On Tue, Sep 1, 2009 at 9:31 AM, Fridger Schrempp <fridger.schrempp@desy.de> wrote:
Chris,

welcome back!

After spending so much time on a workable method to render LARGE numbers of
DSOs automatically by computer, I am not at all "hot" to replace these
precisely calculated shapes by rough markers with wrong inclination...

Yet, what could be a sensible approach, is to use such elliptical markers
(indicating roughly  the locations, sizes and inclinations of DSOs), WHILE the
actual DSO rendering is still /invisible/ (for reasons of magnitude or size)!
A crucial constraint should then be that upon zooming-in, the outlines of
galaxies/globulars/nebulae will be /blended/ with and finallly substituted by
the actual, rendered DSO images. After all, there is no reason whatsoever to
step back to mere outlines ;-). In any case, I want to avoid an option where
my  DSO images can be replaced by markers...

The situation would be almost no different than it is now, where one can highlight the position of galaxies and other DSOs with markers whether or not DSOs are enabled.  The only difference is that all ellipsoid outline marker type would be available to better approximate galaxy shapes. I'm not proposing that we implement new marker style right away--there's much important work to be done now.

The only thing that would be done immediately is to remove the automatic markers for open clusters and nebulae from both 1.6.1 and the trunk. It's a bit of a regression for 1.6.1. In the trunk, we could add an option to the DSO browser to use markers with distance-based sizing, giving the same functionality as the automatic markers. Sound OK?

--Chris


Fridger

Chris Laurel wrote:
> I'm back from a weekend away in the North Cascades...
>
> I added the DSO symbols because it's useful to be able to see the
> locations of these objects, and they typically have no other visible
> representation in Celestia. Only a few nebulae are available in add-ons,
> and the stars of most open clusters aren't visible at a great distance.
> I think that they'd also be useful for galaxies and globulars, but I
> agree with Fridger that it's important to show the projected shape of
> galaxy ellipsoids, and to account for the effect of perspective when
> calculating marker sizes.
>
> It may not be necessary to have a built-in feature to show DSO symbols.
> It could be done via standard markers, which can be set to use 'distance
> based sizing' in order to show the apparent extent of DSOs. We could
> eventually add a new marker type 'ellipsoid' to show projected outlines
> of the galaxies. A user could either use the deep sky browser to mark
> DSOs or write a script to do the same thing. Using markers instead of
> built-in code offers a few advantages:
>
> - No need for yet another boolean render flag
> - Less code
> - More flexibility - user can choose the symbol and color for DSO markers
>
> So what I propose is:
> - Eliminate the code to draw DSO symbols
> - Augment the deep sky browser with some UI for specifying
> distance-based markers
> - In the future, add an ellipsoid marker type that's appropriate for
> showing approximate galaxy extents
>
> --Chris
>
>
> On Mon, Aug 31, 2009 at 2:48 AM, Fridger Schrempp
> <fridger.schrempp@desy.de <mailto:fridger.schrempp@desy.de>> wrote:
>
>     vincent wrote:
>
>         Fridger wrote:
>
>
>
>             I am confused: DSOs are generally "deep sky objects",
>             including galaxies and
>             globulars. Are you saying that you made a patch that can
>             display only the
>             borders of galaxies, if the normal display of the latter is
>             disabled? What is
>             precisely the border of galaxies in your code??? Or are
>             galaxies and
>             globulars excluded from all this (which I would strongly
>             argue for!)?
>
>
>
>         Fridger,
>
>         The code for drawing these "DSO borders" was implemented by Chris
>         quite a while ago. My patch only adds a *switch* for the display
>         of these "DSO borders", which could be defined as markers that are
>         displayed simultaneously with DSO labels and that indicate the DSO
>         size. There has been a discussion on the subject on the shatters
>         forum:
>         http://www.shatters.net/forum/viewtopic.php?f=3&t=14034
>         <http://www.shatters.net/forum/viewtopic.php?f=3&t=14034>
>
>         For some reason, these markers are currently drawn neither for
>         galaxies
>         nor for globulars. But this could be fixed with one single line
>         of code
>         for each...
>
>         @+
>         Vincent
>
>
>
>     Vincent,
>
>     really, I have a number of objections here. I suppose we should
>     first discuss the need for such code for DSO borders when Chris is back.
>
>     Certainly in case of galaxy clusters with many galaxies and labels
>     being visible at once, such additional markers are useless and will
>     destroy the nice realistic view. Since most galaxies appear as
>     strongly /inclined/  circular disks, the respective borders should
>     also be inclined. I suppose that up to now these borders are derived
>     "naively" in relation to the selection cursor marks, the code for
>     which is also relatively "un-mature" with respect to galaxies and
>     globulars, as I discussed recently with Chris already.
>
>     The borders of globulars are badly defined, whence such code also
>     makes little sense.
>
>     If desired I can easily strengthen these arguments against such
>     naive borders also physics-wise...
>
>     For reasons of GUI "transparency", we should avoid additional
>     switches that are not really necessary!
>
>     Fridger
>
>
>
>             vincent wrote:
>
>
>                 The following change adds a new render flag for DSO
>                 borders so that they
>                 can be displayed separately from DSO labels.
>                 http://vincent.giangiulio.perso.sfr.fr/celestia/dev/DSO_borders.patch
>
>                 For simplicity, I opted for one single render flag for
>                 all DSO's --
>
>
>             actually,
>
>
>                 for nebulae and open clusters, since borders are drawn
>                 neither for galaxies
>                 nor for globulars...
>
>                 The patch also adds the corresponding checkbox to the
>                 View Option dialog
>                 on the Windows GUI:
>                 http://vincent.giangiulio.perso.sfr.fr/celestia/dev/viewoptions.jpg
>
>                 @+
>                 Vincent
>
>
>                 Selon Selden E Ball Jr <seb1@cornell.edu
>                 <mailto:seb1@cornell.edu>>:
>
>
>
>                     Please don't forget that several additions should be
>                     made to
>                     the View Options menu for v1.6.1 which haven't
>                     happened yet.
>
>                     1. Add "Plane of Ecliptic" to the Grids section plus
>                     add code to
>                     turn off and on the red Ecliptic line. (The line is
>                     drawn when Celestia
>                     is installed for the very first time. It's one of
>                     the saved parameters,
>                     so people tend to forget about it once it has been
>                     turned off using
>                     a script.)
>
>                     2. Add checkboxes and code so that "DSO Borders" can
>                     be drawn separately
>                     from DSO Labels.
>
>                     There have been several complaints about both of these.
>
>                     s.
>
>
>
>
>
>
>
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