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Planet Generation - Part I

shaneenishry.com

11–20 of 27 posts

Re: Planet Generation - Part I

#11

If you search for "fibonacci grid sphere," you'll find the grid used for research. It's less regular and a lot more work, with a few regions of five or seven sides, but it might look more natural, and it's used because it has fewer sharp corners than the icosohedron. Just another option.

Fibonacci grid spheres look really cool. But...

The surface geometry is not very important in this task. You can easily push out a million triangles or more, so you're going to get a pretty round shape in the end, no matter which primitive you take as a starting point.

The hard part is texturing and area distortions. Ideally you wouldn't have texture boundaries crossing the triangle boundaries. Since textures are rectangular, using the "cube sphere" is a very popular choice for planet rendering.

Things get more difficult if you have to use real-life imagery (satellite images and aerial photography), because then you're going to have to stitch several layers of textures on top of each other. There are texture splatting techniques and other tricks that need to be done to get proper texturing on the planet.

Re: Planet Generation - Part I

#13
post #6

Earlier quoted context omitted.

Dwarf Fortress does.

Does DF actually generate the geology of the whole planet, rather than just the playable area?

You select the area you'll be playing with at the embark, so yes, the whole planet's surface is generated. But I apart from the surface layer, I doubt that this simulation takes planet core into account, for example: in the game world's it would be filled with SPOILER anyway.

Re: Planet Generation - Part I

#15
post #6

Earlier quoted context omitted.

Does DF actually generate the geology of the whole planet, rather than just the playable area?

You select the area you'll be playing with at the embark, so yes, the whole planet's surface is generated. But I apart from the surface layer, I doubt that this simulation takes planet core into account, for example: in the game world's it would be filled with SPOILER anyway.

plate tectonics is a planned feature for worldgen in the future

Re: Planet Generation - Part I

#16

Very cool result! I've been wondering about applying the height-maps that you get from Perlin/Simplex directly to the vertices of a planet, for 3D terrain. I'd imagine that the cube mapping approach might not be perfect for this because of the irregular distance between vertices. The geodesic dome would probably work, but I have no idea how you would generate noise for a shape like that.

You'd actually generate noise just the same way as I used 3D Simplex noise.

I am unsure on UV mapping though as I have not experimented with it yet when using geodesics. Instead I just escaped the problem by using a collapsed cube :)

Re: Planet Generation - Part I

#19

Very cool result! I've been wondering about applying the height-maps that you get from Perlin/Simplex directly to the vertices of a planet, for 3D terrain. I'd imagine that the cube mapping approach might not be perfect for this because of the irregular distance between vertices. The geodesic dome would probably work, but I have no idea how you would generate noise for a shape like that.

I've used a cubemap approach to render procedurally generated asteroid geometry and it works pretty well. I start by generating the heightmap using 3D simplex noise, Then when rendering I use a domain shader to offset the vertices of an icosphere along the normal vector according the the height in the heightmap.

http://imgur.com/rpKalpk

I've got a bunch of other procedural content generation blog entries over at http://www.junkship.net, including this entry http://www.junkship.net/News/2011/11/13/building-steam-with-... which covers a lot of similar ground to the parent article.

Re: Planet Generation - Part I

#20
post #2

I wonder if anyone has generated planets by running a geological simulation - plates, subduction zones, vulcanism, erosion.... etc.

This is roughly the premise of the Neal Stephenson novel Reamde. There's a virtual world named T'Rain after the terrain generation algorithm used to create it.
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