TimMc wrote:Following a recent thread in the scripting forum, I submit the following FR:
I hope that a feature can be added to Celestia in the future that will allow for searching of deep-space objects loaded and for limited viewing of them (like the automag flag for stars).
This feature would only show DSO's that are near/bright enough to warrant displaying when moving the FOV. At present all DSO's in the FOV are rendered, even if they are so far in the distance as to effectively be point-like. As some DSO's can be very large textures on on very big 3D models, the consequence can be to slow down the frame-rate to a crawl. The alternative is to switch the "galaxies" renderflag off, which may not be desirable if, for example, one is viewing DSO's. So a variable rendering facility like automag for stars would be nice.
Tim Mc
When I coded the automag scheme, I thought of something like this already. Yet it is harder to quantify first of all, since the brightness (in magnitudes) of
extended objects is often not a relevant criterion for their actual visibility.
The automag scheme is based on (an idealized) equal distribution of many (pointlike) light sources of varying brightness.
The guiding principle was to keep their visible
density constant, when the field of view (FOV) is varied. So when e.g. the FOV gets smaller many stars drop out of the field. By increasing the mag limit, more stars will become visible, however, in the narrowed FoV. The automag scheme balances these to effects against each other.
An important prerequisite to make this work according to its design idea, is that the star data base is large enough, i.e. really comprises also many weak stars down to m=14-16, say. So the extended add-on db with 2 million stars is great for it!
In case of extended DSO's there are some major qualitative differences. Strong inhomogeneities (galaxy clusters...), the extendedness of DSO's and the request to have really
many such objects included are not easy to account for.
However, I agree, it might be well worth thinking more about extending the automag idea to them.
If there is interest, I would have much more to say here...
Bye Fridger
