Smoke trails for objects in Celestia?

[medusa]

Hi folks,

some time ago I had the idea that a nice "eye candy" for my Impactors addon would be to have some smoke trails when the meteoroides run through planetary atmospheres at their last few seconds.
Just posted a thought to Sitting Duck's new A4 missile addon that it could be nice for it, too.

So, how could it be done? A first "scratch" theoretical approach was to create a transparent 3D object which follows the meteoroide / missile quite close-up and to apply a semi-transparent texture to it. I didn't try yet. Could it work this way?

~Diane.

[Vincent]

Hi Diane,

ElChristou already tried to add some smoke trails for his Shuttle model, but he gave up because there was a problem about the emissive part of the trail...

You'll find more information there :

http://celestiaproject.net/forum/viewtopic.php ... ecf597df48

http://celestiaproject.net/forum/viewtopic.php ... ecf597df48

[Boux]

Hi Medusa,
A quick and dirty way to add a trail to an object is to stick a 'tail' model to the main object with a 'bright' texture mapped on it.
Now, the Celestia engine has limitations in this area and I did not succeed yet in making the trail emissive.
However, if there is some light source that lights the object, a very rough approximation can be achieved.
As an example of my trials, I stuck cone models (borrowed from some add-on) to the drives of the Kerchan ship as seen on the picture.
http://jmmi.club.fr/celestia/warp_1024.png
BTW, as a sidenote, your experiments with home-made lasers are fascinating.
I mean you have got incredible manual skills (besides your scientific knowledge) to be able to build these experiments from a lot of recycled material

[medusa]

The emissive part of the trail doesn't be such a problem for me. Meteoroides don't exhaust some flame (at least not in a rough approximation).
The shiny part of a meteoroide or bolide is the bow shock. It could be handled seperately if there arise problems. The smoke trail just *is* smoke in this case, molten material blown away from the body's surface which recrystalized forming black smoke.

A bow shock from a mathematical point of view is a rotation hyperboloid. Any 3ds objects of such stuff in here...?

BTW, I didn't understand how the trails you hinted were attached to the models. I would like to have it as seperate objects. (The smoke shouldn't pop off when the meteoroide body impacts surface.)

@vincent: thanx for the hint....

@ElChristou: COOL shuttle boosters!!!

@Boux: a wonderful ship you've got there, captain... I guess I'll download and "borrow" the trail models from it, too.
About the lasers, my manual skills aren't *that* great. The photos don't show there's hardly a staight angle anywhere. It all fits together just one single way...

~Diane.

[selden]

Diane,

Celestia now does a reasonably good, but not always correct, job of displaying models that overlap. Unfortunately, most of the rendering problems are related to translucent surface textures.

One way to simplify the design is to have several models of exactly the same size but with different sections visible. E.g. one model of the body (with an invisible tail) and one of the tail (with an invisible body). Their SSC then can list each of the different models, all of them following exactly the same trajectory, perhaps with different Beginning and Ending times.

[buggs_moran]

Does anyone know how they do the smoke/contrails in Orbiter. I think it is OpenGL/Open source as well...

[selden]

Nope, sorry.
Although it's free, Orbiter is closed source and uses DirectX, not OpenGL.

[medusa]

As far as I see, Orbiter does some particle trace methods to have exhaust trails or at least a reentry wake. (Browsed the site for a better model of the S-IVB stage to have a possible improvement of the J002E3 addon)
I remember from my work in aerospace research that particle trace methods aren't that simple but give very realistic results for high-speed flight in thin atmospheres. Guess that's simply outside the scope of Celestia - which is ASTRONOMY not spaceflight.

~Diane.