Celestia Forums

Has anyone made a nebula add-on for the Milky Way before? This one is only 2k and is a little crude if you get too close, but I think I can use it for illustration purposes. It is of course largely fictional, but it does show the outer (Cygnus) arm, the Perseus arm, the Orion arm (at the centre of Selden's useful graticule), the Sagittarius arm, the Norma arm and the Scutum-Crux arm.

I like it.

It is an impressive result for a simple trick: I think I see a real galaxy (which NGC number?) with a simple barred spiral model superimposed to create the texture. The bar looks to be at about the right angle. It's interesting to see the brightest stars showing from the stars catalogue still do not seem to follow any spiral arms.

It is a 2D texture though, so I guess in the galactic plane it's not very visible? What if you used the simple barred spiral pattern to 'displacement map' the NGC galaxy texture into two meshes, one for +Z and one for -Z, say about 1,000 light years high and low at the sun's location, 5,000 light years over the core. Wouldn't that make the galaxy a bit 3D surround, even when you're 'inside' it?

Have I explained myself adequately?

Spiff.

That is right; making it was a little more complex, involving cutting and pasting various bits from M51 onto a diagram of our galaxy; but it is flat, and I can't really imagine any way of giving it a good 3d effect.

It looks quite good as you rotate it until you get near the plane of the galaxy
but then it disappears.

I'll put it up on the new Orion's Arm Motherlode page
http://www.celestiamotherlode.net/catal ... onsarm.php
and then anyone can play with it to see if they can make it more 3d.

The OA Motherlode page is looking a bit bare, but it has one big download now- about 100 megs;
this represents the core OA universe.
Any more worlds I make will be issues as addons to this large download.
Of course other member of the OA community may well post their own addons on this page too;
it is open to any contributions.

it doesn't even show up on my computer....sure i have everything enabled, i check the file.....but still nothing....can ya tell me what's gion on?

It doesn't work for me either, for some reason; I'll have to take advice.

Which "it" are you referring to?
The Web page in your browser,
the download Zip file on your system
or the Addon in Celestia?

I'm in the process of downloading it now.
So far so good. (I'm using Firefox.)

[edit]
*grump*

the download hung after fetching about 2/3 of the file. Trying again...
and it hung almost immediately.

I'll try later in the day from work.
[/edit]

I am grateful for your attention, Selden; I had hoped to fix it myself, but no such luck.
To achieve transparency, I used your Graticule addon as a starting point- that is why the texture is labelled graticule-green.png.

Anim8tor doesn't allow me to use transparent textures as far as I know.

The add-on was apparently working when I first downloaded it (but perhaps I had a good copy hiding on my system somewhere, which made me think the add-on worked okay.)

Perhaps I was a little over ambitious here...

eburacum45 wrote:Anim8tor doesn't allow me to use transparent textures as far as I know.

I think it may recognize GIF images with Alpha channels, although, of course, Celestia does not. At any rate, you can use a binary editor to change the file name in the 3DS file. (I usually use emacs, which usually damages the file so it can't be read by a 3D modelling program, although Celestia doesn't care.)

The add-on was apparently working when I first downloaded it (but perhaps I had a good copy hiding on my system somewhere, which made me think the add-on worked okay.)

Perhaps I was a little over ambitious here...

I don't think so.

One problem is that it uses a 2K surface texture image. The size limit is 1K for older graphics cards as well as for Microsoft's software OpenGL implementation. Modern ATI cards (9200 or better) have a 2K limit although modern Nvidia cards (4100 or better) have a 4K limit. I'd suggest including both 1K and 2K images.

It's working for me at work, where I use an Nvidia FX 5100.

Another gotcha is that you have to remember to enable Nebula drawing (type a caret) and possibly to disable Galaxy drawing to avoid visual confusion. Enabling only Galaxy drawing causes Celestia to use its entirely different internal model for the Milky Way.

Another potential problem: you have it centered at the Sun. I'd suggest centering it at the center of the Milky Way using the same RA, Dec and Distance values as are in \data\deepsky.dsc
You'll have to change the image so it's centered on the model, though, which actually would allow you to improve its apparent resolution. Currently it's about the equivalent of a 1K image.

I hope these suggestions help a little.

That looks nice. They think that this galaxy looks like M 109.

http://en.wikipedia.org/wiki/Spiral_Galaxy_M109

selden wrote:

eburacum45 wrote:Anim8tor doesn't allow me to use transparent textures as far as I know.

