Flash MX 2004 Games : Art to ActionScript

Flash MX 2004 Games
if a and b are both vectors containing two components x and y. The function ‘dotproduct’ is
designed to return this value.
function dotproduct(x1, y1, x2, y2){
return (x1 * x2 + y1 * y2);
}
But the dot product of two vectors has another definition:
a·b =|a||b| cos θ
This means that the dot product is the magnitude of one vector times the magnitude of the other
times the cosine of the angle between them. If each has magnitude 1, they are unit vectors, and
then the dot product is the cosine of the angle between the two vectors. If this value is less than
or equal to zero then we can calculate the new velocities for the objects involved in the collision.
If the value is positive then the collision has occurred with the opposite side of the object, that
is the objects totally overlap; if we allow such a collision then the effect will be to bounce in the
opposite direction to the desired result.
1 function collision(name){
2 //Get the normal of the collision
3 cnx = (_x + vecx) - (eval(name)._x + eval(name).vecx);
4 cny = (_y + vecy) - (eval(name)._y + eval(name).vecy);
5 //Get magnitude of normal and normalise
6 mag = Math.sqrt(cnx * cnx + cny * cny);
7 cnx /= mag;
8 cny /= mag;
9 //Set masses for collision objects
10 ma = 20;
11 mb = 20;
12 //Coefficient of restitution value,
13 //how much force is lost in collision
14 e = -(1 + 0.8);
15 //Components of player’s velocity are already known
16 vax = vecx;
17 vay = vecy;
18 //Calculate components of player b velocity
19 if (eval(name).speed!=0){
20 vbx = eval(name).vecx;
21 vby = eval(name).vecy;
22 }else{
23 vbx = 0;
24 vby = 0;
25 }
26 //Calculate relative velocity
298