from idorudraw import beginTrianglesEntity, triangle

def avg(x, y):
    return (x+y)/2.0

# Do not use triangle strips: too short, consume too much entities
def quad(x0, y0, x1, y1, x2, y2, x3, y3):
    triangle(x0, y0, x1, y1, x3, y3)
    triangle(x1, y1, x2, y2, x3, y3)

def cell(x0, y0, x1, y1, x2, y2, x3, y3):
    x01 = avg(x0, x1); y01 = avg(y0, y1)
    x12 = avg(x1, x2); y12 = avg(y1, y2)
    return [x0, y0, x01, y0, x01, y12, x0, y12,
            x01, y0, x1, y0, x1, y12, x01, y12,
            x0, y12, x01, y12, x01, y2, x3, y2]

# TODO: simplify; several values are probably redundant
# The result? When setting n big enough the fractal is
# undistinguishable from a sierpinski triangle
def tile(x0 = -10, y0 = -10, x1 = 10, y1 = -10,
         x2 = 10, y2 = 10, x3 = -10, y3 = 10, n = 4):
    beginTrianglesEntity()
    s = cell(x0, y0, x1, y1, x2, y2, x3, y3)
    for i in range(1, n):
        r = s
        s = []
        # for j in range((cellinput.len/celloutput.len)**i)
        for j in range(3.0 ** i):
            s.extend(cell(r[j*8 + 0], r[j*8 + 1], r[j*8 + 2], r[j*8 + 3],
                          r[j*8 + 4], r[j*8 + 5], r[j*8 + 6], r[j*8 + 7]))
    for i in range(3.0**n):
        quad(s[i*8 + 0], s[i*8 + 1], s[i*8 + 2], s[i*8 + 3],
             s[i*8 + 4], s[i*8 + 5], s[i*8 + 6], s[i*8 + 7])