for(vector<Tag>::const_iterator i=pass_order.begin(); i!=pass_order.end(); ++i)
render(*i);
for(vector<Effect *>::const_iterator i=effects.end(); i--!=effects.begin();)
for(vector<Tag>::const_iterator i=pass_order.begin(); i!=pass_order.end(); ++i)
render(*i);
for(vector<Effect *>::const_iterator i=effects.end(); i--!=effects.begin();)