4 ms·

Planet Generation - Part I

77 points by marcacohen 12y ago

arethuza 12y ago
I wonder if anyone has generated planets by running a geological simulation - plates, subduction zones, vulcanism, erosion.... etc.
- QuadDamaged 12y ago
  Dwarf Fortress does.
  - gabemart 12y ago
    Does DF actually generate the geology of the whole planet, rather than just the playable area?
    - jonnycowboy 12y ago
      The entire planet!
    - golergka 12y ago
      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.
      - zalzane 12y ago
        plate tectonics is a planned feature for worldgen in the future
  - VikingCoder 12y ago
    This is the "Simpsons Did It" of video games.
  - pavel_lishin 12y ago
    Having used a few cheat codes to instantly see what every voxel is composed of... the generation isn't great. It's just spheres of certain materials, as well as x-shaped veins. It feels natural when you're randomly chipping it out, but when the curtain gets pulled back, it's not as impressive.
- jengamaster 12y ago
  That would be interesting. I had a quick look and found this paper, they simulate tectonic plate movement for terrain generation: http://www.cs.rpi.edu/~cutler/classes/advancedgraphics/S13/final_projects/benedetti_minto.pdf http://www.cs.rpi.edu/~cutler/classes/advancedgraphics/S13/f... and this one looks like some sort of terrain generation based on erosion: http://arches.liris.cnrs.fr/publications/articles/SIGGRAPH2013_PCG_Terrain.pdf http://arches.liris.cnrs.fr/publications/articles/SIGGRAPH20...
  - arethuza 12y ago
    Actually, it just occurred to me that what would be really cool would be a geology version of the Star Walk app - you point it at the ground/hill/mountain and it shows you what its made up of. Explaining the history of features would be even cooler :-)
    - augustl 12y ago
      And imagine if you had a game that generated terrain by erosion + tectonic plate movement, and you got to see a visualisation of that as it was generating :) 2 billion years of geological activity, simulated in a minute-scale.
      - mkesper 12y ago
        42!
- VikingCoder 12y ago
  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.
- livingparadox 12y ago
  I wondered the same thing a while ago, wanting to do so for my own purposes. I found this a while back. http://www.gamedev.net/topic/623145-terrain-generation-with-plate-tectonics/ http://www.gamedev.net/topic/623145-terrain-generation-with-... I'm hoping to find time to use it myself, and possible extend it. Thankfully its open source.
jengamaster 12y ago
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.
- shanee 12y ago
  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 :)
  - jengamaster 12y ago
    Ahh, I get it. Took me a couple reads of the code to see what was going on, but that is pretty cool. Thanks for the info!
- mrsharpoblunto 12y ago
  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 http://imgur.com/rpKalpk I've got a bunch of other procedural content generation blog entries over at http://www.junkship.net http://www.junkship.net, including this entry http://www.junkship.net/News/2011/11/13/building-steam-with-a-grain-of-salt http://www.junkship.net/News/2011/11/13/building-steam-with-... which covers a lot of similar ground to the parent article.
  - jengamaster 12y ago
    That's an impressive result! My worry was that it would become more obvious if I were to skimp on the poly count of the shape. Doesn't seem to have been an issue for you. Thanks for the links, I'll definitely check them out.
adolgert 12y ago
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.
- exDM69 12y ago
  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.
petenixey 12y ago
Shanee, I saw this and was immediately trying to figure out how I could email it to you. Then I saw the URL :) Nice work getting it on HN!
- shanee 12y ago
  Ha! Nice to meet you here :)
mrjj 12y ago
How to draw the owl...
murbard2 12y ago
One approach that you might want to try is to generate the planet using spherical harmonics. If you draw random coefficients for those harmonics, their distribution (in particular their rate of decay) will dictate how "coarse" the terrain looks. Edit: scratch that, you need an ungodly amount of parameters to get anything fine... works better for designing asteroids

77 points by marcacohen 12y ago

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

QuadDamaged 12y ago
Dwarf Fortress does.
- gabemart 12y ago
  Does DF actually generate the geology of the whole planet, rather than just the playable area?
  - jonnycowboy 12y ago
    The entire planet!
  - golergka 12y ago
    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.
    - zalzane 12y ago
      plate tectonics is a planned feature for worldgen in the future
- VikingCoder 12y ago
  This is the "Simpsons Did It" of video games.
- pavel_lishin 12y ago
  Having used a few cheat codes to instantly see what every voxel is composed of... the generation isn't great. It's just spheres of certain materials, as well as x-shaped veins. It feels natural when you're randomly chipping it out, but when the curtain gets pulled back, it's not as impressive.
jengamaster 12y ago
That would be interesting. I had a quick look and found this paper, they simulate tectonic plate movement for terrain generation: http://www.cs.rpi.edu/~cutler/classes/advancedgraphics/S13/final_projects/benedetti_minto.pdf http://www.cs.rpi.edu/~cutler/classes/advancedgraphics/S13/f... and this one looks like some sort of terrain generation based on erosion: http://arches.liris.cnrs.fr/publications/articles/SIGGRAPH2013_PCG_Terrain.pdf http://arches.liris.cnrs.fr/publications/articles/SIGGRAPH20...
- arethuza 12y ago
  Actually, it just occurred to me that what would be really cool would be a geology version of the Star Walk app - you point it at the ground/hill/mountain and it shows you what its made up of. Explaining the history of features would be even cooler :-)
  - augustl 12y ago
    And imagine if you had a game that generated terrain by erosion + tectonic plate movement, and you got to see a visualisation of that as it was generating :) 2 billion years of geological activity, simulated in a minute-scale.
    - mkesper 12y ago
      42!
VikingCoder 12y ago
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.
livingparadox 12y ago
I wondered the same thing a while ago, wanting to do so for my own purposes. I found this a while back. http://www.gamedev.net/topic/623145-terrain-generation-with-plate-tectonics/ http://www.gamedev.net/topic/623145-terrain-generation-with-... I'm hoping to find time to use it myself, and possible extend it. Thankfully its open source.

jengamaster 12y ago

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.

shanee 12y ago
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 :)
- jengamaster 12y ago
  Ahh, I get it. Took me a couple reads of the code to see what was going on, but that is pretty cool. Thanks for the info!
mrsharpoblunto 12y ago
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 http://imgur.com/rpKalpk I've got a bunch of other procedural content generation blog entries over at http://www.junkship.net http://www.junkship.net, including this entry http://www.junkship.net/News/2011/11/13/building-steam-with-a-grain-of-salt http://www.junkship.net/News/2011/11/13/building-steam-with-... which covers a lot of similar ground to the parent article.
- jengamaster 12y ago
  That's an impressive result! My worry was that it would become more obvious if I were to skimp on the poly count of the shape. Doesn't seem to have been an issue for you. Thanks for the links, I'll definitely check them out.

adolgert 12y ago

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.

exDM69 12y ago
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.

petenixey 12y ago

Shanee, I saw this and was immediately trying to figure out how I could email it to you. Then I saw the URL :) Nice work getting it on HN!

shanee 12y ago
Ha! Nice to meet you here :)

mrjj 12y ago

How to draw the owl...

murbard2 12y ago

One approach that you might want to try is to generate the planet using spherical harmonics. If you draw random coefficients for those harmonics, their distribution (in particular their rate of decay) will dictate how "coarse" the terrain looks. Edit: scratch that, you need an ungodly amount of parameters to get anything fine... works better for designing asteroids