Celestia Forums

Does anybody know of a more realistic texture for comet tails?

I brought up the idea over a year ago about possibly skinning comets to look more realistic. It fell on deaf ears. So the answer is no. Chris was suppose to tweak the code to make them less blue as well, again nothing happened. This is one of the reasons why I just keep to making textures anymore. The early days of getting exciting new things into Celestia has past. Of course this is in no way says what Fridger has done with Galaxies isn't exciting. But any involvement from Chris these days is nearly nonexistent and it alienates the community as a whole.

Don.

Don. Edwards wrote:The early days of getting exciting new things into Celestia has past. Of course this is in no way says what Fridger has done with Galaxies isn't exciting. But any involvement from Chris these days is nearly nonexistent and it alienates the community as a whole.

Don.

I dunno, I'm just discovering celx scripting and there's potentially a lot of cool stuff to be done there. Plus you don't need to intimately know programming to do that, and it doesn't rely on anyone else being around to make it available - you can just put scripts on your own website or the motherlode.

But I guess from a visual perspective you're right - anything that requires changes to the rendering code seem to be stuck without Chris.

Plus, who says we couldn't delete the existing comets files and make our own tails?

buggs_moran wrote:Plus, who says we couldn't delete the existing comets files and make our own tails?

I don't think the tails are actually there as files to delete - they're in the rendering engine itself (I think? I can find models for the comet nuclei but not for any tails...)

Malenfant wrote:

buggs_moran wrote:Plus, who says we couldn't delete the existing comets files and make our own tails?

I don't think the tails are actually there as files to delete - they're in the rendering engine itself (I think? I can find models for the comet nuclei but not for any tails...)

Rendering engine be damned then. Turn off comet tails. Create a new tail mesh (this one was a 5 minute quickie just for proof of concept) Someone feel like taking on the modeling of a tail? I could spend some time on it in the future. Problem is the comet tail length changing over time and pointing away from stellar wind for ion tail and pointing away from pressure of star for dust tail...

buggs_moran wrote:Problem is the comet tail length changing over time and pointing away from stellar wind for ion tail and pointing away from pressure of star for dust tail...

That's why it might be better left to the rendering engine. It could potentially do the calculations for the direction and strength of the winds (roughly) to get the tails pointing in the right direction and at the right length. A model/mesh is fairly static.

I think right now it's best to think of the current comet tails as being 'schematic' rather than realistic.

hmmm... wouldn't it be possible to define the tail mesh as co-orbiting object (just copying the .ssc file from the comet you're trying to 'tail') and then set it's rotation period to match the comet's orbit period? If you could set [aphelion = tail pointing away] , then it would always point away from the sun. (I think so, but I'm almost sure it would work.)

* off to test it *

Here it is!
Always wanted to get rid of the horrible blue color:

Made some changes in the rendering source code.

Boux wrote:Here it is! Made some changes in the rendering source CODE

Hello Boux, could you please show a screenshot with less stars, please?
I'm very interested in your comet rendering.
Thank you.
Bye

Andrea

Sure, with nothing in the background:

RGB values are 0.3 0.3 0.3 to get a light greyish tint.

Boux wrote:Here it is!
Always wanted to get rid of the horrible blue color:

Made some changes in the rendering source code.

That's nice Boux. Its fine to get rid of the blue colour for the dust tail, but what about the ion tail, wouldn't you have blue in that? It obviously wouldn't be too striking, like the photographs or the originally rendered tails. It would be awesome if we could get the tail motion close to show students how the tails move independantly of one another... I guess I'll have to take a crash course in coding.

Yep, another light blue ionic tail, if possible at a small angle with the dust tail.
Should not be as proeminent as the existing one though.
Have to look at the code again

Boux wrote:Sure, with nothing in the background:
RGB values are 0.3 0.3 0.3 to get a light greyish tint.

Thanks a lot, Boux.
If I can add a little cent on the matter, I looked with telescopes at comets a lot of times, so I can say that the ionic tail is surely bluish, but the dust tail color is grey with a visible light bluish hint. Nothing like the original Celestia comet tail, but perhaps something halfway between your grey and Celestia's blue color.
I think that the blue-grey distinction is more evident on images than by eye, IMHO, and we are looking at Celestia with our eyes, not on a photograph, so ...
The double tail improvement is very interesting, as was discussed some tima ago, but now it seems that perhaps something can be done on the matter.
We are with you, Boux.
Bye

Andrea

Boux wrote:Sure, with nothing in the background:

RGB values are 0.3 0.3 0.3 to get a light greyish tint.

Nice! That looks more like a real comet tail anyway...

Would we be able to see the coma of the comet too? Or is that only visible in long exposure photos?

Question: are comet tails really THAT wide? I think they should be made a bit thinner, IMO.

New rendering with light blue-greyish tint with more transparency:



For those interested in playing with the code, in render.ccp:

lines
5785 {
5786 float shade = abs(viewDir * v.normal * v.brightness);
5787 glColor4f(0.2f, 0.2f, 0.3f, shade/1.5);
5788 glVertex(v.point);
5789 }

This looks MUCH better !

Fridger, could you add this in the FT1.2 ?

Cham wrote:This looks MUCH better !

Fridger, could you add this in the FT1.2 ?

Probably, since I have been suffering too, from these solid blue comet "pipes" in the past...

Certainly worth looking into it, since the changes are very trivial yet effective...

Bye Fridger

Here is comet Halley flying "towards Andromeda" in FT1.2



Bye Fridger