colour.phenomena.sky_luminance_distribution_CIE2003#

colour.phenomena.sky_luminance_distribution_CIE2003(sky_type: int, Z: ArrayLike, alpha: ArrayLike, Z_s: ArrayLike, alpha_s: ArrayLike) → NDArrayFloat[source]#

Compute the relative sky luminance \(L_{\alpha} / L_z\) for the given CIE Standard General Sky type.

The relative luminance at any point is the ratio of the luminance of an arbitrary sky element to the zenith luminance \(L_z\):

\(L_{\alpha} / L_z = f(\chi) \cdot \varphi(Z) / (f(Z_s) \cdot \varphi(0))\)

Parameters:

  • sky_type (int) – CIE Standard General Sky type (1-15).

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

  • alpha (ArrayLike) – Azimuth angle \(\alpha\) of the sky element in radians (clockwise from north).

  • Z_s (ArrayLike) – Zenith angle \(Z_s\) of the sun in radians.

  • alpha_s (ArrayLike) – Azimuth angle \(\alpha_s\) of the sun in radians (clockwise from north).

Returns:

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

Return type:

numpy.ndarray

Raises:

ValueError – If sky_type is not in range [1, 15].

References

[]

Examples

>>> sky_luminance_distribution_CIE2003(
...     1, np.radians(45), np.radians(180), np.radians(30), np.radians(0)
... )
np.float64(0.8325846...)
>>> sky_luminance_distribution_CIE2003(
...     12, np.radians(45), np.radians(180), np.radians(30), np.radians(0)
... )
np.float64(0.4544524...)