Celestia Forums

http://ciclops.org/view.php?id=1736

Are there any plans to simulate "ringshine" in Celestia? i.e. light reflected onto the planet from the rings around it. It'd only be applicable for extensive icy ring systems like Saturn's though. But it's an interesting sight to see....

Yes, I would like to add ringshine to Celestia. But before looking at that I plan to add planetshine.

--Chris

Rings in Celestia have currently no thickness, so edge-on view does not render anything that makes sense.
The dim glow onto the atmosphere ... that's another story.
Maybe an addon with:
- a very thin (really thin) cylindrical mesh wrapping the outer ringss with an emissive texture mapped on its outer side
- a mico-star locked on the dark side to bring some light there
I am not even sure that a secondary light source would work.

I thought planetshine was albeido...

Buggs,

Do you mean albedo?
That's a measure of how much light a surface will reflect when it's illuminated.

"Planetshine" is the light itself.

The higher a planet's albedo is, the brighter its "planetshine" will be, but the amount of planetshine also depends on how much of the planet's surface is illuminated from the point of view of the object being shined upon.

Boux wrote:Rings in Celestia have currently no thickness, so edge-on view does not render anything that makes sense.

That's easily solved - just give the rings a thickness

The dim glow onto the atmosphere ... that's another story.
Maybe an addon with:
- a very thin (really thin) cylindrical mesh wrapping the outer ringss with an emissive texture mapped on its outer side
- a mico-star locked on the dark side to bring some light there
I am not even sure that a secondary light source would work.

Nope. In the first case, the ringshine would be variable, depending on the tilt of the rings relative to the star, so your mesh would have to be changing too. In the second case, the dark side would be entirely (dimly) illuminated, not just in a band.

It needs to be something that can respond to the illumination angle. And it's interesting to note that there's light from the rings visible above the unilluminated side of the rings, implying that there is some scattering taking place through the rings (though most of the illumination is in the bottom half of the planet, where the rings are facing the sun and reflecting light directly onto the planet).

buggs_moran wrote:I thought planetshine was albeido...

Nope. Albedo is just a measure of the reflectivity of the planet - an albedo of 1.0 is a perfect reflector, 0.0 is a perfect absorber (blackbody). Planetshine (like the earthshine that you see when you look at a crescent moon) is when light reflects off a planet to illuminate the darkside of a nearby body. Ringshine is when light reflects off rings to illuminate the darkside.

selden wrote:Buggs,

Do you mean albedo?
That's a measure of how much light a surface will reflect when it's illuminated.

"Planetshine" is the light itself.

The higher a planet's albedo is, the brighter its "planetshine" will be, but the amount of planetshine also depends on how much of the planet's surface is illuminated from the point of view of the object being shined upon.

One of those times spell check would come in handy (granted I do NOT rely on spell checkers since they're tendency to bee wrong is sew prolific. ) Anyway, thanks for the explanation Selden & Malenfant.

PS does anyone else have anything to say about my animation post??? http://www.shatters.net/forum/viewtopic.php?t=8712