collision detection with circles

[blanius]

here's a little info on collision detection


You can go to Sampe movie and drag the balls to see example

you can get the movie source for that example at
source

Basically what I've done is to calculate the distance from ball 1 and ball 2 and if it is less than or equal to 24 then they have collided.

a=abs (element ("ball1").x - element ("ball2").x);
b=element ("ball1").y - element ("ball2").y;

dist= sqrt (a*a+b*b); 

[blanius]

Playing around further I came up with the following functions:

function distance(element1,element2){
    a=abs (element1.x - element2.x);
    b=element1.y - element2.y;
    return sqrt (a*a+b*b);
}

function collide(distance,width){
    return distance<=width
    } 

put those in your starting script then when you want to check for a hit do this

dist=root.distance(element ("ball1"),element ("ball2"));
hit=root.collide(dist,24); 

Or better yet let the function do all the work:

function C_collide(element1,element2)
    {
    //get width of both elements
    width1=(element1.getBounds().xMax-element1.getBounds().xMin)-5
    width2=(element2.getBounds().xMax-element2.getBounds().xMin)-5
    //get distance 
    a=element1.x - element2.x;
    b=element1.y - element2.y;
    dist= sqrt (a*a+b*b);
    //account for different sizes
    width=(width1/2)+(width2/2);
    //check distance and size
    
    //return t/f
    return dist<=width
    } 

not sure why I had to subtract 5 from the widths but I found I did.

then call this function like this:

hit=root.C_collide(element ("ball1"),element ("ball2")); 

Hope you find this useful!