5 ms·

Build A Terrain Engine For Video Game Development

45 points by felipemnoa 15y ago

usedtolurk 15y ago
What a great tutorial - explained just enough to leave me desperately wanting to try it myself. 5 years on, but I'd guess it's still relevant to mobile devices. Anyone know if there are better accepted approaches now?
- exDM69 15y ago
  Height maps are still the way to go for terrain. The rendering methods themselves have changed but the basic idea remains the same. These days you tend to push big blocks of geometry to the GPU while a decade ago it was common that the terrain would get generated triangle by triangle every frame to minimize the amount of geometry.
  - iwwr 15y ago
    How would you model concave terrain or terrain with "holes" (like erosion arches or caves)?
    - JoeAltmaier 15y ago
      Not that way.
    - levesque 15y ago
      For what I know that's still a challenge for developers, they most often seem to make two distinct types of area: -Outdoors, where there are no concavities in the landscape and elevation models are used. -And indoors, where you use a different type of modeling, last time I checked binary space trees were pretty common.
      - jheriko 15y ago
        fyi the reason for using a BSP is to get a "cell-portal graph" which allows visibility computations to be trivialised - the benefits of the BSP tree itself for, e.g. rendering with no overdraw are not very valuable. e.g. despite the hype otherwise this was never realised in Quake for zero-overdraw rendering, instead the PVS (based on the cell-portal graph) was used to result in "very little overdraw". This technique continues to be used today in every major game engine (id Tech 4 (maybe 5?), Source, UE3, CryEngine, numerous other proprietary engines).
    - NickPollard 15y ago
      The most common way is by having 'holes' defined in the mesh (ie. maybe use 1 bit for each point to determine whether it exists or not) and then creating extra geometry to attach to that. Alternatively, you can try a voxel-based approach and then use an algorithm like Marching-cubes to reconstruct a smooth mesh over the top of it. Or, you could change the heightmap data to also include X/Z displacement as well as Y displacement. This would allow some shallow caves and small overhangs, but nothing too crazy. There will be plenty of other methods you could use too, these are just a starting point.
    - stonemetal 15y ago
      Erosion arches tend to be non-terrain geometry. I have seen caves done several different ways. The first was use height maps, but mark certain areas as artist owned. Then give artist tools to modify terrain, so caves are 100% hand carved. The second is to generalize height maps. Heights always come in odd numbers, even numbers are always floors, and odd numbers are always ceilings(i.e height 0 is the ground, 1 is the cave roof, 2 is the cave floor.)
    - jheriko 15y ago
      If you use distance field based raytracing this "just falls out" by deforming the isosurface of the terrain appropriately (e.g. with noise). The downside of using noise to do this it that you get corresponding floating bits of terrain for the indentations - one solution is to start with some y = noise(x,z) then if y > 0 subtract a noise(x,y,z) from the value... Using polygons to solve this is highly nontrivial - despite the naive suggestions made already.
haasted 15y ago
Notch posted an article a while back on terrain generation in Minecraft. Short, but contains some interesting details. He unfortunately never seemed to get around to writing Part 2, though... http://notch.tumblr.com/post/3746989361/terrain-generation-part-1 http://notch.tumblr.com/post/3746989361/terrain-generation-p...
jheriko 15y ago
This is quite old but still vaguely impressive to see the visual results - however there is one fatal flaw, every newbie gamedev churns out a terrain engine because they look very good with little technical investment and are easy to implement in any tutorial copied rendering framework... in essence its teaching newbies how to do newbie stuff. I'm fairly convinced that distance field raytracing is the way to go for terrain rendering - one poly and some extra overhead in the fragment shader (which is not trivial I'll admit) vs. thousands/millions of polys and the same fragment shading pass you use for everything else...
- jheriko 15y ago
  (trying to undo the snobbery a little - I made a demo of something like this some 5 years ago and it actually helped land me a job)
- felipemnoa 15y ago
  >>I'm fairly convinced that distance field raytracing is the way to go for terrain rendering - one poly and some extra overhead in the fragment shader Could you elaborate a bit more on this technique. Can you use this technique in 3D games when playing real time? I had the impression that all 3D games used meshes for the terrain, do you know of a popular 3D game that uses this technique you mentioned? Finally, do you happen to know a link to a good introduction/tutorial? Thanks!
  - corysama 15y ago
    http://wwwcg.in.tum.de/Research/Publications/TerrainRayCasting http://wwwcg.in.tum.de/Research/Publications/TerrainRayCasti... Claims ~30fps @1080p on an Nvida 260GT (that's a reasonable gamer card today) Seems like a more formal reinvention of this guy's "Quadtree Displacement Mapping" http://www.drobot.org/ http://www.drobot.org/ You would be better to check out drobot's slides first. More descriptive, less formal.
    - felipemnoa 15y ago
      Thanks!

