cube graphics in nodebox with hidden surface removal

cube_hsr1.py

"""
classes for vertex, rectangle
"""
class Vertex(object):
    def __init__(self, x, y, z):
        self.x = x
        self.y = y
        self.z = z

    def __add__(self, other):
        if isinstance(other, Vertex):
            x, y, z = other.x, other.y, other.z
        elif isinstance(other, tuple) or isinstance(other, list):
            x, y, z = other

        self.x += other.x
        self.y += other.y
        self.z += other.z

    def __mul__(self, n):
        self.x *= n
        self.y *= n
        self.z *= n
V = Vertex


class Polygon(object):
    def __init__(self, *args):
        if not args:
            self.verts = []
        else:
            self.verts = args

    def add_vertex(self, v):
        self.verts.append(v)

    def __getitem__(self, n):
        return self.verts[n]

    def __len__(self):
        return len(self.verts)

    def surface_normal(self):
        v0, v1, v2 = self.verts[0:3]
        return v1.x * (v2.y - v0.y) + v0.x * (v1.y - v2.y) + v2.x * (v0.y - v1.y)
R = Polygon


"""
main
"""
from math import sin, cos, pi

rad = pi / 180.0
L = 80

cube = [
    R(V(0, L, 0), V(L, L, 0), V(L, 0, 0), V(0, 0, 0)),
    R(V(L, L, 0), V(L, L, L), V(L, 0, L), V(L, 0, 0)),
    R(V(0, L, L), V(L, L, L), V(L, L, 0), V(0, L, 0)),
    R(V(0, L, L), V(0, L, 0), V(0, 0, 0), V(0, 0, L)),
    R(V(L, 0, L), V(0, 0, L), V(0, 0, 0), V(L, 0, 0)),
    R(V(L, L, L), V(0, L, L), V(0, 0, L), V(L, 0, L)),
]

size = (360, 360)
speed(60)


def setup():
    global a, b
    a, b = 0, rad * 0.3


def draw():
    global a, b
    a = (a + 0.02) % (2 * pi)
    b = (b + 0.01) % (2 * pi)
    
    translate(180, 180)
    fill(0.7, 0.7, 1)
    stroke(0, 0, 0)

    for r in cube:
        draw_rect(r, a, b)


def draw_rect(r, a, b):
    moved_rect = Polygon()

    for v in r:
        x =  v.x * cos(b) + v.z * sin(b)
        z = -v.x * sin(b) + v.z * cos(b)
        y =  v.y * cos(a) -   z * sin(a)
        moved_rect.add_vertex(V(x, y, z))

    if moved_rect.surface_normal() < 0:
        return

    for i, v in enumerate(moved_rect):
        if i == 0:
            beginpath(v.x, v.y)

        lineto(v.x, v.y)

        if i == (len(r) - 1):
            endpath()