Perfect equatorial orbit?

[thepyratecaptain]

Hello, I'm kinda stumped, I am mixing starships in my universe, and I am wondering, how do I make a ship orbit perfectly around another object? I have tried tweaking the numbers, but no luck. Here's the gist of my delima, I have a dry dock with the excelsior in it, and I am trying to get the eagle one to orbit it correctly. Help?????

[selden]

It depends on what you mean by "orbit correctly".

The simplest orbit specification would be something like

Code: Select all

"spaceship" "star/planet/station"
{  Radius 0.25 # units are kilomenters
    Mesh "spaceship.3ds"
    EllipticalOrbit {
      Period 1  # units are days
      SemiMajorAxis 2  # units are kilometers
    }
}


This causes the 500 meter long spaceship to circle the station's equator once per day at a distance of 2 km.

[thepyratecaptain]

I think I see where my orbit correctly mistake is, but ok, the eagle one starship is the vessel, and earth is the planet, the two work well as orbits, go. But the perspective of the eagle is weird, I.e. Nose pointed up, instead of parallel to the direction of orbit. Same for the millennium falcon, and I think defiant. I just can't seem to get them to line up as if flying around the planets equator with the noses pointing in the direction they are going. Kinda silly, I know, but I enjoy this proggy a lot.

Can ya help?

[thepyratecaptain]

Ok I think I know what's going wrong, in the 3d model, the x y z axis might not be set correctly, example, the defiant always loads nose down. I think it's y axis is back, the x is top, and the z is front. Lemme guess, there's nothing I can do about it right?

[Fenerit]

If the nose and the tail of the vessel lies upon the X axis, try to add the directive "Orientation [90 1 0 0]" (without quotes) into the .SSC.

Edit Later:
Can you rotate the model with a 3D program?

[thepyratecaptain]

Hmmm I have tried that orientation command line, I don't think the nose lies directly on the x axis, and that be the problem, I have a cheap 3d viewer that does allow me to rotate and examine the models, but it always reverts to the incorrect alignment, gah! Frustrating, most of the federation/Klingon ships are correctly aligned, with the defiant being the exception, it looks funny in the space dock, nose down, lol. That's what I wish I could change, will be looking today on line for a way to rotate the world axis in the models to align them along the x axis, or perhaps one of you could do it and upload or email it to me?

Luvyandluiz@gmail.com

Thanks.

[thepyratecaptain]

ok well i got the defiant to behave, but that darn eagle one just wont. right now im using mercury as a vantage point, i have an image of the issue, will try to link it here.



"Eagle 1" "Sol/mercury"
{
Class "spacecraft"
InfoURL "http://www.space1999.net/~moonbase99/"
Mesh "eagle1999.3ds"
Radius 0.03
RotationOffset 240
Orientation [90 .99 -1.99 -.75]

CustomOrbit "Bird of Prey 0.12 "
EllipticalOrbit {
Obliquity 90.0
Period 10.005
SemiMajorAxis 10000
MeanLongitude 168.73
}

Albedo 0
}

[selden]

What do its axes look like when you delete the Orientation?

p.s. also please delete the RotationOffset to minimize the orientation confusion.
You might as well delete the CustomOrbit, too. CustomOrbits are orbits which are defined by mathematical functions internal to Celestia. They are available only for the planets of our Solar System and some of their moons. Any other CustomOrbit is just ignored, and thus only causes confusion for the person looking at the SSC.

[thepyratecaptain]

Well it seems the model orientation is just wrong to begin with so I guess I'm outta luck?

[selden]

Fixing a model's orientation in a 3D modeling program is relatively straight forward.
Where did you get it?

[thepyratecaptain]

The eagle? Starship, from the motherlode site. I downloaded blender, but have no clue on how to use it at all, kinda a noob, I tried once reorienting it, saved, exported, but all that showed in celestia was window panels, lol, guess I reinvented the scifi cloak?

http://www.celestiamotherlode.net/catal ... don_id=169
That's the eagle one.

Wishing I knew how to use the blender,

[selden]

Unfortunately, the models in that Addon were specifically oriented so they'd be parallel to the Moon's surface at the position of the crater Plato, simplifying the SSC for Celestia v1.3.2.

If you're using Windows, I found Anim8or to be much easier to learn than Blender.