The getskytype function determines the CIE general standard sky type for a given luminance distribution of a Tregenza hemisphere. The function can operate in two different modes: The ‘tregenza’ mode (Tregenza 2004) where the whole hemisphere is consideredand and the ‘kobav’ mode (Kobav et al. 2012) which only considers certain parts of the hemisphere. The Tregenza method is more accurate for full data sets but the Kobav et al. method is better suited for incomplete data sets. Both determination methods are available as indipended functions and can be used directly.
See also: tregenzaskytype, kobavskytype
[sky,RMS] = getskytype(L,sunaz,sunel,mode,parameter)
Where:
| Parameter | Description |
sky | Returns the best fitting CIE standard general sky as in CIE S 011. |
RMS | Returns the Root Mean Square deviation from the best fitting CIE standard general sky. Both methods use different approaches, hence the RMS values are not comparable between the determination methods. In case of ‘kobav’ method the mean RMS from indicatrix and gradation determination is returned. |
L | Defines the Tregenza hemisphere luminance distribution. |
sunaz | Defines the sun azimuth angle \alpha_S. |
sunel | Defines the sun elevation angle \gamma_S. |
mode | Defines the determination mode: ’tregenza’ (default) uses the determination method described in Tregenza 2004. ’kobav’ uses the determination method described in Kobav et al. 2012. |
parameter | Both determination methods allow addidtional parameters: ‘tregenza’ method – ‘center’ (default) uses the patch center points for reference luminance determination. – ‘mean’ uses the mean of the patch corner points (interpolated) for reference luminance determination. ‘kobav’ method: – ‘cie’ (default) returns the CIE skytype according to the CIE table. Not all gradation and indicatrix group combinations result in a CIE skytype, resulting in NaN value.– ‘nearest’ returns the closest match to the CIE skytype table. |
Examples
Determine skytype at \alpha_S = 166\degree and \gamma_S = 33\degree with ‘tregenza’ method:
L = ciesky(12,166,33); [sky,RMS] = getskytype(L,166,33,'tregenza')
See also: ciesky
Result:
sky = 12 RMS = 0
Determine skytype at \alpha_S = 166\degree and \gamma_S = 33\degree with ‘tregenza’ and ‘mean’ method:
L = ciesky(12,166,33); [sky,RMS] = getskytype(L,166,33,'tregenza','mean')
See also: ciesky
Result:
sky = 12 RMS = 0.2285
Note: the differences to reference sky modell in terms of RMS are due to the different determination method ‘mean’.
Determine skytype at \alpha_S = 166\degree and \gamma_S = 33\degree with ‘kobav’ method:
L = ciesky(12,166,33); [sky,RMS] = getskytype(L,166,33,'kobav')
See also: ciesky
Result:
sky = 12 RMS = 0.019045
References