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"Neat" Pictures

Dr. Anomaly

By Dr. Anomaly
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Cancer Grand Master

Cancer

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Re: "Neat" Pictures

 

I sometimes fool around in Photoshop as a way to clear my head. Here is what I came up with this time.

 

Cancer, is this a feasible planet/picture? :D

 

Nothing wrong with that.

 

Strong scattering of light in the atmosphere, of the same color as the planet surface, suggests lots of dust: very windy there. Is it that way all the time, or is this a special season? No clouds to speak of, which suggests a pretty low-density atmosphere, too. And the edge of the light-scattering layer is the top of the troposphere/bottom of the stratosphere.

 

No lights on the dark side, so the surface, at least, is not heavily populated. The terminator isn't a nice circular arc, so there's substantial altitude differences along the terminator ... that indicates a smallish, low-gravity world, which is OK with the atmosphere things above. No obvious shorelines or bodies of liquid on the surface -- the albedo features don't have sharp edges, and what relief I see looks consistent with impact features, again suggesting a thin atmosphere and little weathering going on.

 

You might add some hints of aurorae (those should be greenish and/or reddish) near the one of the poles (magnetic poles, which don't have to be same as the rotation poles, but it's likely those will be more or less the same), in the dark parts. Daylight will swamp the auroral glow.

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RPMiller Mentor

RPMiller

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Re: "Neat" Pictures

 

VERY COOL!!! Thanks Cancer!! I'm going to try my hand at creating some additional planets, and I'm planning on studying some pics of the planets in the SOL system to see what some of the features might look like, but I want to try to do relatively random planets with different colors and such. Would you have some good resources for me to check out?

 

Questions:

Terminator: Would a terminator have a sharp edge or more gradual like I drew it? Also, would it typically be a nice circular arc?

 

Clouds/dust: I had originally tried to create "clouds", but I've had a couple people say they were dust. What would have to be done to make them look more like clouds?

 

Albedo features: What are you looking at? I do know what those are.

 

Aurorae: Can you show me a pic of what they may look like?

 

Thanks again for the critique, and I'm going to try to use everything you suggest to make the planets I create more "real".

 

Oh, what about the star field and "purplish cloud" in the background.

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Susano Grand Master

Susano

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Re: "Neat" Pictures

 

VERY COOL!!! Thanks Cancer!! I'm going to try my hand at creating some additional planets, and I'm planning on studying some pics of the planets in the SOL system to see what some of the features might look like, but I want to try to do relatively random planets with different colors and such. Would you have some good resources for me to check out?

 

Questions:

Terminator: Would a terminator have a sharp edge or more gradual like I drew it? Also, would it typically be a nice circular arc?

 

Unless the planet has massive terrain features, a nice circular arc.

 

Aurorae: Can you show me a pic of what they may look like?

 

aurora.jpg

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Cancer Grand Master

Cancer

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Re: "Neat" Pictures

 

VERY COOL!!! Thanks Cancer!! I'm going to try my hand at creating some additional planets' date=' and I'm planning on studying some pics of the planets in the SOL system to see what some of the features might look like, but I want to try to do relatively random planets with different colors and such. Would you have some good resources for me to check out?[/quote']

Probably the easiest thing to do is go to NASA Photojournal (http://photojournal.jpl.nasa.gov/index.html) and eyeball images.

 

For instance, http://photojournal.jpl.nasa.gov/catalog/PIA00058 (Neptune) shows the effect of high clouds near the terminator casting shadows into a deep atmosphere.

 

Questions:

Terminator: Would a terminator have a sharp edge or more gradual like I drew it? Also, would it typically be a nice circular arc?

