M. *_*sup 26
这是一种用于生成值的有趣算法.这是我根据维基百科文章的参考资料在此页面上给出的解释创建的实现.它将创建"球形值"(包裹在所有边缘).评论中有注释如何更改它以在边缘上生成新值而不是包装(尽管在这些情况下边缘的平均值不正确).
//size of grid to generate, note this must be a
//value 2^n+1
final int DATA_SIZE = 9;
//an initial seed value for the corners of the data
final double SEED = 1000.0;
double[][] data = new double[DATA_SIZE][DATA_SIZE];
//seed the data
data[0][0] = data[0][DATA_SIZE-1] = data[DATA_SIZE-1][0] =
data[DATA_SIZE-1][DATA_SIZE-1] = SEED;
double h = 500.0;//the range (-h -> +h) for the average offset
Random r = new Random();//for the new value in range of h
//side length is distance of a single square side
//or distance of diagonal in diamond
for(int sideLength = DATA_SIZE-1;
//side length must be >= 2 so we always have
//a new value (if its 1 we overwrite existing values
//on the last iteration)
sideLength >= 2;
//each iteration we are looking at smaller squares
//diamonds, and we decrease the variation of the offset
sideLength /=2, h/= 2.0){
//half the length of the side of a square
//or distance from diamond center to one corner
//(just to make calcs below a little clearer)
int halfSide = sideLength/2;
//generate the new square values
for(int x=0;x<DATA_SIZE-1;x+=sideLength){
for(int y=0;y<DATA_SIZE-1;y+=sideLength){
//x, y is upper left corner of square
//calculate average of existing corners
double avg = data[x][y] + //top left
data[x+sideLength][y] +//top right
data[x][y+sideLength] + //lower left
data[x+sideLength][y+sideLength];//lower right
avg /= 4.0;
//center is average plus random offset
data[x+halfSide][y+halfSide] =
//We calculate random value in range of 2h
//and then subtract h so the end value is
//in the range (-h, +h)
avg + (r.nextDouble()*2*h) - h;
}
}
//generate the diamond values
//since the diamonds are staggered we only move x
//by half side
//NOTE: if the data shouldn't wrap then x < DATA_SIZE
//to generate the far edge values
for(int x=0;x<DATA_SIZE-1;x+=halfSide){
//and y is x offset by half a side, but moved by
//the full side length
//NOTE: if the data shouldn't wrap then y < DATA_SIZE
//to generate the far edge values
for(int y=(x+halfSide)%sideLength;y<DATA_SIZE-1;y+=sideLength){
//x, y is center of diamond
//note we must use mod and add DATA_SIZE for subtraction
//so that we can wrap around the array to find the corners
double avg =
data[(x-halfSide+DATA_SIZE)%DATA_SIZE][y] + //left of center
data[(x+halfSide)%DATA_SIZE][y] + //right of center
data[x][(y+halfSide)%DATA_SIZE] + //below center
data[x][(y-halfSide+DATA_SIZE)%DATA_SIZE]; //above center
avg /= 4.0;
//new value = average plus random offset
//We calculate random value in range of 2h
//and then subtract h so the end value is
//in the range (-h, +h)
avg = avg + (r.nextDouble()*2*h) - h;
//update value for center of diamond
data[x][y] = avg;
//wrap values on the edges, remove
//this and adjust loop condition above
//for non-wrapping values.
if(x == 0) data[DATA_SIZE-1][y] = avg;
if(y == 0) data[x][DATA_SIZE-1] = avg;
}
}
}
//print out the data
for(double[] row : data){
for(double d : row){
System.out.printf("%8.3f ", d);
}
System.out.println();
}
Chr*_*ley 14
M. Jessup的答案似乎有些小问题.他在哪里:
double avg = data[(x-halfSide+DATA_SIZE)%DATA_SIZE][y] + //left of center data[(x+halfSide)%DATA_SIZE][y] + //right of center data[x][(y+halfSide)%DATA_SIZE] + //below center data[x][(y-halfSide+DATA_SIZE)%DATA_SIZE]; //above center
它应该改为:
double avg = data[(x-halfSide+DATA_SIZE-1)%(DATA_SIZE-1)][y] + //left of center data[(x+halfSide)%(DATA_SIZE-1)][y] + //right of center data[x][(y+halfSide)%(DATA_SIZE-1)] + //below center data[x][(y-halfSide+DATA_SIZE-1)%(DATA_SIZE-1)]; //above center
否则它从错误的位置读取(可能是未初始化的).
