[Stellarium-pubdevel] Stars/nebulas

[F. C. <fab...@go...>]

Hi,
I've just commited some more changes about star/nebula rendering. This
time I changed quite a bit of things, so I would like you to give me
your impressions.
What I did is mostly:
 - Use a special increasing brightness factor relative to zoom level
so tha the nebula look the way we expect them when zooming-in
 - Computed proper surface brightness for the messier nebulas textures.
 - I couldn't use the same formula for both point sources and extended
ones although I tried hard. This means that the special factor doesn't
applies to point sources.
 - I tried to desaturate the colors of the stars by multiplying the
RGB component by some factors until it looked more like the DSS survey
RGB color plates. It also improved the way the twinkling renders.
 - I added a non linearity in the last stage of star rendering to
allow for discriminating better bright stars with respect to small
ones.

I am not yet totally satisfied with everything but the comparison
nebula/stars rendering looks much more consistent.
I know that some of the things I did are purely empirical, but at the
end it looks closer to what people see, and also closer to the DSS
plates when zoomed in.

The next step again is to adjust adaptation when zooming in on a very
bright object like a planet.

Fabien