45 points by felipemnoa 15y ago

What a great tutorial - explained just enough to leave me desperately wanting to try it myself. 5 years on, but I'd guess it's still relevant to mobile devices. Anyone know if there are better accepted approaches now?

exDM69 15y ago
Height maps are still the way to go for terrain. The rendering methods themselves have changed but the basic idea remains the same. These days you tend to push big blocks of geometry to the GPU while a decade ago it was common that the terrain would get generated triangle by triangle every frame to minimize the amount of geometry.
- iwwr 15y ago
  How would you model concave terrain or terrain with "holes" (like erosion arches or caves)?
  - JoeAltmaier 15y ago
    Not that way.
  - levesque 15y ago
    For what I know that's still a challenge for developers, they most often seem to make two distinct types of area: -Outdoors, where there are no concavities in the landscape and elevation models are used. -And indoors, where you use a different type of modeling, last time I checked binary space trees were pretty common.
    - jheriko 15y ago
      fyi the reason for using a BSP is to get a "cell-portal graph" which allows visibility computations to be trivialised - the benefits of the BSP tree itself for, e.g. rendering with no overdraw are not very valuable. e.g. despite the hype otherwise this was never realised in Quake for zero-overdraw rendering, instead the PVS (based on the cell-portal graph) was used to result in "very little overdraw". This technique continues to be used today in every major game engine (id Tech 4 (maybe 5?), Source, UE3, CryEngine, numerous other proprietary engines).
  - NickPollard 15y ago
    The most common way is by having 'holes' defined in the mesh (ie. maybe use 1 bit for each point to determine whether it exists or not) and then creating extra geometry to attach to that. Alternatively, you can try a voxel-based approach and then use an algorithm like Marching-cubes to reconstruct a smooth mesh over the top of it. Or, you could change the heightmap data to also include X/Z displacement as well as Y displacement. This would allow some shallow caves and small overhangs, but nothing too crazy. There will be plenty of other methods you could use too, these are just a starting point.
  - stonemetal 15y ago
    Erosion arches tend to be non-terrain geometry. I have seen caves done several different ways. The first was use height maps, but mark certain areas as artist owned. Then give artist tools to modify terrain, so caves are 100% hand carved. The second is to generalize height maps. Heights always come in odd numbers, even numbers are always floors, and odd numbers are always ceilings(i.e height 0 is the ground, 1 is the cave roof, 2 is the cave floor.)
  - jheriko 15y ago
    If you use distance field based raytracing this "just falls out" by deforming the isosurface of the terrain appropriately (e.g. with noise). The downside of using noise to do this it that you get corresponding floating bits of terrain for the indentations - one solution is to start with some y = noise(x,z) then if y > 0 subtract a noise(x,y,z) from the value... Using polygons to solve this is highly nontrivial - despite the naive suggestions made already.

haasted 15y ago

Notch posted an article a while back on terrain generation in Minecraft. Short, but contains some interesting details. He unfortunately never seemed to get around to writing Part 2, though... http://notch.tumblr.com/post/3746989361/terrain-generation-part-1 http://notch.tumblr.com/post/3746989361/terrain-generation-p...

jheriko 15y ago

This is quite old but still vaguely impressive to see the visual results - however there is one fatal flaw, every newbie gamedev churns out a terrain engine because they look very good with little technical investment and are easy to implement in any tutorial copied rendering framework... in essence its teaching newbies how to do newbie stuff. I'm fairly convinced that distance field raytracing is the way to go for terrain rendering - one poly and some extra overhead in the fragment shader (which is not trivial I'll admit) vs. thousands/millions of polys and the same fragment shading pass you use for everything else...

jheriko 15y ago
(trying to undo the snobbery a little - I made a demo of something like this some 5 years ago and it actually helped land me a job)
felipemnoa 15y ago
>>I'm fairly convinced that distance field raytracing is the way to go for terrain rendering - one poly and some extra overhead in the fragment shader Could you elaborate a bit more on this technique. Can you use this technique in 3D games when playing real time? I had the impression that all 3D games used meshes for the terrain, do you know of a popular 3D game that uses this technique you mentioned? Finally, do you happen to know a link to a good introduction/tutorial? Thanks!
- corysama 15y ago
  http://wwwcg.in.tum.de/Research/Publications/TerrainRayCasting http://wwwcg.in.tum.de/Research/Publications/TerrainRayCasti... Claims ~30fps @1080p on an Nvida 260GT (that's a reasonable gamer card today) Seems like a more formal reinvention of this guy's "Quadtree Displacement Mapping" http://www.drobot.org/ http://www.drobot.org/ You would be better to check out drobot's slides first. More descriptive, less formal.
  - felipemnoa 15y ago
    Thanks!