Question

我正在编写自己的中点位移算法用于学习目的，我决定以自己的方式实现它，看看我是否能够理解算法，2）看看我是否可以根据自己的喜好修改它。 / p>

这是生成分形的代码：

 public void Generate(Double rg, int size)
    {
        Random rand = new Random();
        int min = -127;
        int max = 128;

        // Starting points of the rectangle
        MDP_Point s1 = new MDP_Point(0, 0, rand.Next(min, max));
        MDP_Point s2 = new MDP_Point(size, 0, rand.Next(min, max));
        MDP_Point s3 = new MDP_Point(size, size, rand.Next(min, max));
        MDP_Point s4 = new MDP_Point(0, size, rand.Next(min, max));

        // Lists containing the rectangles
        List<MDP_Rect> newRect = new List<MDP_Rect>();  // Newly created rectangles
        List<MDP_Rect> oldRect = new List<MDP_Rect>();  // Rectangles being divided


        // Starting rectangle is added to the list
        oldRect.Add(new MDP_Rect(s1, s2, s3, s4));

        // Distance between 2 points in a rectangle
        int h = size;

        while (h > 1)
        {
            foreach (MDP_Rect r in oldRect)
            {
                // Middle points of rectangle segments
                MDP_Point m1 = new MDP_Point();
                MDP_Point m2 = new MDP_Point();
                MDP_Point m3 = new MDP_Point();
                MDP_Point m4 = new MDP_Point();
                // Middle point of rectangle
                MDP_Point mm = new MDP_Point();

                m1.x = (r.C1.x + r.C2.x) / 2;
                m1.y = (r.C1.y + r.C2.y) / 2;
                m1.z = ((r.C1.z + r.C2.z) / 2) +(rand.Next(min, max) * rg);

                m2.x = (r.C2.x + r.C3.x) / 2;
                m2.y = (r.C2.y + r.C3.y) / 2;
                m2.z = ((r.C2.z + r.C3.z) / 2) +(rand.Next(min, max) * rg);

                m3.x = (r.C3.x + r.C4.x) / 2;
                m3.y = (r.C3.y + r.C4.y) / 2;
                m3.z = ((r.C3.z + r.C4.z) / 2) +(rand.Next(min, max) * rg);

                m4.x = (r.C1.x + r.C4.x) / 2;
                m4.y = (r.C1.y + r.C4.y) / 2;
                m4.z = ((r.C1.z + r.C4.z) / 2) + (rand.Next(min, max) * rg);

                mm.x = (r.C1.x + r.C2.x + r.C3.x + r.C4.x) / 4;
                mm.y = (r.C1.y + r.C2.y + r.C3.y + r.C4.y) / 4;
                mm.z = ((r.C1.z + r.C2.z + r.C3.z + r.C4.z) / 4) + (rand.Next(min, max) * rg);

                newRect.Add(new MDP_Rect(r.C1, m1, mm, m4));
                newRect.Add(new MDP_Rect(m1, r.C2, m2, mm));
                newRect.Add(new MDP_Rect(mm, m2, r.C3, m3));
                newRect.Add(new MDP_Rect(m4, mm, m3, r.C4));
            }


            oldRect.Clear();
            oldRect = new List<MDP_Rect>(newRect);
            newRect.Clear();
            h /= 2;
        }

        List<MDP_Rect> sorted = new List<MDP_Rect>();
        sorted = oldRect.OrderBy(y => y.C1.y).ThenBy(x => x.C1.x).ToList();

        List<MDP_Point> mapArray = new List<MDP_Point>();
        mapArray.AddRange(CreateArray(sorted));

        CreateImage(size, mapArray, rg);
    }

MDP_Point仅包含x，y和z值 MDP_Rectangle包含4个点，创建一个矩形

CreateArray（）方法仅以正确的顺序获取有序矩形列表和输出以及点列表以创建图像。

CreateArray（）：

        private List<MDP_Point> CreateArray(List<MDP_Rect> lRect)
    {
        List<MDP_Point> p = new List<MDP_Point>();

        int size = (int)Math.Sqrt(lRect.Count);

        int i = 0;
        foreach (MDP_Rect r in lRect)
        {
            p.Add(new MDP_Point((int)r.C1.x, (int)r.C1.y, (int)r.C1.z));

            if (i > 0 && i % size == size - 1)
            {
                p.Add(new MDP_Point((int)r.C2.x, (int)r.C2.y, (int)r.C2.z));
            }

            i++;
        }

        for (int a = 0; a < size; a++)
        {
            p.Add(new MDP_Point((int)lRect[(size * size - size) + a].C4.x,
                (int)lRect[(size * size - size) + a].C4.y,
                (int)lRect[(size * size - size) + a].C4.z));

            if (a > 0 && a % size == size - 1)
            {
                p.Add(new MDP_Point((int)lRect[(size * size - size) + a].C3.x,
                    (int)lRect[(size * size - size) + a].C3.y,
                    (int)lRect[(size * size - size) + a].C3.z));
            }
        }

        return p;
    }

这是创建图像的方法：

        private void CreateImage(int size, List<MDP_Point> arr, double roughness)
    {
        Bitmap map = new Bitmap(size, size);

        int ver = 0;
        for (int i = 0; i < map.Height; i++)
        {
            for (int n = 0; n < map.Width; n++ )
            {
                int h = (int)arr[ver].z + 127;
                if (h < 0)
                {
                    h = 0;
                }
                else if (h > 255)
                {
                    h = 255 ;
                }
                Color c = Color.FromArgb(h, h, h);

                //map.SetPixel(n, i, c);
                map.SetPixel(i, n, c);
                ver++;
            }
        }

        Bitmap m = new Bitmap(map);
        bool saved = true;
        int num = 0;

        while (saved)
        {
            if (File.Exists("map_S" + size + "_R" + roughness + "_" + num + ".png"))
            {
                num++;
            }
            else
            {
                m.Save("map_S" + size + "_R" + roughness + "_" + num + ".png", System.Drawing.Imaging.ImageFormat.Png);
                saved = false;
            }
        }

        map.Dispose();
        m.Dispose();
    }

任何低于0的值都设置为0，高于255的任何值设置为255这一事实可能是个大问题....不知道该怎么做。

这是代码生成的图像：大小：1024 粗糙度：0.5

enter image description here

最明显的问题是对角线“脊线”和平铺外观。

此时，我不知道如何解决这个问题，让它看起来更自然。有什么想法吗？

Answer 1

在这里，我认为问题的一部分是您使用255和0攻击h变量。我尝试使用以下代码：

int h = (int) arr[ver].z;
if (h < 0)
{
    h = Math.Abs(h);
}
while(h > 255)
{
    h -= 255;
}

在我的电脑上，结果是： Take 1

当我用的时候：

int h = (int) arr[ver].z + 127;

Take 2

注意我只需要创建一个测试MDP_Point类和MDP_Rect来测试这个...

Answer 2

为避免这些伪影，您应该使用Peitgen等人提出的两阶段方法。在“分形图像科学”中。他们还建议在每个细分步骤后向所有顶点添加额外的随机位移。我在这里找到了一个扫描的摘录（第45页）：

http://cs455.cs.byu.edu/lectureslides/FractalsPart2.pdf

中点位移算法 - 奇怪的结果

2 个答案: