Hi Thorsten,
AFAIK, the Celestia textures are pretty much directly derived from the
Blue Marble textures available from NASA
http://earthobservatory.nasa.gov/Features/BlueMarble/
http://visibleearth.nasa.gov/view_cat.php?categoryID=1484
Clouds:
http://visibleearth.nasa.gov/view.php?id=57747
I think deriving directly from them would be most appropriate; Terms of
Use are:
http://visibleearth.nasa.gov/useterms.php
1) The imagery is free of licensing fees
2) NASA requires that they be provided a credit as the owners of the imagery
... which is GPL compatible as I read it.
Thank you very much for beginning to tackle this!
Regards,
Johannes
On 16.03.2012 11:12, Renk Thorsten wrote:
In the last two days, I've managed to implement a scheme for orbital terrain
rendering which I had cooked up a while ago.
Compared with what vitos had in mind (a complete overhaul of the rendering
engine) this is really low-tech and lives within the limitations of the
current engine - just a textured sphere of 58 km diameter in the scene which
is constantly repositioned using simple ray-optics to give the right
impression and has a dedicated shader to never fog it and work around the
high altitude light problem (see below). The results using Celestia Level 3
texturing are quite compelling, although there are a few quirks left:
http://www.flightgear.org/forums/viewtopic.php?f=6t=15754
It took me 7 hours to get it to this point, less than 100 lines of Nasal,
some cut-past with the shaders - most of the time I spent stitching and
converting textures. Right now it is really dumb - one can go to even higher
resolution texturing by investing some smartness and introducing texture
management (currently Earth is effectively covered by 4096x8192, the cloud
layer adds the same amount). At low altitudes, it transits automatically to
default (not very seamless at this point...).
I would very much like to fly this with something other than the ufo -
unfortunately there are a few problems in the way:
1) The weird 'zones' at high altitude:
- below 300.000 ft, rendering looks normal, default terrain is basically
gone, but Earthview shows something
- from 300.000 ft to 500.000 ft: grey zone - the sky above turns fog grey.
Lauri explained to me that this is because we leave the skydome behind, so
there is really nothing left to paint on
- from 500.000 ft to 800.000 ft: red zone - everything turns now red. No idea
what this is.
- above 800.000 ft: dark zone: the light largely disappears apart from a deep
red hue and the background finally becomes the deep black of space as it
should be (I re-defined the light in the planet shader not to pay attention
to this, but the ufo itself is of course affected) . The visible disk of the
sun turns red.
Can these effects be tracked and fixed to give a consistent background black
and reasonable light?
2) The high altitude FDM problem:
Our only spacecraft (Vostok) makes just 150 km altitude, apparently to
prevent it from running into a region where the FDM breaks down. This isn't
nearly high enough to see nice orbit scenes without pushing gigabytes of
textures at the problem. I have not really understood the reason in detail,
but can the JSBSim people comment on that? Is it possible to get JSBSim to
fly up to 3000 km, or to otherwise address this problem?
3) Other Spacecraft:
We currently have the X-15 (reaches barely 100 km and is in fact better with
the default rendering engine), SpaceShip-1 (doesn't really fly, the rocket
engine lacks the power to get anywhere, is also just a modern X-15), the
Vostok (see above) and a Space Shuttle FDM.
Given the Space Shuttle FDM and the discussion of Space Shuttle SRBs in the
JSBSim model, it may just a wild stab in the dark, but does Jon have a
complete flight-worthy Space Shuttle FDM somewhere?
It's one of the things I would like to fly at some point. Now there is
something to see in orbit, so maybe that makes it more interesting for 3d
modellers and FDM developers to work on some more spacecraft? It's a bit of a
chicken and egg problem, modelling orbital rendering isn't really so exciting
without a way to fly there, modelling spacecraft isn't interesting without
rendering - but I think there is progress. Right now, with Earthview FG looks
better than Orbiter out of the box, although Orbiter has the support for
hires texturing. But when you descend, Flightgear has a whole planet modelled
in really high detail to offer :-)
Well, I hope this is a more reasonable approach than what Vitos had in mind.
All things said, I would like to see Flightgear go into space a bit more. No
need to switch to Windows then :-)
I have tried to contact the Celestia people about the licensing of the
textures - as soon as I know, I can make this available in some form to
anyone interested.
Cheers,
* Thorsten
