returns a list of frames from startframe to stopframe, in steps of framestepj
        warning: the list of points may include "None" elements 
        :param beginframe: first frame to include in list of points
        :param endframe: last frame to include in list of points
        :param framestep: framestep 
        :param birthframe: frame before which animation always returns None
        :param startframe: frame from which animation starts to evolve 
        :param stopframe: frame in which animation completed
        :param deathframe: frame in which animation starts returning None 
        :param filternone: automatically remove None entries
        :param noiseframe: for time varying noise, this represents the time for which the noise should be evaluated
        :return: list of tweened values

def curve_points(self, beginframe, endframe, framestep, birthframe, startframe, stopframe, deathframe,
                     filternone=True, noiseframe=None):
        """
        returns a list of frames from startframe to stopframe, in steps of framestepj
        warning: the list of points may include "None" elements 
        :param beginframe: first frame to include in list of points
        :param endframe: last frame to include in list of points
        :param framestep: framestep 
        :param birthframe: frame before which animation always returns None
        :param startframe: frame from which animation starts to evolve 
        :param stopframe: frame in which animation completed
        :param deathframe: frame in which animation starts returning None 
        :param filternone: automatically remove None entries
        :param noiseframe: for time varying noise, this represents the time for which the noise should be evaluated
        :return: list of tweened values
        """
        if endframe < beginframe and framestep > 0:
            assert False, "infinite loop: beginframe = {0}, endframe = {1}, framestep = {2}".format(beginframe,
                                                                                                    endframe, framestep)
        if endframe > beginframe and framestep < 0:
            assert False, "infinite loop: beginframe = {0}, endframe = {1}, framestep = {2}".format(beginframe,
                                                                                                    endframe, framestep)

        i = beginframe
        result = [self.make_frame(i, birthframe, startframe, stopframe, deathframe, noiseframe)]
        while i < endframe:
            i += framestep
            if i <= endframe:
                result.append(self.make_frame(i, birthframe, startframe, stopframe, deathframe, noiseframe))
        if filternone:
            return filter_none(result)
        else:
            return result