Celestia Forums

Hi all:

I was wondering how difficult it would be to create a short "shooting star" add-on. When viewed from Earth, a meteor/shooting star streaks across a few degrees of sky and disappears ... visible for no more than 2 seconds. Just a streak of light really, moving fast.

I suppose this could be done by placing an object in very low orbit around Earth and setting the period very short, with a 2 second beginning and ending. One would see a moving "dot" for 2 seconds, then end. That would not produce a "streak" or meteor trail, however. I have no idea how to create that, but if it could be done, it would be a very neat little add-on. Folks could change the times, or the orbital parameters to suit them or copy and pste it into their own add-ons.

Another approach would be to do it via an XYZ file, with 30 data points per second. Two seconds (60 data points) might be adequate to give the idea of a streak of light, assuming Celestia could draw it as separate frames ... :-\

Any ideas? Would anyone be willing to give this a go?

Frank

fsgregs wrote:Any ideas? Would anyone be willing to give this a go?

Hm... I suppose a good way could be to make a few hundred asteroids. Then one can follow them from some time before the Earth encounter, for some added fun. When they hit the atmosphere we??ll make them emissive for a few seconds, and a script that zooms out and moves the camera to the ground.

It is a nice idea. I could look at it later: i have my hands full right now, but later in the summer...

Of course, doing it this way will not make any sense for screenshots: the "shooting star" effect is only going to be there when one runs Celestia in normal time.

- rthorvald

It is a nice idea. I could look at it later: i have my hands full right now, but later in the summer...

Great!

In the interim, perhaps we could start with just one. I'm not sure how to get a streaking effect with emissive true. If you can suggest what I might have to do in an ssc file to get a 2 second "streak", I can give it a try.

Frank


Frank

fsgregs wrote:If you can suggest what I might have to do in an ssc file to get a 2 second "streak", I can give it a try

I thought wrong, i think: i thought if it was moving fast enough, you would percieve it as a streak. But that won??t work... No matter, though - there is probably a way:

Create an SSC file (much less work than the xyz) that have the asteroid enter the atmosphere. The moment it does, replace it with an emissive one with a reddish atmosphere. Duplicate it, so that it gets say 50 duplicates backwards, each one a little smaller than the previous. Give each one a fraction of a second shorter lifespan, with all of them starting simultaneously, then dropping of from the last one to the first (counting away from Earth).

If you use a very small texture - say 64x64 px - Celestia should be able to load all of this and display it properly.

- rthorvald

Runar:

Thanks for the guidance. I am still a novice in writing complex ssc files, but I will give this a try.

Two questions:

1. What would I type to generate an Earth orbit that starts far out in space and enters Earth's atmosphere? I am OK with regular circular orbits, but I am totally bad at knowing which commands create elliptical orbits with a perigee that is within 100 km or so of Earth (inside out atmosphere).

2. Just as an aside ... do you ever sleep??? Norway is six hours ahead of Virginia, and your last post was at 9:42 PM EST, making it almost 4:00 AM in Norway.

Now THAT is Celestia dedication!!!

Frank

fsgregs wrote:1. What would I type to generate an Earth orbit that starts far out in space and enters Earth's atmosphere?

You could start out with duplicating Earth??s orbit, and then just slow down or speed up the asteroid slightly (change the Period). Then it would intercept the Earth somewhere over the course of one year, but it will come down head-on. To change this, just make the SemiMajorAxis a tiny bit larger or smaller.

fsgregs wrote:Just as an aside ... do you ever sleep?

Sleep? What??s that?

- rthorvald

Frank,

check out Jestr's and my Add-On "The War Of The Worlds" -> http://celestiaproject.net/forum/viewtopic.php?t=9633

There is a shooting star already in the 2nd part of the tour.

Adirondack