void ImplicitInterrogator::setImplicit(std::string s)
{
	_implicit = empty_p;
	ParticleSystem *psys = ps->particleSystem;
	if (psys) {
		Surfaces *surfs = psys->surfaces;
		if (surfs) {
			_implicit = dynamic_cast<Implicit *>(surfs->withName(s));
			if (!_implicit) _implicit = empty_p;
		}
	}
}