How do I use Terrain SetHeights and GetHeights

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1

I have a small scene, consisting of a 128x128x128 terrain. Those are the dimensions and height. All I want to do is be able to modify the terrain height in a sensible and clear way.

I execute this code, every time you press “T”.

// Get the height at 0,0
float height = Terrain.activeTerrain.terrainData.GetHeight(0, 0);

Debug.Log(height);

// Increase it by .001

Terrain.activeTerrain.terrainData.SetHeights(0,0,new[,]{{height + 0.001f}});

// Print the new height
height = Terrain.activeTerrain.terrainData.GetHeight(0, 0);
Debug.Log(height);

Here is the debug output for the first height increase:

0 (the initial height, which is correct)

0.1289141 (? I increased it by .001…)???

The second time I do this, I get:

.1289141 ok correct, I guess…that was the previous value

16.62992 -??? What the heck!? How/WHY did it jump from .128 to 16.62

The unity documentation is pretty much useless on this matter.
If my terrain height has a max height of 100 meters, I should be able to increase the height at a given point by 0.01 to raise it a meter, right? Is the height increase being treated as a multiplier??

Can someone shed some light on this situation?

3 Answers

3
3

It’s quite simple. I’ve done a small test like you did. This are the results:

  • GetHeight returns the height value in the range [0.0f, Terrain Height]
  • GetHeights returns the height values in the range of [0.0f,1.0f]
  • SetHeights expect the height values in the range of [0.0f,1.0f].

So when using GetHeight you have to manually divide the value by the Terrain.activeTerrain.terrainData.size.y which is the configured height (“Terrain Height”) of the terrain.

The behaviour of GetHeight seems a bit strange and does not return what you would expect. This might be a bug / might be a feature, however without a proper documentation it’s more likely a bug.

This explanation makes sense (unlike the API implementation). And even more bizarre...there is no SetHeight function to match GetHeight.

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This was my experience too. From a terrain with height of 200: GetHeight: 62.65641 GetHeights: 0.3132821 (normalized, or same as if terrain height was 1) 0.3132821 * 200 = 62.65641

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2

Heights are actually stored as 16-bit integers; not sure why they decided to use floats for GetHeights/SetHeights, since there’s a conversion process when reading and writing.

Interesting. In working with this, it appears GetHeights returns the actual world height, but SetHeights expects a percent of the height (which as you said, gets stored as in int). I'll have to work out the math and confirm this :)

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No, GetHeights returns heightmap values. Those are unrelated to world height. It's not a percentage, rather it's a value ranging from 0-65535 (represented as a float from 0-1).

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This is what confuses me. In my original post, GetHeights() reported the height at 0,0 as 0. So I increased it by .001. When I checked the value after that, GetHeights reported .128xxxx. Weird. So I increase it by .001 again. The next time I checked the value it was 16.xxxx. This is why it seems like GetHeights reports world height.

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As I mentioned, the actual values are 16-bit integers. If you store .001, you're not going to get .001 back, you're going to get whatever the closest 16-bit integer equivalent is.

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4

SO AFTER SOME DIGGING and seeing this solution called simple! I got this snip working… here how I fixed my misconceptions!!
I was importing via 3rd party brush so scale is hard to tell at the moment my problem was I set the scale/Resolution after setting terrainData.size this scaled along the x z axis and looked flat

            TerrainData _TerrainData = new TerrainData();
            TerrainObj.transform.position = JsonUtility.FromJson<NVector3>(weaponDatabase.position).V3();
            
            _TerrainData.heightmapResolution = weaponDatabase.scale;
            _TerrainData.baseMapResolution = 64;
            Debug.Log("height scale");
            Debug.Log(_TerrainData.heightmapScale);// = 1000;
           // _TerrainData. = new Vector3(2,1000,2);
            Debug.Log(_TerrainData.size.y);
            _TerrainData.SetDetailResolution(2049, 2049);
            float[,] heighty = { { 1.0f, 0.23f }, { 0.10f, 0.40f } };
            _TerrainData.SetHeights(0, 0, heighty);
            _TerrainData.size = new Vector3(4000, 1000, 4000);