# Random terrain generator

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Anyone know of a good algorithm for creating a descent looking random terrain. Ive made one once that uses pyramid like raising of the terrain functions and randomly drives over the terrain. Just wondering if anyone has any good ones he can recomend? -CProgrammer

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One of the Game Programming Gems books (I think #1) describes a technique called something like Fault Formation. Basically, you start with a flat map and proceed to draw random lines across it. Each time you draw a line you pick a side and either raise or lower all values on that side of the line. Draw enough lines, and you end up with a fairly decent terrain, but it's just a little too angular. If you run a blur filter across it to smooth out any rough edges it looks better.

I've adapted the algorithm before to also use circles. Draw a circle and either raise or lower the terrain inside of it. Circles can be useful, for example, in creating terrain that appears as if it has been impacted by asteroids or disrupted by vulcanism, especially if you 'seed' it with a few large circular depressions midway through, and run a few passes of shallower fault generation on top of the depressions.

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Thanks guys for the help.
These ideas sound great and easy to implement :D

-CProgrammer

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Another good equation i like is perlin noise, you may or may not want to look into it...

clicky
clicky

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This is a also a very good tutorial.
Robot-frog Terraintutorial

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I think I used all those links suggested so far, ended up using what I think is called the 'Hill' method. Basically you do this
for i = 1 to numHills
x=rand(between 0 and mapWidth)
y=rand(between 0 and mapHeight)
loop
There are many details you need to sort out here such as
• The hills are added to the current terrain heights which means with a decent number of hills (you need a few 100) you either need to make individual hills very shallow, or normalise the finished map to a given maxHeight to stop it being ridiculously steep everywhere
• The shape of hill ie a triangular cross-section, parabolic, sine curve etc
• The number of hills and the weighting each radius gets

• I get some quite attractive landscapes generated but the obvious disatvantage is it's all smooth curves. I tried a perlin noise approach but it was always really jagged. You get small bumps with a lot of hills since many are small if you tune it right, but to get pointy /jagged hills/outcrops as well as curves I'd suggest blending the 'hill' method with a more jagged approach, or allowing some hills to be created with jaggedness. Or you could create a jagged map and a smooth one and choose the highest values from each, giving jagged rocks coming out of a smooth landscape - most of the landscape is pretty smooth normally. Feel free to PM me if you want to chat about this...

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I really like midpoint displacement. It is simple and procedural. Also it is fractal/recursive, which makes it fairly easy to generate different levels of detail. There are tons of examples of this, but the basic idea is that you find the midpoint of a plane, then move that point up or down a random distance. You then have four new planes (the quadrants of the original plane), which you do the same thing to. You can repeat this as many times as you like, each time decreasing the random drift a little. Repeating even 4 or 5 times gives you some pretty slick terrain. The only problem with this approach is that it's hard to 'seed' the terrain - place rivers, mountains, etc where you want them.

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d000gh: Yeah thats not bad either. Thats pretty much the same as my initial method.

The perlin noise is also interesting. I also like fact that it can animate clouds. Not bad. Worth looking into.

-CProgrammer

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Hmm, interesting post on midpoint displacement. It shouldn't be too hard to program a vertex shader to do that in 3D in realtime if you feel like making earthquakes or something!

Mark
SFXEngine: Advanced Sound Effects Creation Software
http://www.sfxengine.com

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