I took the data for scale height from here: Scale height but it’s difficult to apply, I didn't use the correct value always. Also I’d appreciate explanations on what the parameter actually do. Changing them gives somewhat unpredictable results, so it’s difficult to get the appearance you want.
- Height: This parameters seems useless for scatter-rendered atmospheres, but the value determines if Celestia bothers rendering the vertical profile of the atmosphere. So high values and the atmosphere shows up correctly even at high distances.
- Mie: The amount of Mie-scattered light. It gives a hazy appearance, but I don’t understand Mie theory to be honest. Pushing the value to high makes the atmosphere go crazy instead of giving a thick appearance. Low values don’t quite give a desired look of a thin atmosphere, like for Pluto.
- MieScaleHeight: Pretty much what it says. But it appears that a high value also makes the atmosphere go crazy thick instead of just scaling it vertically.
- MieAssymetry: determines the amount of forward- and back-scattered light.
- Rayleigh: The amount of red, green and blue light scattered by Rayleigh-scattering. In reality, it is proportional to (1/wavelength)^4. Using r=630nm, g=540nm and b=450nm I get relative intensities of r:g:b = 0.260:0.482:1. Also it seems Rayleigh scattering uses the MieScaleHeight parameter for scale height.
- Absorption: the amount of red, green and blue light absorbed.
Added after 4 minutes 44 seconds:
Gas giants
After finding the look I wanted, I pretty much copied it for each planet with minor adjustments. I went with a hazy atmosphere, little Mie backscattering and medium Rayleigh scattering. For the ice giants, I used a higher scale height than measured. Feel free to find a combination of parameters that works for the correct scale height.
Jupiter:
Code: Select all
Atmosphere
{
Height 1000
Mie 0.002
MieScaleHeight 27
MieAsymmetry -0.1
Rayleigh [ 0.00065 0.0012 0.0025 ]
}
Saturn:
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Atmosphere
{
Height 1000
Mie 0.001
MieAsymmetry -0.1
MieScaleHeight 59.5
Rayleigh [ 0.00026 0.00048 0.001 ]
}
Uranus:
Code: Select all
Atmosphere
{
Height 500
Mie 0.001
Rayleigh [ 0.00026 0.00048 0.001 ]
MieScaleHeight 60
}
Neptune:
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Atmosphere
{
Height 500
Mie 0.001
Rayleigh [ 0.00026 0.00048 0.001 ]
MieScaleHeight 60
}
Added after 4 minutes 10 seconds:
Hazy words
Venus and Titan feature thick cloud layers blocking the view from the surface. It’ll be great the find parameters that reproduce this phenomenon without a cloud texture, but I haven’t succeeded. The parameters would apply for height above the clouds, also the cloud height is much greater than the scale height. So the high cloud texture seems vastly unimpressed by atmospheric effects, which is not the case in reality. For Venus, I used the parameters of one of John Van Vliet’s addon as a start, but haven’t really improved anything. For Titan I was quite happy with my results at first, but can’t quite get what I see in Cassini images. I want the atmosphere to start at the cloud tops, so I defined a “cloud” object and gave it Titan’s atmosphere. Downside is I can’t toggle the clouds anymore… Note also that I’m using a grey cloud texture to blend with my defined color.
Venus:
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Atmosphere
{
Height 100
Mie 0.001
MieAsymmetry -0.1
Rayleigh [ 0.00001 0.0 0.0 ]
Absorption [ 0.00025 0.0003 0.0005 ]
MieScaleHeight 48.5
CloudMap "venus-clouds.*"
CloudHeight 48.5
CloudSpeed 90
}
TItan:
Code: Select all
Atmosphere
{
Height 190
Mie 0.0001
MieAsymmetry -0.25
Rayleigh [ 0.00026 0.00048 0.001 ]
MieScaleHeight 150
CloudHeight 190
CloudSpeed 65
CloudMap "titan-clouds.*"
}
Titan "Cloud Planet":
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Replace "Titan:Saturn VI" "Sol/Saturn"
{
Texture "titan-radar.*"
Radius 2576
Color [ 1.00 0.88 0.57 ]
BlendTexture true
Albedo 0.21
CustomOrbit "titan"
BodyFrame { EquatorJ2000 {} }
CustomRotation "iau-titan"
}
"Titan Clouds" "Sol/Saturn/Titan"
{
Texture "titan-clouds-grey.*"
Radius 2780
Color [ 1.0 0.85 0.5 ]
BlendTexture true
Albedo 0.21
Clickable false
FixedPosition [ 0 0 0 ]
RotationPeriod 100
Atmosphere
{
Height 500
Mie 0.0001
MieAsymmetry -0.55
Rayleigh [ 0.00020 0.00036 0.00075 ]
MieScaleHeight 80
}
}
Added after 2 minutes 48 seconds:
Thin atmospheres
Pluto looking quite realistic already, but what bothers me is the Absorption ruins the color balance of my surface texture. Not much luck with Triton yet, but I don’t have any references. I’d just like to see a faint haze.
Pluto:
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Atmosphere
{
Height 130
Mie 0.0001
MieAsymmetry -0.4
Absorption [ 0.000300 0.000300 0.00000 ]
MieScaleHeight 60
}
Triton:
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Atmosphere
{
Height 22
Mie 0.0001
MieAsymmetry 0.2
MieScaleHeight 8
}
Added after 1 minute 15 seconds:
Mars
Using inverse Rayleigh parameters (more red light scattered than blue) for a brown sky and blue sunset.
Code: Select all
Atmosphere
{
Height 80
Mie 0.002
Rayleigh [ 0.0017 0.00082 0.00044 ]
MieScaleHeight 11.1
CloudMap "mars-clouds.*"
CloudHeight 30
}
