+ vector<Attachment>::const_iterator i = attachments.begin();
+ vector<Attachment>::const_iterator j = old->attachments.begin();
+ while(i!=attachments.end() || j!=old->attachments.end())
+ {
+ if(i!=attachments.end() && (j==old->attachments.end() || i->unit<=j->unit))
+ {
+ i->texture->bind_to(i->unit);
+ if(j!=old->attachments.end() && j->unit==i->unit)
+ ++j;
+ ++i;
+ }
+ else
+ {
+ Texture::unbind_from(j->unit);
+ ++j;
+ }
+ }
+ }
+ else
+ {
+ for(vector<Attachment>::const_iterator i=attachments.begin(); i!=attachments.end(); ++i)
+ i->texture->bind_to(i->unit);