sphere.py 文件源码

def uv_to_st(cls, u):
        if cls.PROJECTION == cls.LINEAR_PROJECTION:
            return 0.5 * (u + 1)
        elif cls.PROJECTION == cls.TAN_PROJECTION:
            return (2 * (1.0 / math.pi)) * (math.atan(u) * math.pi / 4.0)
        elif cls.PROJECTION == cls.QUADRATIC_PROJECTION:
            if u >= 0:
                return 0.5 * math.sqrt(1 + 3 * u)
            else:
                return 1 - 0.5 * math.sqrt(1 - 3 * u)
        else:
            raise ValueError('unknown projection type')