About visibility of stars

[ElChristou]

Just a quick question:
let's say I'm at aprox 30000km from earth on my magic carpet; should I see the planet as pict 1 or more like pict 2?

[BrainDead]

Just a Brain-Dead reply, but shouldn't the stars appear brilliant outside of
the effects of the Earth's atmosphere?

I mean, if there's nothing in the way to block the photons, wouldn't you see
almost every particle of light from the distant stars?

Now you've gotten me curious too. Sorry, can't see any difference in the
Earth itself. Of course, I'm half-blind as well as Brain-Dead too.

Thanks, Bob

[ElChristou]

There is no differences in the earth, just in the stars around...
I just want to know if the light intensity of earth would not create a visual effect making stars diseapering or less visible than the normal...

[dirkpitt]

I just want to know if the light intensity of earth would not create a visual effect making stars diseapering or less visible than the normal...

You mean a glare or bloom effect, kind of like the halo that is drawn around stars right now?

[hank]

My guess is that if the earth is anywhere in your field of view, its brightness will cause your iris to contract, reducing the amount of light entering your eye from all directions. So only the brightest stars would be visible anywhere in your field of view. The effect would not be limited to a band around the earth's disk.

- Hank

[Malenfant]

Just a Brain-Dead reply, but shouldn't the stars appear brilliant outside of
the effects of the Earth's atmosphere?

I mean, if there's nothing in the way to block the photons, wouldn't you see
almost every particle of light from the distant stars?

Now you've gotten me curious too. Sorry, can't see any difference in the
Earth itself. Of course, I'm half-blind as well as Brain-Dead too.

Thanks, Bob

They'd be a bit brighter, but not THAT much - probably not enough to be called 'brilliant'. And they wouldn't twinkle because there's no atmospheric gas in the way.

But yeah, as Hank says, it's about your eyes reacting to a bright light source. In the view in the pictures, you wouldn't see any stars at all (not sure if you'd even see the nightlights for the same reason), and Earth'd be very bright (brighter than the full moon). And anyone who's been out at night when the full moon is up knows how hard it is to see stars around the moon - heck, even in the same half of the sky as the moon?

If you look away from the Earth though then you'd be able to see the stars (once your eyes got used to the darkness) - Hubble's in earth orbit and has the planet blocked from its view (it points away from Earth all the time) and it can see stars pretty well

This is one thing that needs to be simulated in Celestia if Chris is really going down the 'human eye response' route that he seems to be using.

[ElChristou]

My guess is that if the earth is anywhere in your field of view, its brightness will cause your iris to contract, reducing the amount of light entering your eye from all directions. So only the brightest stars would be visible anywhere in your field of view. The effect would not be limited to a band around the earth's disk.

I was thinking in this kind of phisiologic effect; now, someone has an idea on how to implement this?
Perhaps a kind of gradual black filter behind the body, with a size depending on the distance of the observer and always in the axis observer/center of the body?

Perhaps a black halo (as Dirkpitt said)?

It would be nice to do some test to see if the effect can be reproduced...

[Malenfant]

I was thinking in this kind of phisiologic effect; now, someone has an idea on how to implement this?
Perhaps a kind of gradual black filter behind the body, with a size depending on the distance of the observer and always in the axis observer/center of the body?

Perhaps a black halo (as Dirkpitt said)?

It would be nice to do some test to see if the effect can be reproduced...

It's hard to generate the actual brightness of the bright object in the monitor. But I guess you could simulate it by having the stars just either fade a bit as soon as the object is in view, or cut out of visibility completely as soon as Earth enters the view if you're this close.

[jestr]

Check this page of satellite photos of Earth,dont see many stars in the background,maybe our eyes would see differently?
http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-earth.html
Jestr

[ElChristou]

It's hard to generate the actual brightness of the bright object in the monitor. But I guess you could simulate it by having the stars just either fade a bit as soon as the object is in view, or cut out of visibility completely as soon as Earth enters the view if you're this close.

Yes , this solution seems to be a good one (is this possible at code level?), but when the distance between the observer and the body increase, the stars must return to their normal brightness.

As we can see in those photos pointed by Jestr, almost no stars are visible...
Definitively we have to try this...

[selden]

Not just stars, of course. Nebulae and galaxies become invisible, too.

[Cham]

Honestly, I don't see how this is related to Celestia. What's the point of having a space simulator which doesn't show the stars !??

I don't want to sound rude, but simulating the human eye response in Celestia is a nonsense to me. Put the ressources on more important things first (there are MUCH more important things to be implemented in Celestia) ! Just my 0.01 cent...

[ElChristou]

Honestly, I don't see how this is related to Celestia. What's the point of having a space simulator which doesn't show the stars !??

