How about playing with Titan's atmosphere parameters!?

[symaski62]

[t00fri]

symaski62,

that image is NOT relevant for the present discussion, since this is a false color composite in the infrared between 1.2 and 5 micron!

What did you think this image contributes to the issue of Titan's atmosphere composition in the /visible/ light range?

Bye Fridger

[symaski62]

symaski62,

that image is NOT relevant for the present discussion, since this is a false color composite in the infrared between 1.2 and 5 micron!

What did you think this image contributes to the issue of Titan's atmosphere composition in the /visible/ light range?

Bye Fridger

http://photojournal.jpl.nasa.gov/catalog/PIA08733



1.26 microns shown in blue, 2 microns shown in green, and 5 microns shown in red.

[t00fri]

symaski62,

that image is NOT relevant for the present discussion, since this is a false color composite in the infrared between 1.2 and 5 micron!

What did you think this image contributes to the issue of Titan's atmosphere composition in the /visible/ light range?

Bye Fridger

http://photojournal.jpl.nasa.gov/catalog/PIA08733



1.26 microns shown in blue, 2 microns shown in green, and 5 microns shown in red.

I just don't understand what you mean to say.
Just write in French! I carried a French passport once. This should suffice for understanding what you write.


Of course I was aware of that image. It is IRRELEVANT here, since it's a false color INFRARED composite.

Bye Fridger

[Fightspit]

I think he want to say that the different colors he has written (blue, red, and green, RGB) show the image in true color but it is not the case because of some color filters which is applied to the image.

[symaski62]

http://photojournal.jpl.nasa.gov/catalog/PIA07787

Ironically, what these two moons hold in common gives rise to their stark contrasting colors. Both bodies are, to varying degrees, geologically active. For Enceladus, its southern polar vents emit a spray of icy particles that coats the small moon, giving it a clean, white veneer. On Titan, yet undefined processes are supplying the atmosphere with methane and other chemicals that are broken down by sunlight. These chemicals are creating the thick yellow-orange haze that is spread through the atmosphere and, over geologic time, falls and coats the surface.

The thin, bluish haze along Titan's limb is caused when sunlight is scattered by haze particles roughly the same size as the wavelength of blue light, or around 400 nanometers.

[t00fri]

After plugging-in the above atmospheric constraints from the color composition of the "ring of light" and using the know parameters of Titan's atmosphere heights, I am now much closer to a realistic Titan atmosphere (modulo the bugs that still are in the code etc.).

Here is an amazing view of the delicate NEW atmospheric phenomena during a close flyby of (Spice_Cassini at Spice_Titan) on Feb 15 2005.
Spice_Cassini's altitude above Titan is about 1500 Km.

The "bright star" is Sol, but note the striking light scattering phenomena it causes left of Cassini...



Bye Fridger

[t00fri]

with the present atmosphere parameters, Titan's backlit ring_of_light compares as follows to Matt MacIrving's colored composite above:

Photo (top) : McIrving
Celestia (bottom)



This can of course still be tuned somewhat.

Bye Fridger

[ElChristou]

with the present atmosphere parameters, Titan's backlit ring_of_light compares as follows to Matt MacIrving's colored composite above:

Photo (top) : McIrving
Celestia (bottom)



This can of course still be tuned somewhat.

Bye Fridger

Not bad, but how looks the sunny face of Tittan with such settings?

[t00fri]

Now I did some further tuning with remarkable results.

Also the high atmosphere colors are coming out right
now.


The backlit ring of light


and the sunset on the Titan surface:


Bye Fridger

[tech2000]

Wow! Just stunning results you got there Fridger.

[Malenfant]

DEFINITLEY looks good

[ElChristou]

Yep, I really need to change my config to use the OpGL 2.0 path...

[dirkpitt]

Yep, I really need to change my config to use the OpGL 2.0 path...

Good idea

[t00fri]

After some further tuning, here are my -presently best - parameters for Titan's new atmosphere:

Atmosphere {
# Titan has a VERY high atmosphere ( 10x that of Earth!)
Height 500
Mie 0.0004
# larger (negative) MieAsymmetry than on Earth
# responsible for the conspicuous "ring of light"
# when atmosphere is backlit!

MieAsymmetry -0.55

# the Rayleigh RGB values indicate the color
# components visible in the highest part of the
# illuminated atmosphere

Rayleigh [ 0.0 0.0 0.0007 ]

# the Absorption RGB values specify the amount of
# absorption as visible in the backlit color composition
#of the "ring of light". R=0.0 means red remains! Etc.

Absorption [ 0.00015 0.0005 0.0004 ]

MieScaleHeight 220
CloudHeight 220
CloudSpeed 65
CloudMap "titan-clouds.*"
}

The atmosphere Height and CloudHeight values are from known measurements.

Here is a final account of what these parameters do:

Backlit ring of light and Titan at larger distance with faint blue halo on top of the orange haze.

Comparison of the detailed color bands with a Cassini natural color photo (see above)

Sunset from the surface (with haze activated)
Note the orange "ball" is NOT the sun, but a typical atmospheric effect around the position of the small-sized sun!


Bye Fridger

[Fightspit]

Good work
I can't imagine Titan more real

[chris]

Very impressive work, Fridger. I still need to fix a few things with atmospheres. The missing triangles is an obvious bug. Perhaps even more important is making it possible to have an opaque atmosphere--things just don't work correctly if the scattering values are too large. Ideally, it shouldn't event be necessary to define an opaque orange cloud layer for Titan. The atmosphere should do all the work of hiding the surface.

Once those two things are fixed, I want to make the new atmosphere code work for multiple stars--that should be fun to play with.

--Chris

[t00fri]

...
Ideally, it shouldn't event be necessary to define an opaque orange cloud layer for Titan. The atmosphere should do all the work of hiding the surface.
...
--Chris

How true! I was trying that of course initially, with little success...

That opaque haze layer of vanishing thickness is the main unsatisfactory aspect to date, when modelling Titan's atmospheric appearance from true color imaging constraints and knowledge of optics.

If we could get rid of it....

Bye Fridger

[PlutonianEmpire]

Wow.

Can't wait for the next release/pre-release!

[Malenfant]

Once those two things are fixed, I want to make the new atmosphere code work for multiple stars--that should be fun to play with.

--Chris

Hm, THAT would be very interesting to see!