Yes I know!
But if you're potentially outputting 60-100k maps, things start to runaway pretty quickly. But I guess it all depends on what realism you can squeeze into say 8 hrs. If you can do it in less, then all the better.
I hope that it at least gives you an insighht into what I see folks doing- at least with indie dev programs. I think most of them do use the software that I use, ie World Machine, GeoControl, Leveller, Wilbur, L3DT.
To give you some kind of idea of where the industry is at, I had contact from an enviroment artist who was working on GoW 4,and he was blown away by the pics of our terrain in Outerra- wanting to know how we did it. I was really shocked, because I didn't think what we were doing was anything advanced (apart from the goreffing bit). But on reflection I suppose it is really because most games don't require/give such large fovs on game levels and so don't require that level of realism, and Outerra is clearly unique and way ahead of the game in that department. The mountain ranges are a dead give away. In fact Outerra forced me to bite the bullet and develop a new approach. The only comparable terrains are in flight sims and they're almost always real earth data. So that gives us an insight into where the games industry is at regards terrain modelling. We're pretty much stuck right now.
I've been doing terraining as a hobby for maybe 10 years. I've beta tested most of the software I use. The single biggest barrier to moving procedural terrain modelling on from where we are now, is the creation of larger scale terrain features such as mountains ranges, continental divides and long rivers that connect mountains to plains to sea, and the like- basically geography. After a few years of trying out stuff and badgering devs about new tools
(especially regards mt ranges), I gave up using procedurals for the time being and switched to using real world data but manipulated in various programs.
So, you can see that not even the best enviroment artists are able to generate procedural terrain on these scales that looks even half way real because the tools just aren't there- so they have to use real earth data, like say they did in Crysis. My process is comparatively time consuming and I do it for the love of it, not to budget or deadlines. So there is definitely a niche there for you (a top down procedural solution for planets)- and one that will grow in the future with 100% certainty as engines like Outerra come online.
Another thing I've grown to realise over the years is that terrain consists of two sides of a coin: terrain and rivers. The importance of rivers are largely overlooked I find- no doubt because in small terrains you don't have to think whether the hydrology of a terrain make sense. So, really you'd need to combine the tectonic uplift with an erosion process. Ideally for an earth-like planet, you'd also have some intermittent glacial action too because that produces distinct features that no other process can.
There's a guy who programs a procedural terrain generator for gpu called Florian Bosch. We did talk a bit about what we saw as the problems needing to be solved. He's not really that passionate about terrain though-he has his finger in a lot of pies. He did suggested tectonics combined with a thin crust deformation (not fully volumetric).
http://codeflow.org/ Just read your chpt 6. Yes, the supercontinent cycle is really where it's at.The Caltech one looks easy to implement...haha...wow,
"With the new algorithms, the scientists were able to simulate global mantle flow and how it manifests as plate tectonics and the motion of individual faults. According to Stadler, the AMR algorithms reduced the size of the simulations by a factor of 5,000, permitting them to fit on fewer than 10,000 processors and run overnight"
Even they have to wait..had to smile at that
monks