Need help with orientation of 3ds models

[jim]

Hi all,

I have some problems with the orientation of my shuttle model in Celestia 1.3pre4. I've tried these commands:

Orientation [90 0 0 1]
Obliquity 200
LongOfRotationAxis 90
RotationOffset 90

but i can't find the trick. I've searched the forum for more infos about the Orientation command but nothing. Further seems that some commands works no longer or overlap with a other. The orientation should be possible with only 3 angels or not?

Can someone give an instruction?

Bye Jens

[Calculus]

Hi all,

I have some problems with the orientation of my shuttle model in Celestia 1.3pre4. I've tried these commands:

Orientation [90 0 0 1]
Obliquity 200
LongOfRotationAxis 90
RotationOffset 90

but i can't find the trick. I've searched the forum for more infos about the Orientation command but nothing. Further seems that some commands works no longer or overlap with a other. The orientation should be possible with only 3 angels or not?

Can someone give an instruction?

Bye Jens

For the orientation function:
The first figure, 90 in your example, is the angle in degres, then the 3 following figures are the xyz coordinates for the axis. In your case, you make a quarter turn around the z axis.
The other functions are parameters of the orbit and not really the orientation of the model.

[granthutchison]

First of all "LongOfRotationAxis" has been replaced by "EquatorAscendingNode", which has exactly the same effect, but the name more accurately reflects what the command does.

The easiest way to see what the various commands do is to go back to whatever Epoch you're using for your shuttle orbit - if no Epoch is defined, set the time to 1 Jan 2000 12:00:00, and comment out any AscendingNode, ArgOfPericenter or MeanAnomaly settings you might have.
You'll now find your shuttle model is sitting at Earth's EquatorAscendingNode - from the surface of the Earth it appears at zero right ascension. (Yes, I know that's actually the descending node of Earth's equator, but Chris has used a negative obliquity for the Earth, to force the zero of its orbital coordinates around to match zero right ascension.)

Orientation rotates an object around its X, Y or Z axis - Y at right angles to Earth's equatorial plane, X pointing along the line between the object and the centre of the Earth, and Z pointing parallel to its orbit (X&Z are only in these neat orientations at Epoch, which is why it's handy to get your model orientation sorted out at Epoch).

Obliquity tilts the object's rotation axis around the X axis. If you want the object to rotate in the plane of its orbit, set Obliquity = Inclination.

EquatorAscendingNode twists the object around in the plane of Earth's equator, keeping its Obliquity the same. If you want the object to rotate in the plane of its orbit, set EquatorAscendingNode = AscendingNode.

RotationOffset defines any further angular rotation of the object's prime meridian from the location it ended up in after the twisting caused by EquatorAscendingNode - the prime meridian starts off facing directly away from the Earth at Epoch, but is then moved by the EquatorAscendingNode command.

Grant

[Guest]

Hi all,

First my current SSC file:

"Columbia" "Sol/Earth"
{
Class "spacecraft"
Mesh "columbia.3ds"
Radius 0.020

EllipticalOrbit {
Period 0.06219
SemiMajorAxis 6628
Eccentricity 0

}

Orientation [90 1 0 0]
# Orientation [90 0 1 0]
# Obliquity 90
# EquatorAscendingNode -15

Albedo 0.10
}

I have still problems with the orientation off my model. My shuttle needs two 90degree rotations (x and y axis) but the Orientation command alow only one (Orientation [90 1 0 0] or Orientation [90 0 1 0]). If i use Obliquity or LongOfRotationAxis the shuttle spin in the orbit.

Something would be very easy if the Orientation command would have this syntax:

Orientation [x-angel y -angel z-angel]

Thanks for all the help.

Bye Jens

[granthutchison]

I have still problems with the orientation off my model. My shuttle needs two 90degree rotations (x and y axis) but the Orientation command alow only one (Orientation [90 1 0 0] or Orientation [90 0 1 0]). If i use Obliquity or LongOfRotationAxis the shuttle spin in the orbit.

Use RotationOffset, which is equivalent to a Y-axis rotation if Obliquity is zero:

Code: Select all

Orientation [90 1 0 0] # fix X-axis
RotationOffset 90 # fix Y-axis (or RotationOffset -90, if necessary)


You'll find most of these 2-axis problems are amenable to an X or Z reorientation followed by a RotationOffset.

The problem with your suggestion about Orientation is that the final orientation depends critically on the order you perform the rotations in. So you need a way to differentiate X-followed-by-Y from Y-followed-by-X. (Perhaps if Celestia understood multiple Orientation commands, and carried them out in the order typed?)
Also, if your brain can accommodate it, the Orientation command will work with a diagonal axis

Code: Select all

Orientation [90 1 1 0]


will rotate your object through 90 degrees around an axis midway between X and Y, which results in a two-axis reorientation. I find this impossible to hold in my head for more than a second, though, so I prefer to use the Orientation+RotationOffset solution above.

Grant

[jim]

Hy Grant,

Thanks for the help. Now i get it. I will upload on my website in the next days a new version off my (textured) Columbia shuttle. Since Chris has fixed some bugs and the new addon folder feature is available this revison was necessary. I will also upload a new version of the apollo lander. Now i put it on the possition of apollo 11 (thanks for this post: placing objects at defined locations on planetary surfaces).

Bye Jens

My page: http://www.angelfire.com/de3/jimpage/