Binary star system screen shots

[chris]

Here are a few screen shots from Celestia that show off the new support for multiple star systems. Of course, it's much more interesting to actually see the stars moving in orbit around each other.

The (fictional) Nyx system shown in these shots consists of two stars which orbit each other at an average distance of about 40au. Nyx A is a 1.4 solar mass star that has evolved to the red giant stage. Nyx B is a main sequence G class star very much like our Sun. The terrestrial planets Clotho and Lachesis orbit Nyx B at 0.7au and 1.2au. From Lachesis, the red giant Nyx A appears as bright as Nyx B even though it's 40 times further away.

Clotho is illuminated by both Nyx B (visible in picture) and Nyx A, leaving just a slice of the planet in darkness:


Lachesis, lit by two suns. I used Runar's Blue Venus textures for this planet.


A double sunset on Lachesis. Note that Nyx A appears larger than Nyx B. Even though Lachesis is 40au from Nyx A, the red giant has an apparent diameter over three times that of the Sun in our sky.


--Chris

[Evil Dr Ganymede]

Ooh. Spiffy!!

Lachesis, lit by two suns. I used Runar's Blue Venus textures for this planet.

Now THIS is what I'm talking about!!
What I'd be really interested to see is shadows on the planets. If you get two different coloured light sources (say, a red giant and a blue star) slightly displaced from eachother in the sky, and you have something casting a shadow (ideally a mountain or something, but in this case I guess a moon casting a shadow on a planet would work) from both stars, you should see something called the Flamarrion effect. Funnily enough, I explained what this was on this very forum over a year ago:

IIRC the Flammarion effect is when you get two lightsources (usually of different colours) illuminating a surface. The picture I've seen (I can't remember where I saw it - I think it was in a space art book) was of a mountain or something on the planet's surface, illuminated by a red giant and a blue/white dwarf. You get two shadows of different colours cast by the mountain - where the red light is blocked and the blue light isn't, the 'shadow' is coloured blue, and vice versa. And where both lights are blocked, you get a black shadow.

So do you see that in your binary systems at all?


It all looks utterly great though... I can't wait to get my mitts on a public version . How many nearby light sources can it cope with? Just two?

[Guckytos]

Abolute cool!!

Can't wait to get my hands on this new version. But on the other hand i have first to finish 800 star placements for an addon.
The two suns over the planet look just awesome.

[Brendan]

Wow! I can't wait to see it in motion.

Brendan

[Rassilon]

I guess Im going to have to start modding again...

btw does this also affect bumpmaps specular highlights and nightside lights?

[rthorvald]

Here are a few screen shots from Celestia that show off the new support for multiple star systems

Wonderful!
I really hope it makes it into the OSX version soon
I?m tempted to get a PC just for Celestia...

-rthorvald

[Dollan]

Oh, NICE. Definitely looking forward to this!

...John...

[Evil Dr Ganymede]

Is there any falloff in illumination based on distance? (e.g. is the illumination of a hemisphere lit by a nearby primary more pronounced that the illumination from a distant companion that's over 1000 AU away?)

(I'm not expecting that there is, given that this doesn't happen normally in celestia, but I thought it'd be cool )

[TERRIER]

Chris,

Fantastic, this'll get me out of the solar system more often !

Any noticeable 'slow-down' when viewing the two star system (or greater), compared to a single star system ?

btw does this also affect bumpmaps specular highlights and nightside lights?

Yep, this is a good question.

regards,
TERRIER

[chris]

Is there any falloff in illumination based on distance? (e.g. is the illumination of a hemisphere lit by a nearby primary more pronounced that the illumination from a distant companion that's over 1000 AU away?)

(I'm not expecting that there is, given that this doesn't happen normally in celestia, but I thought it'd be cool )

Yes, the brightnesses of the light sources are scaled relative to each other. My reasoning for this is that the eye will adapt to the brightest light source illuminating the planet. Thus Pluto still doesn't appear any dimmer than Earth when viewed from the same distance. But a planet illuminated by two identical stars with one at 1au and another at 40au would be rendered with bright light from the close star and just a faint contribution from the more distant star. The scaling of brightness is deliberately non-linear in order to approximate what the human eye would see.

