Celestia Forums

A catalog of 73 planetary nebulae is now available for Celestia v1.3.

http://www.lns.cornell.edu/~seb/celestia/catalogs.html#3.7.3

Positions and InfoURLs are provided, but no dramatic pictures: just wispy grey ghosts of shells.

If you want to build up the images so theyr're more nearly visible, you can put multiple copies of the catalog (with different names, of course) in your /extras/ directory. Celestia will add the images together, eventually bringing them up to visibility.

I used the "roughsphere.cms" mesh. All they need now are some appropriate translucent textures. I can almost hear Chris groaning from here

It is indeed an idea to use the roughsphere.cms, but it doesn't seem to work with a texture in this case.
But it works with a 3DS mesh with a texture file. The difficulty is to have the proper rendering as seen from the solar system. I tried to make a couple (M31,M32,M110). Each time you have to give the correct orientation to the mesh. The Axis and Angle features that I've seen in the dsc files doesn't seem to work with the Mesh. I don't know if this is a bug or not! I wish we could use them.

Calculus wrote:It is indeed an idea to use the roughsphere.cms, but it doesn't seem to work with a texture in this case.
But it works with a 3DS mesh with a texture file. The difficulty is to have the proper rendering as seen from the solar system. I tried to make a couple (M31,M32,M110). Each time you have to give the correct orientation to the mesh. The Axis and Angle features that I've seen in the dsc files doesn't seem to work with the Mesh. I don't know if this is a bug or not! I wish we could use them.

If it's not working, it's a bug . . . It's critical to be able to manipulate the orientation of deep sky objects. I'll look into the problem.

--Chris

Paul,

The .DSC files aren't fully general (yet).

The "Texture" directive is not yet implemented, for example. I've been bugging Chris about that

Although "Axis" and "Angle" work for galaxies and are supposed to work for the other DSC entries, it could be that they don't yet. I suspect it would be useful if you could post a couple of screen shots and/or URLs illustrating the problem.

selden wrote:Paul,

The .DSC files aren't fully general (yet).

The "Texture" directive is not yet implemented, for example. I've been bugging Chris about that ;)

Although "Axis" and "Angle" work for galaxies and are supposed to work for the other DSC entries, it could be that they don't yet. I suspect it would be useful if you could post a couple of screen shots and/or URLs illustrating the problem.

Here is my DSC file:
Nebula "M31"
{
Mesh "M31____1.3ds"
RA 0.712
Dec 41.27
Distance 2.9e6
Radius 75000
Axis [ 0 0 1 ]
Angle 90
}

If I use Galaxy instead of Nebula, it doesn't work. (I have the default galaxy display).
The line Axis and Angle don't work. I have the same image with or without these lines (even if I change the angle or the axis values):
http://ennui.shatters.net/gallery/view_photo.php?set_albumName=Calculus&id=M31_M32_M110

I have also noticed, like Grant a while ago (but this is the first time I mess with meshes), that Celestia doesn't apply the texture files the same way other software do. I had to mirror my galaxies textures to have them correctly displayed.

Last, when I turn around the M31 galaxy, even though I changed the distance values of M32 and M110, M32 is always in front of M31 and M110. Even when I look from behind! Maybe it has to do with the distance limitation in Celestia.

Theres another problem when using modeled galaxies...When your inside them so to speak they will appear to dissappear due to the fact the inside is not rendered...unless you create a duplicate mesh and flip the surface to the inner part of the original mesh then attach them as one mesh...then apply the texture...Similar to the procedure I used with Eta Carinae...

Also currently when approaching models in celestia it seems they cut out in the center when getting to close...They may dissapear completely when entering them even with the inverted mesh surface added to the original due to some limitation in rendering...not quite sure whats going on there...however this cutting effect does happen with the NGC1999 mesh when its approached slightly too close....0.5 ly away your fine...Again Ive not enough data to go on to say whats going on here...May simply be the camera passing through the mesh is all...

Hey Calculus,
why is your M31 colored and mine not? Is this because of your own mesh file, or do i have a too old graphics card (TNT1)?

FaLLeN_SOuL,

It's because he's designed his own M31 using his own 3ds mesh and specified it bo be a Nebula. (Gee. Just like the original discoverers of them )

Rassilon wrote:Theres another problem when using modeled galaxies...When your inside them so to speak they will appear to dissappear due to the fact the inside is not rendered...unless you create a duplicate mesh and flip the surface to the inner part of the original mesh then attach them as one mesh...then apply the texture...Similar to the procedure I used with Eta Carinae...

Galaxies rendered as meshes will never look quite right from the inside. That was a big part of the motivation for the fuzzy blobs style of rendering--galaxies look sort of correct whether you're inside them or viewing them from a distance.

Also currently when approaching models in celestia it seems they cut out in the center when getting to close...They may dissapear completely when entering them even with the inverted mesh surface added to the original due to some limitation in rendering...not quite sure whats going on there...however this cutting effect does happen with the NGC1999 mesh when its approached slightly too close....0.5 ly away your fine...Again Ive not enough data to go on to say whats going on here...May simply be the camera passing through the mesh is all...

Yes, it's just the camera passing through the mesh. Or more precisely, the model intersecting the front clipping plane. I may be able to alleviate this effect somewhat.

I did find and fix the nebula orientation bug so that setting values for axis and angle will actually rotate the model.

--Chris

Calculus,
How do these galaxies look from say Earth orbit. Are they well defined or do they remain just blobs until you get closer?

Don. Edwards wrote:Calculus,
How do these galaxies look from say Earth orbit. Are they well defined or do they remain just blobs until you get closer?

M31 is a very big galaxy, so you can see it from earth and it looks the same as the image I posted but smaller. There is no blobs at all. The blobs era is finished. However, to my opinion, the M31 I made is much too bright and colorful.

i only get yellow circles in my program, i guess i need something else...

Ok,
So when do we all get to play with it. I mean Calculus' Andromeda Galaxy system.????????

Redfish wrote:i only get yellow circles in my program, i guess i need something else...

If you're referring to the planetary nebulae catalogs that I created, it sounds like you loaded the one which substitutes a lower case "o" for the names. At the moment, there are no images of planetary nebulae available for use in Celestia. Someone needs to develop them. The catalogs that I created will display very dim, ghostly, grey, bumpy spheres on some graphics cards. I can just barely see them when using my Nvidia Ti4200 at home, but I can't see them at all on an ATI Rage card at work.