I don't want to sound rude, but simulating the human eye response in Celestia is a nonsense to me. Put the ressources on more important things first (there are MUCH more important things to be implemented in Celestia) ! Just my 0.01 cent...

Well if we are talking about the same thing (a space simulator) then this should be part of the simulation. If you are in space and see no stars when a major body is present then let's go. Having stars at all cost if the reality show the contrary sounds more like a SpaceOpera simulator... is this what we want?

Now, as we all want to see also lot of eyes candy (planet on a nebulae background, etc), perhaps this kind of utra realistic simulation can be optional (let's say only for purist)?

[BrainDead]

They'd be a bit brighter, but not THAT much - probably not enough to be called 'brilliant'. And they wouldn't twinkle because there's no atmospheric gas in the way.

But yeah, as Hank says, it's about your eyes reacting to a bright light source. In the view in the pictures, you wouldn't see any stars at all (not sure if you'd even see the nightlights for the same reason), and Earth'd be very bright (brighter than the full moon). And anyone who's been out at night when the full moon is up knows how hard it is to see stars around the moon - heck, even in the same half of the sky as the moon?

Appreciate the education here... Hadn't given any thought to the brightness
of the object Earth and its effect on your pupils. Amazing what a guy can
learn in this forum.

Thanks!

[Malenfant]

Honestly, I don't see how this is related to Celestia. What's the point of having a space simulator which doesn't show the stars !??

I don't want to sound rude, but simulating the human eye response in Celestia is a nonsense to me. Put the ressources on more important things first (there are MUCH more important things to be implemented in Celestia) ! Just my 0.01 cent...

Actually, I think this IS one of the most important things that should be implemented (along with photometrically accurate rendering) - it seems we're going down the 'human eye response' path anyway for multiple lighting and for removing the inverse square effect of illumination decrease with distance. If that is the case then when you look at a bright light source (be it emissive or reflective) close up then yes, the surrounding stars should be harder to see or fade out completely. That is what would happen if you fully implemented the human eye response, and it is in fact the most realistic way to treat it. It's what we'd see - the fact that we can still see stars around big, bright objects is a major flaw in the program right now (another side of this flaw is that that we aren't seeing an oversaturate glare when we're looking at a star closeup - we should be seeing a brilliant white disk and no other stars in the screen at all)

[dirkpitt]

Is the real reason why I still see stars when I look at Earth or the Sun in Celestia is because my monitor is not bright enough (I'm not "blinded" enough), or are the stars themselves possibly rendered too brightly?

[Malenfant]

Is the real reason why I still see stars when I look at Earth or the Sun in Celestia is because my monitor is not bright enough (I'm not "blinded" enough), or are the stars themselves possibly rendered too brightly?

The problem is that it's not realistic. The monitor CAN'T render the Earth realistically bright, but there's currently no way to account for the simulated brightness of nearby objects. So the stars are being rendered too bright in comparison to the source of nearby illumination.

The 'human eye response' simulation is incomplete, basically. It's only implemented for multiple star lighting and in accounting for decrease in brightness.

A better way to render stars for example would be how the MMORPG EVE Online does it:





See how it's just one big bright glare? That's what you should be seeing when you're close to a star. (ignore the nebula clouds etc there). It is certainly possible to SIMULATE the brightness of stars. It's harder to do that with planets without washing out all the features though. But for stars, if you had a glare like this with a washing out of the stars around the light source it'd be a darn sight more realistic.

[ElChristou]

If on day stars are rendered like in those pictures, then a filtering system become almost essential to see flares, spots etc... with this Celestia would gain a really high and impressive level of realism...
Curiosity: are those Nebulae clouds in pict 1 in 3D real time?

[Malenfant]

If on day stars are rendered like in those pictures, then a filtering system become almost essential to see flares, spots etc... with this Celestia would gain a really high and impressive level of realism...
Curiosity: are those Nebulae clouds in pict 1 in 3D real time?

That'd be more elegant, yes.

And no, the nebula clouds are just background in EVE, they're not in 3D. But they're very pretty

[hank]

A better way to render stars for example would be how the MMORPG EVE Online does it: ...

See how it's just one big bright glare? That's what you should be seeing when you're close to a star. (ignore the nebula clouds etc there). It is certainly possible to SIMULATE the brightness of stars. It's harder to do that with planets without washing out all the features though. But for stars, if you had a glare like this with a washing out of the stars around the light source it'd be a darn sight more realistic.

"Better" is a matter of opinion, I guess. I'm more interested in Celestia as a visualization tool than as a visual simulation.

And actually, if you looked at a star from that close, you'd probably be permanently blinded. That's easy to simulate with your current monitor: just switch it off. :-)

- Hank