A Better Planet Tutorial

Okay, first of all - thanks for great tutorial... I'm relatively new to using any image editing program, and actually I haven't really used anything but ages old Paint Shop Pro 4.10, and recently GIMP. So I do not perhaps know what function or tool could be best suited for different situations, and what more, I'm using Finnish edition of GIMP so there is sometimes a bit of confusion with English terms for Filters and other tools... But whatever.

I did some experimenting with the instructions in this tutorial and I think I noticed something that hasn't yet been used, at least in this particular thread - I have no illusions that no one would have yet discovered this technique, but I figured I would share it none the less.

So, first of all a few things about shadows.

The shadow line (terminator) must always divide the sphere in two halves, though the line doesn't need to be sharp, as it never really is, except if the light source is a dot and there is no atmosphere.

This means that where ever the planet is looked, the shadow's start points (at the edges of the visible half of the planet) are always on opposite sides of the planet. What the shadow is shaped between them depends on the location of the light source. Here's a little picture to clarify:

Posted Image

The circle is the half of the planet facing towards viewer. The curved line is one possible shadow line, but all the possible shadow lines go through the crossed points on the opposite sides of the sphere. Or at least they should go very near them, little variation is never bad thing because there might be higher ground, clouds higher in the atmosphere and other stuff to make the sphere not-so-spherical. However, the rule demonstrated in the picture can be applied to all (nearly) spherical objects in a system with (nearly) dot-type light source.

Second thing I noticed that this tutorial does not cover oceans or other stuff like that. And oceans are a crucially important aspect of any Earth-like planet, so this guide doesn't get one very far to that. Granted, it gives ideas and techniques but I eventually had to come up with putting sea to surface layer by myself. One possibility is this - get the greenish surface layer and put it on top of blue background colour. Then make black the transparent colour of the green terrain layer and adjust its colours until you have some nice green/brown continents and islands on water background.

Other possibility is to import a map of some real/fictional planet's surface, resize the layer into a square of, say, 3000x3000 and then map the imported terrain into sphere... this works pretty well too.

Third thing - bump mapping is very important.

Not only for terrain, but also the cloud layer greatly improves by bump mapping it. After all, the clouds cast shadows like anything else...

Fourth - it's good to have at least two separate cloud layers. That makes the cloud system more interesting. Also, it might be necessary to just use Normal layer setting and make black transparent colour of the cloud layer(s); multiple cloud layers on Hard Light mode tend to darken the places with black areas a little too much.

Fifth - the highlighted edge of the planet is not really good looking in all cases. IMO it drowns a lot of detail and doesn't really look that real. It would be different if the sun was behind the planet, ie. just rising/setting... Then it would lit up the eatmosphere like a christmas tree.

Well, these are just my notes on the subject. I wouldn't have started making these experiments without this guide, so Kudos to Marvin x...

And finally, here are some of my results of experimentation. First one is some random planet created more or less along the lines of this guide, second one adds some more of mentioned changes, and the last is obviously Earth. I used THIS as basis for the Earththingy, it turned out quite well in my opinion...

First try...

LINK to high-res version Posted Image