How to make procedurally generated terrain look realistic

Question

I generated a terrain using a technique from this blog post, everything worked well and I got the wanted result. This is what my generated island looks like:

As you can see the terrain have a polygon structure. Here is the graph that generated this mesh:

This is the code used to generate this mesh from the graph:

    void DrawPolygons(){
    List<Vector3> vertices = new List<Vector3>();
    List<int> triangles=new List<int>();
    List<Color32> colors = new List<Color32>();

    foreach(Center c in centers){
        float zp = zScale*c.elevation;
        vertices.Add(new Vector3(((Vector2)c.point).x,zp,((Vector2)c.point).y));
        Color c0 = getColor(c);
        colors.Add(c0);
        int centerIndex=vertices.Count-1;
        var edges = c.borders;
        int lastIndex = 0;
        int firstIndex = 0;

        for(int i =0;i<c.borders.Count;i++){
            if(edges[i].v0 == null && edges[i].v1 == null)
                break;

            //get voronoi edge
            Corner corner0 = edges[i].v0;
            Corner corner1 = edges[i].v1;

            //get vertices height
            float z0 = zScale*corner0.elevation;
            float z1 = zScale*corner1.elevation;

            //add color
            if(edges[i].river>0){
                c0 = Color.cyan;
            }else{
                c0 = getColor(c);
            }

            colors.Add(c0);
            colors.Add(c0);

            //creat voronoi edge points
            Vector3 v0 = new Vector3(((Vector2)corner0.point).x,z0,((Vector2)corner0.point).y);
            Vector3 v1 = new Vector3(((Vector2)corner1.point).x,z1,((Vector2)corner1.point).y);

            //add points to vertices
            vertices.Add(v0);
            var i2 = vertices.Count - 1;
            vertices.Add(v1);
            var i3 = vertices.Count - 1;

            //add triangles calculating surface normals so i can always add triangles clockwise correctly
            var surfaceNormal = Vector3.Cross (v0-(new Vector3(((Vector2)c.point).x,zp,((Vector2)c.point).y)), v1-(new Vector3(((Vector2)c.point).x,zp,((Vector2)c.point).y)));
            if(surfaceNormal.y>0)
                AddTriangle(triangles, centerIndex, i2, i3);
            else
                AddTriangle(triangles, centerIndex, i3, i2);

            firstIndex = i2;
            lastIndex = i3;
        }
    }

    //calculating uv's
    Vector2[] uvs = new Vector2[vertices.Count];
    for (int i = 0; i < uvs.Length; i++)
    {
        uvs[i] = new Vector2(vertices[i].x / SIZE, vertices[i].z / SIZE);
    }

    mesh.Clear();
    mesh.vertices = vertices.ToArray();
    mesh.triangles = triangles.ToArray();
    mesh.uv = uvs;
    mesh.colors32 = colors.ToArray();
    mesh.RecalculateNormals();
    mesh.RecalculateBounds();
    meshFilter.sharedMesh = mesh;
    meshCollider.sharedMesh = mesh;

}

I would like to know if it's possible to have a noisy/realistic looking terrain from this. How would I implement such a thing?

Basically I want something with no hard edges, terrain that looks smooth but not too smooth, something like this video shows:

Answer 1

First of all, note that Unity already has a very nice terrain system out-of-the-box. It gives you a lot of nice features for free like LOD, occlusion culling and a lot more. Also, it can look pretty neat. You can still generate terrain procedurally, but the input data it expects isn't a mesh but a height map in form of a two-dimensional array of floats. So if you want to keep using that cell-based algorithm, you will have to convert it to output a heightmap instead of a list of vertices.

But no matter which technical implementation you choose to render your map: If you want to generate a landscape which combines discernible large features with small details, then it is usually a good idea to layer multiple terrain generation algorithms on top of each other. Use a pass with a high amplitude and a low resolution to generate the basic shapes (like you already do), and then run another pass with a lower amplitude but a higher resolution to create detail.

You could, for example, apply the same algorithm you are already using again for each cell to subdivide it further. Or you could use a completely different algorithm to "rough up" each cell like Perlin Noise.

Also, don't underestimate the effect of good textures. A high-resolution texture with a good normal map could make a terrain surface look a lot less plastic-like. Keep in mind that you need to also call mesh.RecalculateTangents() on your mesh for normal maps to render correctly.

I am looking forward to exploring the procedurally generated worlds in your game.

Answer 2

A good way to generate realistic terrain is to simulate physical processes like

• corrosion
  • either with a "uniform" corrosion algorithm or simulation of water or both
• simulation of interaction of multiple sediment layers, don't forget that the origin of a lot of amazing landscapes are the sediments and the interactions of them with water underneath, like stone, dirt, sand, etc.
• plate tectonics(?) (no idea which game simulates that but it's maybe possible)