thanks a lot for your answers ! They are definitely helpful.
I was not speaking specifically about skylight here even if topics are definitely connected. ;-)
I have been looking at some papers myself for the past few months and there are indeed different approaches/datasets :
Sebastien Hilaire has done a great presentation
, comparing different approaches (with LUTs, without...).
So we could say that skylights are indeed a complex topic which include many factors/parameters.
In my original question, I was actually more talking about light's temperatures, like an area light.
If we look at Arnold, Guerilla or Renderman,
you may find in the lights some temperature options.
If we look at the Renderman documentation :
We can read that at 15000 to 27000
kelvin temperature would be a clear blue poleward sky
. Except that it looks very red/purple...
I wish there would be a mention : blackbody values are not recommended for temperatures above 5500 for example. But if there is
no general agreement/consensus on a daylight data set, that would indeed make things hard to implement. ;-)
I don't know if any of this makes sense,