def world_pairs(self):
if self._recalc_world_pairs:
pairs = self._world_pairs = []
for (a1, a2, m) in self.pairs:
wm = B2D.b2WorldManifold()
wm.Initialize(m, a1.transform, a1.shape.radius,
a2.transform, a2.shape.radius)
pairs.append((a1, a2, wm))
self._recalc_world_pairs = False
return self._world_pairs