对于任何人来说,这里是由M. Jessup提供的算法,包含在一个接收种子的类中(允许重现结果),n的值用于指定维度(维度为2 ^ n + 1),并暴露结果作为规范化的浮点数组.它还修复了应用算法的第二部分.
import java.util.Random;
public class DiamondSquare {
public float[][] data;
public int width;
public int height;
public DiamondSquare(long mseed, int n) {
//size of grid to generate, note this must be a
//value 2^n+1
int DATA_SIZE = (1 << n) + 1;
width = DATA_SIZE;
height = DATA_SIZE;
//an initial seed value for the corners of the data
final float SEED = 1000.0f;
data = new float[DATA_SIZE][DATA_SIZE];
//seed the data
data[0][0] = data[0][DATA_SIZE-1] = data[DATA_SIZE-1][0] =
data[DATA_SIZE-1][DATA_SIZE-1] = SEED;
float valmin = Float.MAX_VALUE;
float valmax = Float.MIN_VALUE;
float h = 500.0f;//the range (-h -> +h) for the average offset
Random r = new Random(mseed);//for the new value in range of h
//side length is distance of a single square side
//or distance of diagonal in diamond
for(int sideLength = DATA_SIZE-1;
//side length must be >= 2 so we always have
//a new value (if its 1 we overwrite existing values
//on the last iteration)
sideLength >= 2;
//each iteration we are looking at smaller squares
//diamonds, and we decrease the variation of the offset
sideLength /=2, h/= 2.0){
//half the length of the side of a square
//or distance from diamond center to one corner
//(just to make calcs below a little clearer)
int halfSide = sideLength/2;
//generate the new square values
for(int x=0;x<DATA_SIZE-1;x+=sideLength){
for(int y=0;y<DATA_SIZE-1;y+=sideLength){
//x, y is upper left corner of square
//calculate average of existing corners
float avg = data[x][y] + //top left
data[x+sideLength][y] +//top right
data[x][y+sideLength] + //lower left
data[x+sideLength][y+sideLength];//lower right
avg /= 4.0;
//center is average plus random offset
data[x+halfSide][y+halfSide] =
//We calculate random value in range of 2h
//and then subtract h so the end value is
//in the range (-h, +h)
avg + (r.nextFloat()*2*h) - h;
valmax = Math.max(valmax, data[x+halfSide][y+halfSide]);
valmin = Math.min(valmin, data[x+halfSide][y+halfSide]);
}
}
//generate the diamond values
//since the diamonds are staggered we only move x
//by half side
//NOTE: if the data shouldn't wrap then x < DATA_SIZE
//to generate the far edge values
for(int x=0;x<DATA_SIZE-1;x+=halfSide){
//and y is x offset by half a side, but moved by
//the full side length
//NOTE: if the data shouldn't wrap then y < DATA_SIZE
//to generate the far edge values
for(int y=(x+halfSide)%sideLength;y<DATA_SIZE-1;y+=sideLength){
//x, y is center of diamond
//note we must use mod and add DATA_SIZE for subtraction
//so that we can wrap around the array to find the corners
float avg =
data[(x-halfSide+DATA_SIZE-1)%(DATA_SIZE-1)][y] + //left of center
data[(x+halfSide)%(DATA_SIZE-1)][y] + //right of center
data[x][(y+halfSide)%(DATA_SIZE-1)] + //below center
data[x][(y-halfSide+DATA_SIZE-1)%(DATA_SIZE-1)]; //above center
avg /= 4.0;
//new value = average plus random offset
//We calculate random value in range of 2h
//and then subtract h so the end value is
//in the range (-h, +h)
avg = avg + (r.nextFloat()*2*h) - h;
//update value for center of diamond
data[x][y] = avg;
valmax = Math.max(valmax, avg);
valmin = Math.min(valmin, avg);
//wrap values on the edges, remove
//this and adjust loop condition above
//for non-wrapping values.
if(x == 0) data[DATA_SIZE-1][y] = avg;
if(y == 0) data[x][DATA_SIZE-1] = avg;
}
}
}
for(int i=0; i<width; i++) {
for(int j=0; j<height; j++) {
data[i][j] = (data[i][j] - valmin) / (valmax - valmin);
}
}
}
}