Hi!

I have an idea for game about world building on planet Earth. Planet would be wiped clean with only sandy desert, snowy desert and oceans/seas. Everything else would be built as part of actual game-play. Have nice story in mind etc etc. I wont get too deep in all of that for now.
I have few things I need to clarify, since I am not personally experienced in this exact Procedural generation stuff.

1. I know there is (rather was) game called Fuel. Huge procedurally generated wold compared to most games. But what about planet sized world?

What I have in mind is something slightly similar to Google earth data (may be even could extract data from there). Only instead of high res images, have either image based (displacement maps) or other type of data for basic terrain generation that then gets detailed out with procedural generation.
So what it would take? How far the data can be compressed while not losing consistency. I would like to keep as much data as possible outside the gaming device.

Also there would be incoming data after initial world is built - terraforming, buildings, vegetation etc (this as much procedurally generated as possible too).

2. Which game engine would be suitable for something like this? Existing ones can handle it or need new engine?

P.S. If possible I would like to keep this to technological side, for now. I know it isn't the smallest project idea. How to do it... will figure it out later. Probably Indiegogo.

Game worlds are notoriously small, there's often only the illusion of a larger world. The level of detail is the real crux which will define if your project is possible, pain-ful or simply impossible. For a 1:1 generated world it would be simply the latter case.

What I was thinking with that detail problem was, if the basic terrain of Earth can be done by extracting data from Google earth and then auto-detailed with that procedural generating algoritm, then it should be fine. All it have to do is look reasonably similar to Earth. Any other specific changes would be made by players later.
Some glitches may occur and if it wouldn't be possible to fix with algoritms, them my idea would be to do pre-alpha events where peoples can take part in terraforming/fine detailing.
Basically making the game development part of game itself.
At lest that's the idea...

What is your team size? Budget?

True that as long as you CAN export existing terrain data, and spicing it up with some procedural generation, you might get away with less work than creating everything manually.

But really, the amount of work still needed to a) export and import ALL of earths terrain data (I hope you will leave away the oceans, and go without any underwater details ), and b) write and test procedural algorithms that can do the rest reliable, looking interesting and without introducing balancing problems is still staggering. The amount of testing to make sure there is no bug somewhere hidden in your virtual world might alone take a lot of time. Of course you can just setup the procedural part, test that this work and forget about the real geodata. With the real geodata, you introduce all kind of possibilities for bugs to happen.

There IS some precedence, AFAIK the team that has written No Mans Sky was actually about 10-15 people, working some years on the game. Pretty small for the scale the game COULD take on given you are happy with what the procedural generation spits out.

But you are still WAY outside of the amount of money you could reliably get from Indiegogo. You will most probably need another source of investment.

But leaving away the non-technological stuff.... I think you need to try it out yourself. You COULD look into how games like No Mans Sky have done it (AFAIK it was written from scratch), at some point you will need to do your own prototype. Just start with one US State and see how much time you need to get it running, and with that test how much data gets pushed over the network, how much the local machine is spinning and all of that.

Nobody will be able to tell you how to build this idea of yours because nobody was really mad enough to try this yet (some came close, or did even more like No Mans Sky, but minus the real geodata of course).

You guys are being a little pessimistic on the technical front. Sean O'Neil, Ysanaeya, myself, and a host of others have each bootstrapped realistic scale planet renderers in somewhere under a year, working solo. If you take the time to read the literature, it's not that complex of a problem.

There is of course a long tail in content creation - building the biome mapping, creating flora/fauna/greebles for each biome, etc. But that's really up to you how detailed and varied it needs to be, and hence how long it takes.

Of course, when you reach that point, you still have a huge empty world with no actual gameplay. And therein lies the sticker. What possible use for a game world so big it takes a year of real time just to walk around the circumference?

That might be true... but when you move from just procedural generation to mixing real geodata with procedural generation, wouldn't that make the project far more complex?

Especially as I read the TO idea to be as close to real earth as possible... thus a lot of testing will be needed so that procedural creation does not mess up the geodata.

But agreed, that part might be solvable in a year... or two. Nothing that is impossible to achieve.

I also think that the rest of the idea is where the thing falls flat on its face. An empty world without gameplay will hardly make people jump in excitment.

"Butbut it worked for Minecraft" - Because Minecraft actually has gameplay, no matter how light it might be. Minecraft invests a ton of work into their voxel creation system, which by itself might add another 6 months (maybe more) to create.

An empty world, no gameplay only works when your creation tools really rock. And these are an additional challenge altogether.

The answer to 1 and 2 is: outerra

Holy sh*t, I forgot about this engine!

You are right, that is pretty much most of the work done right there... looks like the engine has come a long way since I last looked at it many moons ago

Now, how to make anything meaningful with the empty world created....