def cylinder(cls, **kwargs):
        """ Returns a cylinder.
            
            Kwargs:
                start (list): Start of cylinder, default [0, -1, 0].
                
                end (list): End of cylinder, default [0, 1, 0].
                
                radius (float): Radius of cylinder, default 1.0.
                
                slices (int): Number of slices, default 16.
        """
        s = kwargs.get('start', Vector(0.0, -1.0, 0.0))
        e = kwargs.get('end', Vector(0.0, 1.0, 0.0))
        if isinstance(s, list):
            s = Vector(*s)
        if isinstance(e, list):
            e = Vector(*e)
        r = kwargs.get('radius', 1.0)
        slices = kwargs.get('slices', 16)
        ray = e.minus(s)

        axisZ = ray.unit()
        isY = (math.fabs(axisZ.y) > 0.5)
        axisX = Vector(float(isY), float(not isY), 0).cross(axisZ).unit()
        axisY = axisX.cross(axisZ).unit()
        start = Vertex(s, axisZ.negated())
        end = Vertex(e, axisZ.unit())
        polygons = []
        
        def point(stack, angle, normalBlend):
            out = axisX.times(math.cos(angle)).plus(
                axisY.times(math.sin(angle)))
            pos = s.plus(ray.times(stack)).plus(out.times(r))
            normal = out.times(1.0 - math.fabs(normalBlend)).plus(
                axisZ.times(normalBlend))
            return Vertex(pos, normal)
            
        dt = math.pi * 2.0 / float(slices)
        for i in range(0, slices):
            t0 = i * dt
            i1 = (i + 1) % slices
            t1 = i1 * dt
            polygons.append(Polygon([start.clone(), 
                                     point(0., t0, -1.), 
                                     point(0., t1, -1.)]))
            polygons.append(Polygon([point(0., t1, 0.), 
                                     point(0., t0, 0.),
                                     point(1., t0, 0.), 
                                     point(1., t1, 0.)]))
            polygons.append(Polygon([end.clone(), 
                                     point(1., t1, 1.), 
                                     point(1., t0, 1.)]))
        
        return CSG.fromPolygons(polygons)
Returns a cylinder.
            
            Kwargs:
                start (list): Start of cylinder, default [0, -1, 0].
                
                end (list): End of cylinder, default [0, 1, 0].
                
                radius (float): Radius of cylinder, default 1.0.
                
                slices (int): Number of slices, default 16.