Currently, only two light sources are supported. They're sorted so that only the brightest two are selected. I plan to add support for at least three in the existing vertex shader path, and more with a new advanced shader path that I'm working on. Are there realistic situations where more than three would stars could visibly illuminate a planet?

Night maps and bump maps aren't yet working with multiple light sources. Neither are atmospheres or eclipse shadows. I plan to address all of this in the next couple of weeks.

--Chris

[Evil Dr Ganymede]

Yes, the brightnesses of the light sources are scaled relative to each other. My reasoning for this is that the eye will adapt to the brightest light source illuminating the planet. Thus Pluto still doesn't appear any dimmer than Earth when viewed from the same distance. But a planet illuminated by two identical stars with one at 1au and another at 40au would be rendered with bright light from the close star and just a faint contribution from the more distant star. The scaling of brightness is deliberately non-linear in order to approximate what the human eye would see.

Awesome!

Currently, only two light sources are supported. They're sorted so that only the brightest two are selected. I plan to add support for at least three in the existing vertex shader path, and more with a new advanced shader path that I'm working on. Are there realistic situations where more than three would stars could visibly illuminate a planet?

Hmm. Three is probably about as many as you'd expect... I mean, looking at the Spica system I made, you have the main lightsource being the K5 V star that the planet orbits, and the four other B V stars are far enough away and close enough together in the sky that effectively they're one light source. So I think you'd be OK in practise with a limit of three light sources.

Is there a distance limit for the lighting? Like, if the light source drops below a magnitude of (for example) -10 as seen from a planet then it wouldn't illuminate a hemisphere there?

Does all this stuff slow Celestia down in any noticeable way, BTW?

[kikinho]

If I download this new version of Celestia with this new feature now or in the next days, I think that I will put another star in my Rabud system, maybe another very small W5V star with it's own system...

Chris, thank you for all your efforts. I know that still this year Celestia will be much better than it was a year ago.

[kikinho]

Chris, could you please send me more pictures, like how would be a planet illuminated by a brown dwarf: L5V star and a blue star? And could you send me an image showing the orbit of the stars with the orbit of a planet?

[selden]

kikinho,

The features you're asking about don't work yet.
(Today, shadows are all the same color and Celestia does not yet draw orbits for stars.)

Patience!

[kikinho]

When I see my system and approach another star, my system disappear. Now I know that Celestia still cannot draw orbits to stars, but what I want to know now is if Chris is working for a system support multiple stars. I'm starting now adding very near stars to my Rabud star, and the thrid system I'm doing orbits two stars.

[Rassilon]

bump maps aren't yet working with multiple light sources.

I didnt figure as this is a pain in the arse enough with one light source...imagine all 8....

[Evil Dr Ganymede]

When I see my system and approach another star, my system disappear. Now I know that Celestia still cannot draw orbits to stars, but what I want to know now is if Chris is working for a system support multiple stars. I'm starting now adding very near stars to my Rabud star, and the thrid system I'm doing orbits two stars.

Well, yes. That's the point of this thread - for Chris to show off the work that he's doing on adding support for multiple stars and illumination from them.

As Selden said, you just have to be patient. Wait til he's done, and then see what support is there. I'm sure you'll be able to do most of what you want to do.

[chris]

When I see my system and approach another star, my system disappear. Now I know that Celestia still cannot draw orbits to stars, but what I want to know now is if Chris is working for a system support multiple stars. I'm starting now adding very near stars to my Rabud star, and the thrid system I'm doing orbits two stars.

With my changes for multiple star systems I've removed the limtation where only the planets orbiting the closest start to camera were shown.

--Chris

[chris]

Here's another shot of Lachesis that shows night lights behaving correctly when the planet is illuminated by two suns:



--Chris

[Evil Dr Ganymede]

(Today, shadows are all the same color

So in the "multiple star lighting" version of Celestia the shadow from a moon eclipsing one star is totally black, even if it's cast on a hemisphere that is lit by another star of a different colour?

BTW, nice work with the night lights, Chris!