How to procedurally generate a super simple terrain

Questions & Answers
1

Hey guys,

I’m trying to make a super simple terrain (two flat levels, and a flat cliff separating them). After a little bit of research I decided that a heightmap created at runtime would be the most efficient way to achieve this. It would need to have only two colors, and divided right through the middle (with a few curves). Incase I’m not explaining this very well, here is an example of what I’m trying to explain.

This picture is from the game Animal Crossing

The picture is from a game that I’m remaking, so please pardon the little houses and such.

Anyway, I really need some help figuring this out, so if anyone knows any good tutorials, or has any experience in this, please don’t be hesitant to share your knowledge!

-Thanks for all your help and comments! Gibson

2

Runtime terrain is actually not so hard now that Unity have made the properties available to the public.

Check out http://unity3d.com/support/documentation/ScriptReference/TerrainData.html - this is the object you’ll be playing with to create your terrain.

Your Terrain object has a single terrainData member that you can access to make changes.

TerrainData.GetHeights and TerrainData.SetHeights are used to set the height for sections of your map. The heights are stored as a 2-dimensional array of floats.

float[,] HeightMap = MyTerrain.terrainData.GetHeights();

The terrain is broken into a grid (the height and width of the grid are attributes of the TerrainData) and there is a height recorded at each point. So HeightMap[0,0] will be the height of the terrain in the top-left corner. HeightMap[2,4] will be 3 points across and 5 points down.

To randomise your terrain, simply fill an array with random values. But if you do this, you may be best off by then smoothing your values by averaging them with each-other, otherwise you can end up with a very spiky terrain.

//This example shows how to flatten your entire terrain to a height of 20...

   TerrainData TD = MyTerrain.terrainData;
   float[,] HeightMap = new float[TD.heightmapWidth,TD.heightmapHeight];
   for(int x=0;x<TD.heightmapWidth;x++)
   {
      for(int y=0;y<TD.heightmapHeight;y++)
      {
          HeightMap[x,y] = 20;
      }
   }

   TD.SetHeights(0,0,HeightMap);

Now, you can also do the same sort of thing with the various TEXTURES for your game world, using the AlphaMaps properties of your TerrainData.

This follows a similar pattern, but it’s a THREE dimensional array - one dimension is your x-coordinate, one is your y-coordinate, the last is the zero-based index of the textures you’ve added to your terrain.

So let’s say you have two different textures on your terrain - sand (#1) and grass (#2).

After you’ve generated your height map, you can then go through and apply textures based on the height - making lower sections sand and upper sections grass.

TerrainTextures[x,y,0] = 0.75f;
TerrainTextures[x,y,1] = 0.25f;

This would make point x,y 3/4 sand, with 1/4 of the grass texture coming through. You MUST normalise these values (ie. make sure they add up to 1).

Then use SetAlphamaps(0,0,TerrainTextures); to set it.