Differential D13361 Diff 45286 intern/sky/include/sky_model.h

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intern/sky/include/sky_model.h

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solarElevation		solarElevation
);		);

Note that starting with version 1.3, there is also a second initialisation		Note that starting with version 1.3, there is also a second initialisation
function which generates skydome states for different solar emission spectra		function which generates skydome states for different solar emission spectra
and solar radii: 'arhosekskymodelstate_alienworld_alloc_init()'.		and solar radii: 'arhosekskymodelstate_alienworld_alloc_init()'.

See the notes about the "Alien World" functionality provided further down for a		See the notes about the "Alien World" functionality provided further down for a
discussion of the usefulness and limits of that second initalisation function.		discussion of the usefulness and limits of that second initialisation function.
Sky model states that have been initialized with either function behave in a		Sky model states that have been initialized with either function behave in a
completely identical fashion during use and cleanup.		completely identical fashion during use and cleanup.

Using the model to generate skydome samples		Using the model to generate skydome samples
-------------------------------------------		-------------------------------------------

Generating a skydome radiance spectrum "skydome_result" for a given location		Generating a skydome radiance spectrum "skydome_result" for a given location
on the skydome determined via the angles theta and gamma works as follows:		on the skydome determined via the angles theta and gamma works as follows:
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arhosekskymodelstate_alienworld_alloc_init() function		arhosekskymodelstate_alienworld_alloc_init() function
-----------------------------------------------------		-----------------------------------------------------

Initializes an ArHosekSkyModelState struct for an "alien world" setting		Initializes an ArHosekSkyModelState struct for an "alien world" setting
with a sun of a surface temperature given in 'kelvin'. The parameter		with a sun of a surface temperature given in 'kelvin'. The parameter
'solar_intensity' controls the overall brightness of the sky, relative		'solar_intensity' controls the overall brightness of the sky, relative
to the solar irradiance on Earth. A value of 1.0 yields a sky dome that		to the solar irradiance on Earth. A value of 1.0 yields a sky dome that
is, on average over the wavelenghts covered in the model (!), as bright		is, on average over the wavelengths covered in the model (!), as bright
as the terrestrial sky in radiometric terms.		as the terrestrial sky in radiometric terms.

Which means that the solar radius has to be adjusted, since the		Which means that the solar radius has to be adjusted, since the
emissivity of a solar surface with a given temperature is more or less		emissivity of a solar surface with a given temperature is more or less
fixed. So hotter suns have to be smaller to be equally bright as the		fixed. So hotter suns have to be smaller to be equally bright as the
terrestrial sun, while cooler suns have to be larger. Note that there are		terrestrial sun, while cooler suns have to be larger. Note that there are
limits to the validity of the luminance patterns of the underlying model:		limits to the validity of the luminance patterns of the underlying model:
see the discussion above for more on this. In particular, an alien sun with		see the discussion above for more on this. In particular, an alien sun with
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