I think it may recognize GIF images with Alpha channels, although, of course, Celestia does not. At any rate, you can use a binary editor to change the file name in the 3DS file. (I usually use emacs, which usually damages the file so it can't be read by a 3D modelling program, although Celestia doesn't care.)

For windows I use Wordpad, you just have to make sure to save it without formatting.

- Buggs

A couple of months ago, I made a change to the code to have a new special "MW" galaxy type for the Milky Way.
I believe our mother galaxy deserves a special type (instead of the ugly thing in the standard package).
I made a *.pts model for it right from the same "artist view".
In fact I have several models with various levels of brightness).
Some shots (notice the new "MW" type).

Model alone:


Texture alone:


Combined (look how both fit together):


Maybe Vincent will want to integrate it into his next release
If so, I will post the patches.

Now that's COOL! I especially like the first screenshot.

Boux wrote:Maybe Vincent will want to integrate it into his next release

Your Milky Way .pts is really nice looking Boux, but it is based on a artist view. On the other hand, the default .pts model for SBc Galaxy type is a little bit too 'simplistic' for our galaxy which belongs to a more specific type called SBbc.

Our galaxy surely deserves a more specific model, and your patch is really interesting because it gives the possibility to customize the MW model without changing the other SBc Galaxies.

Fridger was talking about adding more specific galaxy types a few monthes ago. If he still plans to do it in a near future, maybe we would better wait for his release since we would be sure then it will be scientifically accurate...
If not, I think we could integrate your patch and provide your .pts model if its orientation is scientifically accurate, or any other model that would be more accurate to the last scientific observations...

Vincent wrote:

Boux wrote:Maybe Vincent will want to integrate it into his next release

Your Milky Way .pts is really nice looking Boux, but it is based on a artist view. On the other hand, the default .pts model for SBc Galaxy type is a little bit too 'simplistic' for our galaxy which belongs to a more specific type called SBbc.

Our galaxy surely deserves a more specific model, and your patch is really interesting because it gives the possibility to customize the MW model without changing the other SBc Galaxies.

Fridger was talking about adding more specific galaxy types a few monthes ago. If he still plans to do it in a near future, maybe we would better wait for his release since we would be sure then it will be scientifically accurate...
If not, I think we could integrate your patch and provide your .pts model if its orientation is scientifically accurate, or any other model that would be more accurate to the last scientific observations...

"but it is based on a artist view"
Lol, are there any Milky Way representations other than artist's views?
As far as I know, no space probe has been taking shots of the Milky Way from outside of it until now.
There are several variants of speculative representations circulating over the net.
"orientation is scientifically accurate"
It is /perfectly/ aligned on the existing SBc type. If my model's orientation is wrong, then Celestia's model is wrong.
The patch's purpose is to define an additional galaxy type. Whether this new type calls this (my) particular model or any other one is up to the user. Just rename any *.pts to MW.pts.

Boux wrote:Lol, are there any Milky Way representations other than artist's views?

Of course, there are no direct representation of our galaxy from outside of it. But the MW was first assimilated to a SBc type galaxy, and we have already observed some SBc galaxies from outside. That's why the Sbc type in Celestia was the most accurate.

So here's the point : which representation is the most accurate ?
1- The Sbc type that we know is way too simplicist but that really exists
2- Any interpretation (like the artist view from the Nasa website you've posted) of the latest scientific observations, that we know are speculative, but that might be closer to the real aspect of our galaxy.

I personnaly vote for the 2nd one

That's why I suggested to wait for any sign of an improvement concerning the galaxy types in the next official release... If it can't be done in a near future, I think a lot of users would be really happy to customize the Milky Way (via your patch) according to the latest scientific hypothesis...

i really like the way the model's done...can ya create a download link for it?

This morning I was bored, so I made a new Milky Way model:

Boux,

Here's a link to a recent post in which Fridger /officially / confirmed the Milky Way as a SBbc type galaxy : http://www.celestiaproject.net/forum/viewtopic.php?p=65642

From that post and...
- since Celestia 1.4.1 is going to be released very soon...
- since it is mostly an important maintenance release with no improvement concerning the galaxy rendering...

I think we can provide an experimental 1.4.1 version with your patch and your .pts model (not the last one you've posted ). We can also go further and replace the MW type (not scientifically accurate ) with the SBbc type :



As you can see, I managed to change the code ( ) to integrate the new SBbc type. But as I'm not a programmer, could you please provide your patch to confirm my changes ?

Could you also check the luminosity of your .pts model. The (old ?) one I used seems to be lower in luminosity than the other galaxy models. Here's a Sbc galaxy (from nearly the same distance) to compare with (light gain set to 0 % in both shots):