velocity for a second. It works in this case and they both bounce off each other (a little slower) in opposite directions. The funky stuff starts if circle2 in left with a +Xvel and circle1 is on the right with a -Xvel. They sort of eat into each other and don't bounce off right.
How did you get past this? I haven't done it yet, but I guess I will see where the circles are before the collision and then have some if statements to decide whether I do
circle1.velX += unitSepX * collisionVelocity; or
circle1.velX -= unitSepX * collisionVelocity; and the same for the other three lines.
Anyway, thanks Eric. You've been most helpful.
::Daricn::
Edited by - Daricon on 4/27/00 8:35:50 PM
This topic is closed to new replies.
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