[Bf-cycles] Remove old Sky Model

[Stefan Werner]

Hi,

I know we’re getting into a philosophical debate here, but in my opinion, what was good clean code two years ago, will still be good clean code ten years from now if you don’t touch it - code doesn’t rust. For what it’s worth, should the Preetham model get removed, most likely we will keep it in alive in our Poser version of the Cycles source code, so that we don’t take away features from the user. If it’s better for Blender and its users to remove the Preetham model, we’ll be able to work with it.

-Stefan

> On 04.04.2016, at 18:11, Thomas Dinges <blender at dingto.org> wrote:
> 
> Hi,
> 
> The benefit is "get rid of legacy algorithms". If we would get a more realistic Glass shader (at the same performance level), no one would complain that the render looks different (aka backwards compat breakage). We kinda have the same argument here. Even in the Hosek paper, it directly compares with the Preetham model.
> 
> I can add it back for 2.7x (to keep compatibility, as Ton suggested), but later I really like to remove it. I don't want to end up with a Blender Internal 2.0, which has gazillions of buttons and options after 5 years.