Returns a list of Location4D objects

def boundary_interaction(self, **kwargs):
        """
            Returns a list of Location4D objects
        """
        particle = kwargs.pop('particle')
        starting = kwargs.pop('starting')
        ending = kwargs.pop('ending')

        # shoreline
        if self.useshore:
            intersection_point = self._shoreline.intersect(start_point=starting.point, end_point=ending.point)
            if intersection_point:
                # Set the intersection point.
                hitpoint = Location4D(point=intersection_point['point'], time=starting.time + (ending.time - starting.time))
                particle.location = hitpoint

                # This relies on the shoreline to put the particle in water and not on shore.
                resulting_point = self._shoreline.react(start_point=starting,
                                                        end_point=ending,
                                                        hit_point=hitpoint,
                                                        reverse_distance=self.reverse_distance,
                                                        feature=intersection_point['feature'],
                                                        distance=kwargs.get('distance'),
                                                        angle=kwargs.get('angle'),
                                                        azimuth=kwargs.get('azimuth'),
                                                        reverse_azimuth=kwargs.get('reverse_azimuth'))
                ending.latitude = resulting_point.latitude
                ending.longitude = resulting_point.longitude
                ending.depth = resulting_point.depth
                logger.debug("%s - hit the shoreline at %s.  Setting location to %s." % (particle.logstring(), hitpoint.logstring(),  ending.logstring()))

        # bathymetry
        if self.usebathy:
            if not particle.settled:
                bintersect = self._bathymetry.intersect(start_point=starting, end_point=ending)
                if bintersect:
                    pt = self._bathymetry.react(type='reverse', start_point=starting, end_point=ending)
                    logger.debug("%s - hit the bottom at %s.  Setting location to %s." % (particle.logstring(), ending.logstring(), pt.logstring()))
                    ending.latitude = pt.latitude
                    ending.longitude = pt.longitude
                    ending.depth = pt.depth

        # sea-surface
        if self.usesurface:
            if ending.depth > 0:
                logger.debug("%s - rose out of the water.  Setting depth to 0." % particle.logstring())
                ending.depth = 0

        particle.location = ending
        return