Atmospheres with Multiple Star Lighting

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Spectre_08
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Atmospheres with Multiple Star Lighting

Post #1by Spectre_08 » 18.11.2005, 01:28

Hello all. I've got a question about a possible development issue.

Basically what I'm trying to do is create an add-on of a binary system with an earth-like planet lit by 2 G type stars (ie Sol/Lucifer from 2010: Odyssey 2). The problem I'm having is while the clouds and surface of the planet are perfectly lit by the two stars, the atmosphere is only rendered for one star.

Example 1:
Image
*Earth2 and Saturn 2 are backlit by the other star, but the atmosphere effects are only rendered from the star shown in this image.

Example 2:
Image
*The sky is black on one side and blue on the other, even though both sides are about equally illuminated.

Example 3:
Image
*This example shows the atmosphere effects from the surface of the planet. Even though both stars have about the same app mag from the surface, only one side gets the sunset effect (top). In the lower-left frame, everything except the sky is illuminated. On the other side of the planet (lower-right) the sky is properly lit.


So my question is, is it possible to change the code to allow simultaneous atmosphere effects for more than one star at a time?


Note: In my test system, I placed Earth2 in an orbit around Saturn2, which orbits one of the two binary stars (HB1). The other binary (HB2) is 3x as far from Saturn2 as HB1, but is 3x more luminous so (in my limited understanding of astronomy) both planets should get about equal lighting when in between the two stars. Also, all images were captured directly with no modifications.

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Post #2by PlutonianEmpire » 18.11.2005, 05:00

This looks like an interesting topic :)
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Post #3by Tleilax » 20.11.2005, 02:07

Damn! I never noticed that before! I have a simular addon with a planet orbiting 2 stars and the atmosphere is only rendered for the Alpha star? I have no idea how to fix it...
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Post #4by Boarder » 10.02.2006, 20:16

I'm having the exact same trouble, trying to make a 2010 addon... I have Jupiter (now lucifer) set to emissive true, but I'm still getting light on the moons from Sol, not the new star.

Any ideas? Is there a way to set something as a "star" besides Emissive true? On this topic, wherever is the data for Sol stored? Can't find it anywhere! :P

Thanks to anyone who can lend a hand! :)

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selden
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Post #5by selden » 10.02.2006, 20:42

Objects that are "Emissive true" do not emit any light. They just look like they do. That feature was a quick hack for use until Celestia could be upgraded to support orbiting stars.

Star orbits were added in Celestia v1.4.0, so now you can put a real star in that orbit.

Descriptions of the relevant new STC catalog features are available in several locations, including the documentation page on the Motherlode. A brief summary is available at http://www.lepp.cornell.edu/~seb/celest ... eters.html

p.s. Sol is defined in the binary file stars.dat, but more detailed parameters for Sol are in /data/nearstars.stc
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Post #6by buggs_moran » 10.02.2006, 21:04

selden wrote:Objects that are "Emissive true" do not emit any light. They just look like they do. That feature was a quick hack for use until Celestia could be upgraded to support orbiting stars.



That evil non emissive Emissive true.

Maybe it should be Diffuse true or Ambient true?
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Post #7by Boarder » 10.02.2006, 21:27

Confused I am.

I've added "Lucifer's" data to Nearstars but it's not showing up (I deleted Jupiter / Lucifer from solarsys ...

I don't suppose any of you nice people would want to copy paste here what Jupiter's orbit should be, and how to get Celestia to recognize it as a star... I'm new at this :P

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selden
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Post #8by selden » 10.02.2006, 21:44

You shouldn't edit any of the data files that come with Celestia. They'll get overwitten if you upgrade Celestia into the same directory.

Instead, create an SSC file in your Addon's directory which effectively eliminates Jupiter, and an STC file which defines the star that replaces it. (Unfortunately, I don't think Beginning and Ending work in STC catalogs.)

NoJupiter.SSC

Code: Select all

Modify "Jupiter" "Sol" { Class "invisible" }


Lucifer.STC

Code: Select all

 Star "Lucifer" {

SpectralType "G2V"
OrbitBarycenter "Sol"
Radius 71500
AbsMag 8

   CustomOrbit "vsop87-jupiter"
}


Unfortunately, this seems to trigger a bug that causes all of Jupiter's moons to flicker. I haven't spent any time on this, so there may be a way to work around this problem.

p.s. I'm moving this thread to the Bugs forum, since that's what these are.
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Post #9by Boarder » 10.02.2006, 22:11

Most excellent! Many thanks, that did the trick just fine. I deleted Jupiter from Solarsys instead of making it invisible, I suspect that was the cause of the flickering?

Thanks again :)

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Post #10by selden » 10.02.2006, 22:15

I suspect that's the source of the problem:
Celestia is drawing the relatively dark moons orbiting Jupiter at the same time it's drawing them illuminated by Lucifer.

*grumble*

p.s.
Note that the moons do need to be orbiting something. Presumably you can define them again but orbiting Lucifer.
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Post #11by Boarder » 10.02.2006, 23:45

selden wrote:p.s.
Note that the moons do need to be orbiting something. Presumably you can define them again but orbiting Lucifer.


I have most of the moons, but a lot of them (the smaller ones) are missing... I can't seem to find them ... any idea where the data on Jupiter's moons is stored?

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Post #12by selden » 11.02.2006, 12:24

Many are in /extras/minormoons.ssc

(It really should be in /data/. Maybe that'll happen in the release of Celestia.)

More are available in
http://cvs.sourceforge.net/viewcvs.py/c ... dmoons.ssc
See also
http://www.lepp.cornell.edu/~seb/celest ... moons.html
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Post #13by Boarder » 11.02.2006, 20:44

Thanks so much Selden, you've been a great help. I was *so* stumped on this.

Hugs!


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