Improved Graticules for Celestia

[selden]

I've made a set of graticules to help show the universe in perspective.

Here they're drawn in the ecliptic of the solar system.


Various colors of graticules are included, although the pattern is the same on them all.

http://www.lns.cornell.edu/~seb/celestia/graticule.zip (800KB)

See its enclosed readme for details. A Web page will be available eventually.

These graticules are rather crude, since they're surface texture images on flat 3DS models. Someday, if some form of vector graphics becomes available in Celestia, much better versions would be possible.

[selden]

v2 of the graticules are now available which fix most of the problems that were in v1. Graticules with units of parsecs have been added.

http://www.lns.cornell.edu/~seb/celestia/graticules-v2.zip (800KB, 25jan04)

See http://www.lns.cornell.edu/~seb/celestia/graticules.html for details.

[fsgregs]

Selden:

Thank you for these. They clearly took some work and effort. For someone like me who uses Celestia in teaching, they will be invaluable, particularly since I have not yet met one school kid who truly understands the scale of the universe before taking my course. I can think of several ways I will be using them.

One question.

I would like to use them in my Educational Activities, but only at certain times. Given that these are models, they will display as an add-on as soon as you put them in the extras folder. Is there a way to turn them "off" when I don't need them, without closing Celestia? For example, could I put a "beginning" command in the ssc file so that they only turn on if I go to the year 4000 CE or something and turn off when the year changes to 4001?

Regards,

Frank

[selden]

Frank,

You're quite welcome to use them, of course.

Unfortunately, I don't know of any way to turn a Nebula off and on once it's been loaded. There are many features associated with SSC files and their textures that don't work in DSC files. It'd be really nice if they did.

For example, Beginning and Ending directives don't work in DSC files. Being able to select alternate textures or resolutions would be another major improvement. So would virtual textures, even if they could only be used on spheres.

One thing that is possible is to use a model that's visible only from one side. For example, you would not see the grid if you looked "down" from "above" the solar system (from the "northern" side), but it would be visible if you looked up from below (from the southern side).

Do you think that would be an acceptable solution?

Added somewhat later:

I've created http://www.lns.cornell.edu/~seb/celestia/graticules-1sided-v2.zip

See http://www.lns.cornell.edu/~seb/celestia/graticules.html for details.

[DaveMc]

Selden,

Thanks for making these! FWIW, on my system there appears to be a bug with both the "graticules-v2" and "graticules-1sided-v2" files. When stars are selected as "Fuzzy Points" they (the stars) become square pixels. If stars are viewed as "Points" everything seems OK. Not sure if this is an issue with the graticules or my system.

Thanks,
Dave

Gateway 1700cx
1.7GHz P4
80 GB Hard Drive (63 GB available)
512 MB RAM
ATI Radoen VE 7000 Video Card, 64 MB RAM
WIN ME
Celestia 1.3.1-1

[Bob Hegwood]

Mr. Ball,

I'm sorry, but I just HAVE to ask...

What the hell is a Graticule?

Take care, Bob

[selden]

Dave,

The "square stars" syndrome is a bug in Celestia that's tickled by having a transparent surface in a model. Chris is working on it.

Bob,

"Graticule" is just a fancy word that means "an alignment pattern."

[Bob Hegwood]

That's why I love this place, Selden...

Where *else* in the world would I have *ever* heard that terminology?

You sure are expanding my limited education here...

Thanks, Bob