def visible(self, points, radius):
        """Determine whether this sphere is visible in frustum

        frustum -- Frustum object holding the clipping planes
            for the view
        matrix -- a matrix which transforms the local
            coordinates to the (world-space) coordinate
            system in which the frustum is defined.

        This version of the method uses a pure-python loop
        to do the actual culling once the points are
        multiplied by the matrix. (i.e. it does not use the
        frustcullaccel C extension module)
        """

        distances = numpy.sum(self.planes[numpy.newaxis, :, :] * points[:, numpy.newaxis, :], -1)
        return ~numpy.any(distances < -radius, -1)
Determine whether this sphere is visible in frustum

        frustum -- Frustum object holding the clipping planes
            for the view
        matrix -- a matrix which transforms the local
            coordinates to the (world-space) coordinate
            system in which the frustum is defined.

        This version of the method uses a pure-python loop
        to do the actual culling once the points are
        multiplied by the matrix. (i.e. it does not use the
        frustcullaccel C extension module)
        
frustum.py