 

The shape of the terminator is a pure geometry thing, depending on both the shape of the planet and your viewing angle. We get a decent sampling of terminator shapes from the Moon over the course of the month. Also, USNO has an "earth view" item at http://aa.usno.navy.mil/data/docs/earthview.html (see especially the notes section). For a spherical world, I think the terminator is always an arc of an ellipse. (I don't think it's an arc of a circle, but I'm not positive of that; I'd have to do or see the geometry proof.) For nonspherical worlds, it gets more complex. This is just a ray-tracing problem, and I suspect there's lots of design and art tools out there that can do this. A bunch of stuff at http://www.handprint.com/HP/WCL/tech27.html looks interesting in this regard. Just remember that for a planet the source of illumination is almost always effectively tiny (a point source) many, many object diameters away.

 

The terminator's "fuzziness" depends on atmosphere. The sharpness of the edge depends on the apparent size of the area it takes to go from mostly-lit to just-about-unlit. An airless rock may have a crinkled terminator because of mountains or other relief features (like the Moon does) but the edges will be sharp, because the edge between lit/unlit is microscopic (the surface of the rock). Something with a deep atmosphere can have a fuzzy, shaded terminator, because it may be many a good portion of the apparent size fo the planet's disk to go from top of the atmosphere (where it's still lit) to deep enough in the atmosphere that it's behind enough planetary matter that it's effectively unlit. (http://photojournal.jpl.nasa.gov/catalog/PIA08232 is a b/w, but it's a great one for showing this.) Also, if the atmosphere is layered by composition (different stuff is freezing out at different heights, as is true in Jupiter and Saturn) then the terminator may be colored, too, because of the layering.

 

Finally, the upper layers of an atmosphere will forward-scatter light. So if you're "behind" an object but looking back towards the sun, you may see a bright ring around the dark solid part of the planet. A nice b/w example (of Titan, which has a substantial haze layer high up) is http://photojournal.jpl.nasa.gov/catalog/PIA08219

 

Clouds/dust: I had originally tried to create "clouds", but I've had a couple people say they were dust. What would have to be done to make them look more like clouds?

 

My guess ... and this is little more than a guess ... is that we think of dust as producing more or less monotonic, very smooth patterns without much distinguishable structure, especially none in the azimuthal direction. Clouds have finer structure and patterns that aren't radial. Also, by the nature of what dust is, dust clouds are the same color as the surface of the planet. If it's a contrasting color, then it probably isn't dust. (The big exception here, of course, is dust from the low latitudes being blown up over polar ice caps.)

 

Albedo features: What are you looking at? I do know what those are.

 

"Albedo features" are brighter/darker areas on a planet. Calling them that avoids "prejudicial" labels, like calling the dark areas "maria" (as happened to the Moon) or dark streaks "canals" (as happened with Mars), that may make you look foolish later.

 

Aurorae: Can you show me a pic of what they may look like?

 

There's some interesting images of Earth's aurorae (seen from space) at http://www.nasa.gov/vision/earth/lookingatearth/dueling_auroras.html

 

Other worlds ... go to the NASA Photojournal page and search for "aurora". Just remember: aurorae are quite faint (so they show up only on the dark side, unless you have special spectral imaging tools, which for pictures as seen by people you wouldn't have), and the aurora mostly comes from the top of the atmosphere, where particles from space reach the planetary gas. Lower down and no particles reach the gas to cause it to glow; higher up and there's too few gas atoms to make perceptible emission of light.

 

Thanks again for the critique, and I'm going to try to use everything you suggest to make the planets I create more "real".

 

Wow. I am in no way an art student, but all I can suggest is study from life.

 

Oh, what about the star field and "purplish cloud" in the background.

I barely see the "purple cloud" (I had to tweak my monitor to see it), I have to admit. The stars are OK; there might be too many of them, considering how great the contrast is between a planet's surface and the dark background.

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Bazza Proficient

Bazza

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Re: "Neat" Pictures

 

VERY COOL!!! Thanks Cancer!! I'm going to try my hand at creating some additional planets' date=' and I'm planning on studying some pics of the planets in the SOL system to see what some of the features might look like, [/quote']I posted some on this page. Hope it helps. :)
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