Streaks Across My Procedurally Generated Terrain

Unity Engine
,
1

So I’m generating a height map via code with Perlin Noise and the applying it to terrains, but I’m getting these slightly streaks across the terrain.

8460467--1123271--terrain streaks.png
8460467--1123271--terrain streaks.png809×547 669 KB

I don’t mind posting my code up if anyone wants to see it, but it’s a lot and I’m just not sure where this might be taking place so I was hoping someone might have seen something like this before and have some advice on where to look.

Like I said; I’m generating the terrain by first creating a perlin noise map into a 2D array. Then I’m applying those heights using the terrainData.SetHeights method.

I’m also generating the noise map on a plane and the streaks seem to be missing there, so it’s something that’s happening somewhere when I’m setting the heights to the mesh.

2

Can you write the height map into an image and check if the streaks are already present?

3

The texture looks normal, so the streaks seem to be happening during the terrain shaping.

4

Do a simple cheesy 2x2 gaussian blur on the heightmap data before writing it… does the banding go away?

5

How would I do that? Using a shader? Or is there a way to blur/blend the actual height map values?

6

Just loop in 2 dimensions and do it… it’s just test code you’re going to throw away.

for (int y = 0; y < height - 1; y++)
{
  for (int x = 0; x < width - 1; x++)
  {
     float total = getCell( x, y) +
                  getCell( x + 1, y) +
                  getCell( x + 1, y + 1) +
                  getCell( x, y + 1);
     total /= 4;
     // todo: write this total to a fresh array (NOT THE SAME ARRAY!)
  }
}

(Obviously the “getCell()” method is based on however you’re storing this 2d float array.)

1 Like
7

The only point of trying this is to isolate where the regular ridged noise is coming from: is it a terrain bug or does your data actually contain this noise?

8

So it looks like I’m still getting the streaks on the terrain. Here is a look at what I did:

int width = 1 + terrainSO.AlphaMapResolution * 2 * worldLength;
        int height = 1 + terrainSO.AlphaMapResolution * 2 * worldLength;
        float[,] noiseMap = NewNoiseMap(width, height, seed, noiseScale,
            octaves, persistance, lacunarity, offset);
        DrawMesh(noiseMap, meshHeightMultiplier, meshHeightCurve);

        float[,] newArray = new float[noiseMap.GetLength(0) - 1, noiseMap.GetLength(1) - 1];

        for (int x = 0; x < noiseMap.GetLength(0) - 1; x++)
        {
            for (int y = 0; y < noiseMap.GetLength(1) - 1; y++)
            {
                float total = noiseMap[x, y] +
                    noiseMap[x + 1, y] +
                    noiseMap[x + 1, y + 1] +
                    noiseMap[x, y + 1];

                total /= 4;
                newArray[x, y] = total;
            }
        }

        for (int x = 0; x < noiseMap.GetLength(0) - 1; x++)
        {
            for (int y = 0; y < noiseMap.GetLength(1) - 1; y++)
            {
                noiseMap[x, y] = newArray[x, y];
            }
        }

This is the code leading up to actually setting the heights of the terrain, where I’m creating the noiseMap array.

And here is the code setting the heights:

for (int x = 0; x < terrainSO.Terrains.GetLength(0); x++)
        {
            for (int z = 0; z < terrainSO.Terrains.GetLength(1); z++)
            {
                int xStart = terrainSO.AlphaMapResolution * 2 * x;
                int xEnd = 1 + terrainSO.AlphaMapResolution * 2 * (x + 1);
                int zStart = terrainSO.AlphaMapResolution * 2 * z;
                int zEnd = 1 + terrainSO.AlphaMapResolution * 2 * (z + 1);
                terrainSO.Terrains[x, z].terrainData.SetHeights(0, 0, NoiseMapFragment(noiseMap, worldLength,
                    xStart, xEnd, zStart, zEnd));
            }
        }

There are a few methods there I’m not showing, let me know if it would be helpful to see any of them and I can post them. Really stumped with this!

9

To my eyes it almost looks like the distortion texture is squished. As in the X Y scale values are not the same to make a square texture.

what if you apply the same distortion to an imported subdivided grid plane?
could rule-out anything to do with terrane

10

Sorry not sure I’m following you. Not sure why X and Y wouldn’t be the same. I’ll see if I can try the grid plane idea though