Celestia Forums

Suppose I want to write a deep space catalog for a nebula. What is the formula for determining the axis and the angle of the space object?

Polchey wrote:Suppose I want to write a deep space catalog for a nebula. What is the formula for determining the axis and the angle of the space object?

Your one-line question is certainly quite ill-defined...

I am working on a very large galaxy catalog (25000+ galaxies) since several weeks. I do have the completely general solution of the Axis, Angle alignment problem.

But it's a vaste of time to even start off with all this, if you don't manage to sit down and describe precisely what you have in mind...There are necessarily several different coordinate frames involved in this problem and you have a series of transformations (rotations) to do to connect them...

Which parameters you want to input in what frame? What tools you want to use? (C++, PERL,...), what deep-sky catalogs you want to use as input... You need to work with quaternions, of course...So you need an environment that supports them.

The task is not quite trivial, if you have no solid math training and are not an expert in such things, which would also be a useful piece of information to convey ...

Bye Fridger

I'm just tinkering around with how the coding for these Celestia files work, so it's none of your concern that that I should tell you precisely what I have in mind. All I need is a tutorial that descibes how to align the objects. Yes, it would be a waste of time for you describe to me how to do this when I could read a tutorial from somewhere how to do this.

Polchey wrote:I'm just tinkering around with how the coding for these Celestia files work, so it's none of your concern that that I should tell you precisely what I have in mind. All I need is a tutorial that descibes how to align the objects. Yes, it would be a waste of time for you describe to me how to do this when I could read a tutorial from somewhere how to do this.

May I remind you that Celestia is NOT commercial software where people are paid for writing tutorials! I am not at all interested in what you specifically want to do. But if you want my time, I prefer to spend it economically. That's all.

People unwilling to pose clear questions, cannot expect to get much help.

The answer to your question is much too involved for a general tutorial, of course. Also there are different kinds off applications that require different solutions:

-- alignment of individual deepspace objects on a mesh. That problem is easy and there exists an EXCEL form to generate the Axis,Angles. But you did not ask for this, did you?

-- generation of whole catalogs from particular catalog parameters. That problem is quite involved. Answers surely depend on the specific needs. Since they are not of my concern I am going to stop here....

Bye Fridger

t00fri wrote:I am going to stop here....
Bye Fridger

Good !
Why did you not do that before you started
and thus spare us all yet another demonstration of how the universe and questions in Celestia forum should be modeled upon Fridger's requirements ?

Suggestion : if you do not like the way a question is asked then do not answer it, leave it to someone else, go take a tranquiliser instead and spare us all your bad humours.
Thank you.

Polchey : Sorry, I dont know the answer to your question ! but :I will be interested in anyone's answers that can develope this subject with good grace

My approch to this is as we do when we go to the doctor, we can ask for a second opinion. You may be right, but I' not giving up that easily. Maybe someone else is able to answer my question. I'll try this post again a later time and see who else answers.

Polchey wrote:My approch to this is as we do when we go to the doctor, we can ask for a second opinion. You may be right, but I' not giving up that easily. Maybe someone else is able to answer my question. I'll try this post again a later time and see who else answers.

Yes do that

t00fri wrote:Yes do that

D**mn
I could have swore I saw him type
"I am going to stop here"
earlier.
Obviously he can not even take his own advice, so what chance do the rest of us have to influence him ?

(Fridger, I hope you won't loose much time on this...)

Polchey,

As Fridger pointed out, there are different kinds of alignments you might be talking about. If you don't describe your problem, people can't help.

If you just want to adjust a picture so it looks good in Celestia, then you might take a look at [url]http://www.lepp.cornell.edu/~seb/celestia/billboard.html]/url]

However, if you want to align objects algorithmically in space, then you need to take a course in 3D trigonometry. If you don't understand the underlying math, tutorials won't do any good. If you do understand the math, then you don't need a tutorial.

Ok Selden, you know how to answer a question.

Polchey wrote:Ok Selden, you know how to answer a question.

... except that he has not told you the formula you were after...