diamond_square_algorithm

using System;
using System.Collections;
using System.Collections.Generic;

public class MidPointHeight
{
    public int Size { get; set; }
    public float FallOff { get; set; }
    public bool Wrap { get; set; }

    public int cSize { get; private set; }
    public float cDeviance { get; private set; }

    public static float cRange { get; set; }

    private Random rand;

    public float[,] heights { get; private set; }

    public MidPointHeight(int Seed, bool Wrap, float Range)
    {
        this.FallOff = 0.495f;
        this.rand = new Random(Seed != -1 ? Seed : (int)DateTime.UtcNow.Ticks);
        this.Wrap = Wrap;
        this.cSize = 2;
        this.cDeviance = 1.0f;
        cRange = Range;

        this.heights = new float[cSize, cSize];

        //init minium
        if (this.Wrap)
        {
            this.heights[0, 0] = this.rand.GetHeight();
            this.heights[0, 1] = this.heights[0, 0];
            this.heights[1, 0] = this.heights[0, 0];
            this.heights[1, 1] = this.heights[0, 0];
        }
        else
        {
            this.heights[0, 0] = this.rand.GetHeight();
            this.heights[0, 1] = this.rand.GetHeight();
            this.heights[1, 0] = this.rand.GetHeight();
            this.heights[1, 1] = this.rand.GetHeight();
        }
    }

    public void MakeStep()
    {
        this.heights = this.DiamondStep(this.heights);
        this.SquareStep(this.heights);
    }

    private float[,] DiamondStep(float[,] data)
    {
        this.cDeviance *= this.FallOff;

        int oldSize = cSize;
        cSize = cSize * 2 - 1;
        float[,] result = new float[cSize, cSize];

        for (int x = 0, nx = 1; x < oldSize - 1; x++, nx += 2)
            for (int y = 0, ny = 1; y < oldSize - 1; y++, ny += 2)
            {
                float hlt = data[x, y];
                float hrt = data[x + 1, y];
                float hlb = data[x, y + 1];
                float hrb = data[x + 1, y + 1];

                float add = 0f;
                if (y % 2 == 0)
                    if (x % 2 == 0) { add += hrb + hlt; } else { add += hlb + hrt; }
                else
                    if (x % 2 == 0) { add += hrt + hlb; } else { add += hlt + hrb; }

                float mid = (hlt + hrt + hlb + hrb + add) / 6.0f;
                float offset = (this.rand.GetHeight() * this.cDeviance);

                result[nx, ny] = (mid + offset);

                //set existing heights
                result[nx - 1, ny - 1] = hlt;
                result[nx + 1, ny - 1] = hrt;
                result[nx - 1, ny + 1] = hlb;
                result[nx + 1, ny + 1] = hrb;
            }

        return result;
    }

    private void SquareStep(float[,] data)
    {
        for (int y = 0; y < cSize; y++)
            for (int x = y % 2 == 0 ? 1 : 0; x < cSize; x += 2)
            {
                if (data[x, y] != 0)
                    continue;

                float l = (x - 1 < 0) ? float.NaN : data[x - 1, y];
                float r = (x + 1 >= cSize) ? float.NaN : data[x + 1, y];
                float t = (y - 1 < 0) ? float.NaN : data[x, y - 1];
                float b = (y + 1 >= cSize) ? float.NaN : data[x, y + 1];

                if (float.IsNaN(l)) { if (this.Wrap) { data[x, y] = this.GetMissingPoint(cSize - 1, y, data, (r + t + b)); continue; } else l = r; }
                if (float.IsNaN(r)) { if (this.Wrap) { data[x, y] = this.GetMissingPoint(0, y, data, (l + t + b)); continue; } else r = l; }
                if (float.IsNaN(t)) { if (this.Wrap) { data[x, y] = this.GetMissingPoint(x, cSize - 1, data, (l + r + b)); continue; } else t = b; }
                if (float.IsNaN(b)) { if (this.Wrap) { data[x, y] = this.GetMissingPoint(x, 0, data, (l + r + t)); continue; } else b = t; }

                float mid = x % 2 == 0 ? (l + r + t * 2f + b * 2f) / 6.0f : (l * 2f + r * 2f + t + b) / 6.0f;
                float offset = this.rand.GetHeight() * this.cDeviance;

                data[x, y] = (mid + offset);
            }
    }

    private float GetMissingPoint(int x, int y, float[,] data, float height)
    {
        float l = x - 1 < 0 ? float.NaN : data[x - 1, y];
        float r = x + 1 >= cSize ? float.NaN : data[x + 1, y];
        float t = y - 1 < 0 ? float.NaN : data[x, y - 1];
        float b = y + 1 >= cSize ? float.NaN : data[x, y + 1];

        if (float.IsNaN(l)) l = 0;
        if (float.IsNaN(r)) r = 0;
        if (float.IsNaN(b)) b = 0;
        if (float.IsNaN(t)) t = 0;

        float mid = (l + r + t + b + height) / 6.0f;
        float res = mid + (this.rand.GetHeight() * this.cDeviance);
        data[x, y] = res;

        return res;
    }

    public static float Clamp(float value, float min, float max)
    {
        return value > max ? max : value < min ? min : value;
    }
}

public static class MyExtensions
{
    public static float GetHeight(this Random rnd)
    {
        return (float)(rnd.NextDouble() * MidPointHeight.cRange - (MidPointHeight.cRange / 2.0f));
    }
}

public class MeshData
{
    public int Size { get; set; }
    public float[,] Heights { get; set; }
}