n = sqrt(x*x + y*y); x /= n; y /= n;
// velocities along (x, y), or 0 if already moving away.
- va = max(x*a->dx + y*a->dy, 0);
- vb = min(x*b->dx + y*b->dy, 0);
+ va = x*a->dx + y*a->dy;
+ vb = x*b->dx + y*b->dy;
+ if(vb-va > 0) return;
ma = sprite_mass(a); mb = sprite_mass(b);
vc = (va*ma + vb*mb) / (ma+mb);