[Stellarium-pubdevel] Multi-resolution images

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

Dear all,
I commited yesterday the first working multi-resolution image loading code
in SkyImageTile.hpp/cpp. It allows to load/unload dynamically a tree of
tiles of a large image. The tiles are described in JSON files (I also coded
a Qt JSON parser), for example this one:
http://www.eso.org/~fchereau/N874/N874_00_00_x64.json, which is the first
tile of a full DSS plate (7 levels). All data can be accessed from the
network or from local disk or both combined. The textures are loaded in
threads.

This new code will be very useful for several things:
 1- Provide a full sky survey loaded dynamically. I have at work a full sky
version of the DSS which looks even nicer as the one from googlemap, and I
would like to provide it. Most of the technical problems have now been
solved. The only, but biggest problem is to find servers to host the 300 Gb
of data.. If you have an idea, let me know..
 2- Convert the current nebula and constellation art textures to this
format. For the constellation art, we'll have to create one JSON file per
texture, each having at least 2 levels, and maybe a 3rd level with higher
resolution textures stored online. For the nebula, we can simply create a
single large JSON file and load it at start-up (and maybe use the current
milky way texture as the level 0 tile). We can also have high resolution
levels for some nebulas. This also means that when this is done, we can
completely separate the nebula textures management from the nebula manager
itself. The latter should only manage nebula catalogs. This should also have
a positive impact on loading speed and video memory usage.
 3- Try to use the same class also for having high resolution landscapes.
The JSON file contains a list of vertex in real space, and a list of
matching 2d vertex in texture space, so it should work even for complex
meshes.
 4- Try to use the same class for planets maps. We could then zoom on high
resolution moon map :))

Appart from those already exciting new features, the fact that any user can
provide his own set of astro images, just by giving a URL will hopefully
increase a lot the users contributions!

Fabien