colour.phenomena.sky_luminance_distribution_overcast_CIE2003#

colour.phenomena.sky_luminance_distribution_overcast_CIE2003(Z: ArrayLike) → NDArrayFloat[source]#

Compute the relative sky luminance \(L_{\alpha} / L_z\) for the CIE Traditional Overcast Sky (the 16th sky type).

\(L_{\alpha}(\gamma) / L_{zenith} = (1 + 2 \sin \gamma) / 3\)

where \(\gamma\) is the angle of elevation of the sky element above the horizon.

Parameters:

Z (ArrayLike) – Zenith angle \(Z\) of the sky element in radians.

Returns:

Relative sky luminance \(L_{\alpha} / L_z\).

Return type:

numpy.ndarray

References

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Examples

>>> sky_luminance_distribution_overcast_CIE2003(0)
np.float64(1.0)
>>> sky_luminance_distribution_overcast_CIE2003(
...     np.pi / 2
... )
np.float64(0.3333333...)