cylinder_gen.py

def make_cylinder():
    FACETS = 12
    DFACETS = FACETS * 2
    RADIUS = 0.5
    HEIGHT = 1
    HALF_STEP = math.pi / FACETS
    TRIG_STEP = HALF_STEP * 2

    geom = Geometry()

    geom.add_normal(Vector3(0, -1, 0))
    geom.add_normal(Vector3(0, 1, 0))
    geom.add_vertex(Vector3(0, 0, 0))
    geom.add_vertex(Vector3(0, HEIGHT, 0))

    for i in xrange(FACETS):
        norm_x = math.cos(TRIG_STEP*i + HALF_STEP) * RADIUS
        norm_z = math.sin(TRIG_STEP*i + HALF_STEP) * RADIUS
        geom.add_normal(Vector3(norm_x, 0, norm_z))
        norm_i = i + 2

        x = math.cos(TRIG_STEP*i) * RADIUS
        z = math.sin(TRIG_STEP*i) * RADIUS
        geom.add_vertex(Vector3(x, 0, z))
        geom.add_vertex(Vector3(x, HEIGHT, z))

        vert_gen = lambda n: ((i * 2 + n) % DFACETS) + 2

        # Counter clockwise winding
        geom.add_face(Face(vert_gen(0), vert_gen(2), vert_gen(1), norm_i, norm_i, norm_i))
        geom.add_face(Face(vert_gen(1), vert_gen(2), vert_gen(3), norm_i, norm_i, norm_i))

        # Top and bottom lid
        geom.add_face(Face(0, vert_gen(2), vert_gen(0), 0, 0, 0))
        geom.add_face(Face(1, vert_gen(1), vert_gen(3), 1, 1, 1))

    return geom