Space Art Week
The mention of space art or scenery conjures up, for most, images of ourselves free-floating out there in the darkness of space, with no ground or sky in sight obstructing any of the view. But just as common in the genre are scenes where there is a view from standing on the ground or flying high up but still within the atmosphere of a planet. Often the planet might not look much different from our own Earth. But how can a landscape that looks so earth-like still come across as actually being a different world altogether? A unique sky is often the main selling point to count on. This tutorial will show how regular looking landscapes, whether they're photographs or 3D scenes,can be transformed into far-out worlds that are imaginative but just as importantly - visually realistic in terms of how the cosmic elements blend into the existing scene.
Adding planets or other astronomical elements onto a dark outer-space background is fairly straightforward and rarely leads to unforgivable slip-ups even from those who are new to it. But making them visible through a daytime or otherwise well-lit sky can require a bit more thought to get it looking natural enough to convince the viewer. This guide assumes you already know how to make, or have access to the planets and landscapes and thus focuses more on successfully combining the two with three major steps to consider, no matter what kinds of planets/moons you're adding to what kind of scene.
Step 1: Blending modes:
In Photoshop, the layers in the layer palette have blending modes, which by default are set to "normal". Changing this can have dramatic effects on how the elements on that layer react with the layers below it. The only one you really need for this guide is the mode called "screen". Any planets or other space elements should have their layers set to screen mode so the darker parts are automatically faded out and only the parts lighter than the surrounding sky are visible, just like in real life (take the daytime moon for example, the dark parts take on the colour of the sky and appear almost invisible) Here's an example of the difference a simple blending mode change can make, note the second is the result you'd actually want for a realistic look.
Alternatively, you can just make the whole landscape/background render/photo a layer itself and have it above all the planet/stars layers instead, along with a black background at the base of it all. Then the planets and stars can be made as you would in a normal space scene anyway while you have the landscape layer hidden while working on it. This might be more practical for when more than just planets are used in the space area since then the planet layers can all be left on "normal" blending mode, that way stars, galaxies or other planets behind them don't show through.
Either method is fine and generates the same end result if done right. But for both it's important to mask out or erase any parts of the space scene that would in real life be obscured by much closer elements such as clouds and solid objects.
Step 2: Lighting Direction:
"Screen mode" does wonders right off the bat for making a planet or stars blend into a sky realistically. But even knowing this there's still potential mistakes that can kill the sense of realism. Most notably yet often overlooked - lighting angle. This is about making sure the light direction or "phase" of the planets/moons matches up with the light direction on the scene below. Too often a scene lit from a sun off to the right will have planets carelessly being lit from the left, or behind. Looking at the scene elements themselves (mountains, trees, buildings - anything) can be a hint as to what phase and lighting angle should be chosen for the planets. If your landscape is being lit from the right, then so should your planets. This animation shows how the phases of planets or moons vary depending on where the sunlight is coming from.
The keen eye would have noticed that the closer the sun is to being within the frame, the less of the planets you can actually see. When a moon or planet appears near the sun in the same patch of sky - only a narrow crescent or "moon shape" of it will even show. If the sun is off to one side out of frame, about half the planet would be seen, and if the sun is behind the viewer, even more of the planet becomes visible again. This graphic shows several moons across a full 360 degree of sky, the first one appears full as it's directly opposite to the side of sky the sun is in, meaning it would be behind you if you were facing towards the sun. The ones nearer the sun show less and form thin crescent-shapes.
Night time scenery is a bit more free in how much or little of the planets remain lit up, and from what direction too. Just make sure the light direction is consistent through all of them if there's several moons involved. A full moon next to a half or crescent moon in the same scene just wouldn't make much sense. Stars should also never show through planets too, even including the dark parts of the planet not very visible. This mistake is very common among photo-manipulation especially where fantasy skies are done this way which gives the impression the moon is clear rather than a solid object.
Step 3: Atmospheric Effects:
The atmosphere can have interesting effects on things we look at through it, changing the colour or even visually warping the shape of the sun and moon as they pass through the lower extremities of it as they rise and set. Cold air laden with ice crystals can cause halos to appear around the sun and moon, polluted or dusty air can stain them deep reds and oranges. Even a normal sunny day can still have low-lying planets fade out slightly nearer the finishing touch that further make your planets/moons belong to the scene rather than just looking like they were pasted on there.
Using the liquify tool and perhaps even the transform > warp tool in Photoshop can give you the ability to "distort" planets (or suns) that lie close to the horizon. Not always necessary but can have a cool effect reminiscent of those extreme photographic closeups of sun/moon rises and sets (think of the classic "African Sunrise" scene). Exactly how to warp it is trial and error, but as a guide - generally the base of the suns or moons (just above the horizon) gets squashed flatter by this illusion while the rest stays fairly rounded.
Note the reddish glow seen on the above examples too, this is a product of the lower extremities of the atmosphere discolouring the light coming into it from the sun/moon, giving them that orange look as they're rising and setting. Replicating this is easy and gets dramatic results. Brush over the layers of the planets or moons with a large soft brush set to "multiply" blending mode and with orange as your colour, this will appear to "stain" them, repeat over again to make the effect more intense. Hint: the closer to the horizon you get, the more red this effect becomes.
Halos around planets can really sell the fact the scene you're showing is cold - which would happen a lot in this genre as many planets out there are cold. There's many ways to do this, one way is to make a new layer, put a somewhat thick horizontal line across it, then go to Filter > Distort > Polar Coordinates and when the window for that comes up, just choose the first of the two distort options. This will turn that line into a ring (if it's oval-shaped just use the transform tool to squash it back into a circle) then use Gaussian Blur also in the Filter category and blur it to the extent you want, creating a soft doughnut-like shape. All steps are shown here.
Afterwards, just set the halo layer to screen as well. The colour can be adjusted to match that of the planet if the planet or moon isn't the typical white/grey colour. Position it around the planets to create the halo effect.
Conclusion: As mentioned at the beginning, this was a guide to help integrate planets into an existing photo-based or 3D rendered landscape for those epic sci-fi or fantasy scenes in the most true-to-life way possible. These rules aren't set in place by some higher art community working in the genre - they are based on real-life observations of how our own moon changes appearance at various times of the day in various atmospheric situations, ultimately - to make distant planets and extra moons look like they're really there in your scene - you want to try and emulate this as close as possible to get all the atmosphere and lighting dynamics true to life for a convincing result. For more artistic or stylized looking scenes though - well, rules were made to be broken!