Celestia Forums

I was thinking of making a plugin that would change the image of certian objects, such as Earth, depending on the time read on the clock. I.e., if the time is -250 My then I would show Earth as an image of Pangea, where as -500 My I'd show the continent of Baltica. So the idea would be, I need a call-back hook of some kind that can say: "When time crosses this threshold, display this". So, for like +1 Gy, I could show Sol as a Red Giant. Also, is it possible to take lunar drift into account? That is, to show the moon receeding from the Earth over time, and run backwards show it closer? And further, would it be possible to slow down Earth's spin to correspond with the lengthing of the day over time. Is any of this possible via a plugin? Thanks!

There's no need to be so elaborate, except as a demonstration of Lua capabilities, of course.

The SSC Beginning and Ending directives specify when an object should be drawn by Celestia. You just need to define the different objects with everything identical except for their textures and Beginning and Ending times.

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Celestia is not currently designed to show continuously changing orbits over such a long period of time: the VSOP87 and JPL ephemerides are good for only about +/- 3000 years around the current date.

However, you can use the Beginning and Ending directives to enable SSC catalog entries that have different Keplerian orbital parameters and rotational speeds at different epochs. The orbits won't change continuously between those dates, of course.
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selden wrote:The SSC Beginning and Ending directives specify when an object should be drawn by Celestia. You just need to define the different objects with everything identical except for their textures and Beginning and Ending times.

Oh, cool! So then I say Moon exists from say -50 My to +50 My at distance from Earth x, then a different moon exists from say -150 My to -50 My at distance y and so on. Thanks!