sun_and_sky.py 文件源码

def cie_relative_luminance(sky_elevation, sky_azimuth=None, sun_elevation=None,
                           sun_azimuth=None, type='soc'):
    """ cie relative luminance of a sky element relative to the luminance
    at zenith

    angle in radians
    type is one of 'soc' (standard overcast sky), 'uoc' (uniform radiance)
    or 'clear_sky' (standard clear sky low turbidity)
    """

    if type == 'clear_sky' and (
                sun_elevation is None or sun_azimuth is None or sky_azimuth is None):
        raise ValueError, 'Clear sky requires sun position'

    if type == 'soc':
        return cie_luminance_gradation(sky_elevation, 4, -0.7)
    elif type == 'uoc':
        return cie_luminance_gradation(sky_elevation, 0, -1)
    elif type == 'clear_sky':
        return cie_luminance_gradation(sky_elevation, -1,
                                       -0.32) * cie_scattering_indicatrix(
            sun_azimuth, sun_elevation, sky_azimuth, sky_elevation, 10, -3,
            0.45)
    else:
        raise ValueError, 'Unknown sky type'