I'm deliberately writing this before 3am so that my posts will be more comprehensible and comprehensive than last night's.
First up, new screenshots:
Nothing big has changed since the last post, but a couple of things worth mentioning. First off my tangent normal calculation was wrong, which lead to all the normals being the wrong way around. It's kind of subtle the way the shadows were before, but I eventually realised that all the land looked like it was dipped in, and after a bit of hunting I realised my tangent vector was backwards.
I also switched to a 'night time' texture which doesn't include the aurora borealis. I didn't like how it looked, I preferred a clean texture. If anything I'd render that in myself afterwards, but I think that's kind of overkill for what I need.
I added specularity too, you can see it in the second screenshot. I pass in the gloss map/specularity map of the earth in on the alpha channel of the normal map, so that I don't waste another texture unit. I'm already wondering if there's a way I can avoid having the night and day textures, but I don't think I can at the moment. When I generate it myself, I should be able to again use the alpha channel of the 'day' texture simply as a luminosity channel to indicate where the lights are, and simply hard code them as white - that should suffice. In fact, I might be able to do that right now. Hmmmm...
Next up is atmosphere rendering. I'm going to read Nishita, then possibly O'Neil for clarification.
Outside of this hobby project, I somehow managed to swing myself an internship this summer at a game developer working on PS3 titles, so that should be pretty fun. I've no idea how much I'll be able to post about it, but hopefully I should have some cool stories to share.
EDIT: hey look at that, I did clouds. That was suspiciously easy. Still only using 3 texture units though, one for diffuse map (with night texture packed in alpha), one for normal map (with gloss map packed in alpha) and one for clouds, which could easily go in an alpha itself if I need another RGB tex down the line.