Atmospheres

When I started this project, I didn't think I'd be spending much time simulating air, but here we are. My planets now have atmospheres:

I looked at a number of atmosphere shaders but couldn't find one that worked well with what I already had, so I wrote my own from scratch. As with most of what Undiscovered Worlds does, it aims for superficial believability rather than accuracy, but I think it looks reasonably decent. It doesn't actually calculate Rayleigh scattering and the like, but it pretends that it does. You can adjust atmospheric thickness, colour, specularity, etc. in the appearance settings.

The clouds are formed quite simply:

(1) Several fractal maps with different levels of detail are made and then combined. Then these are converted to the range -1 to +1, and then turned into their absolute values before being inverted. This gives the effect of wiggly lines. Finally, the resulting map is warped. This gives us the fairly large blobs of cloud with some stringy bits that you can see in the images.

(2) Then, another fractal map is made with a much smaller granularity. A map with larger granularity is used to remove large sections of this. This produces the smaller, puffier-looking areas of cloud.

(3) These two cloud maps are combined using yet another fractal, so that they merge into each other in a varying way.

(4) A simple swirl effect is added in places to give the effect of weather systems. Of course we make sure that these swirl in the correct direction, depending on hemisphere and overall planetary rotation direction.

(5) Clouds are removed in areas of low precipitation, to ensure that you don't get great big weather systems over deserts and the like.

Plus I've reduced the effect of the normal map, and made wetlands and large rivers visible (and specular) from space.

As always, it's not perfect, but I think it's looking reasonably decent. I shall probably continue to tinker with the clouds, but for now I'm happy to move on to the next bit, which will be some boring refactoring. I'm using a lot of three-dimensional vectors now, which are slow, resulting in annoyingly long planetary generation times. So I want to rewrite them all as one-dimensional ones to see if that speeds things up.

(Bonus shot: ocean worlds can now look quite dramatic:)