bounce(Sprite *a, Sprite *b)
{
float x, y, n;
- float da, db;
+ float va, vb;
float ma, mb, mr;
// (x, y) is unit vector pointing from A's center to B's center.
n = sqrt(x*x + y*y); x /= n; y /= n;
// velocities along (x, y), or 0 if already moving away.
- da = max(x*a->dx + y*a->dy, 0);
- db = min(x*b->dx + y*b->dy, 0);
+ va = max(x*a->dx + y*a->dy, 0);
+ vb = min(x*b->dx + y*b->dy, 0);
// mass ratio
ma = sprite_mass(a); mb = sprite_mass(b);
if(ma && mb) mr = mb/ma; else mr = 1;
- a->dx += x*(db*mr - da); a->dy += y*(db*mr - da);
- b->dx += x*(da/mr - db); b->dy += y*(da/mr - db);
+ a->dx += x*(mb*vb - ma*va)/ma; a->dy += y*(mb*vb - ma*va)/ma;
+ b->dx += x*(ma*va - mb*vb)/mb; b->dy += y*(ma*va - mb*vb)/mb;
}