Hi, I'm having problems again with another algorithm. This time it is the Diamond-Square algorithm(htpp://www.gameprogrammer.com/fractal.html if you are interested)
It is producing the desired effect, sort of. It is suppose to randomize all y values to non-zero values, however it only does about a quarter of them. Any help would be much appriciated.
Code:
// Brad Galloway
// Diamond-Square Implementation
// First compile: April 16th, 2005
#include<fstream>
#include<iostream>
#include<ctime>
#include<cstdlib>
#include<cmath>
using namespace std;
const int ARRAY_SIZE = 33;
struct point{
float x;
float y;
float z;
};
point array[ARRAY_SIZE][ARRAY_SIZE];
float random_number(){
//Generates a random floating point number
srand(time(NULL));
int random = (rand() % 200) - 100;
float return_value = (float)random / 100.0f;
return return_value;
}
void create_array(){
for(int i = 0; i < ARRAY_SIZE; i++){
for(int j = 0; j < ARRAY_SIZE; j++){
array[i][j].x = (float)j - (float)(ARRAY_SIZE/2);
array[i][j].y = 0.0f;
array[i][j].z = (float)i - (float)(ARRAY_SIZE/2);
}
}
}
void diamond_step(int s, int n) //s = size of squares in this step, n = number of squares
{
int count = 0; //keeps track of the column we are modifying.
int xstart = 0; //Keeps track of the starting location for this square x
int zstart = 0; //Keeps track of the starting location for this square z
float average; //Holds the average of the for corners
for(int i = 0; i < n; i++){ //Loops equal to the number of squares to be done in this time
// average = (corner1 + corner2 + corner3 + corner4)/4
average = (array[xstart][zstart].y + array[xstart + s][zstart].y +
array[xstart][zstart + s].y + array[xstart + s][zstart + s].y)/4.0f;
if(array[s/2 + 1 + xstart][s/2 + 1 + zstart].y == 0)
array[s/2 + 1 + xstart][s/2 + 1 + zstart].y += average + random_number();
count++; //Add one to count
if(count^2 == n){ //If count squared equals n
count = 0; //then set count to 0
xstart = 0; //set xstart back to 0
zstart += s; //increment zstart
}
else{
xstart += s; //if not, increment xstart and do the next square
};
}
}
void square_step(int half_size, int n){// Note xspot and zspot correspond to the points in the array that contain the data, not the data itself.
int count_dia = 0;
int test_number = (int)sqrt((float)n);
if(test_number == 0)
test_number = 1;
int xspot = (((ARRAY_SIZE/test_number)/2)+1);
int zspot = (((ARRAY_SIZE/test_number)/2)+1);
int xbegin = xspot;
float average_dia_left; //Keeps track of the average heights for the four diamonds
float average_dia_top; //around the axis.
float average_dia_right;
float average_dia_bottom;
for(int i = 0; i < n; i++){
if(xspot >= (half_size * 2)){ //Left
average_dia_left = array[xspot][zspot].y + array[xspot - half_size][zspot + half_size].y
+ array[xspot - (half_size * 2)][zspot].y + array[xspot - half_size][zspot - half_size].y;
}
else{ //If the axis is on next to the outside of the array
average_dia_left = array[xspot][zspot].y + array[xspot - half_size][zspot + half_size].y
+ array[xspot - half_size][zspot - half_size].y;
}
if(zspot >= (half_size * 2)){ //Top
average_dia_top = array[xspot][zspot].y + array[xspot - half_size][zspot - half_size].y
+ array[xspot][zspot - (half_size * 2)].y + array[xspot + half_size][zspot + half_size].y;
}
else{ //If the axis is on next to the outside of the array
average_dia_top = array[xspot][zspot].y + array[xspot - half_size][zspot - half_size].y
+ array[xspot + half_size][zspot + half_size].y;
}
if(xspot + (half_size * 2) <= ARRAY_SIZE){ //Right
average_dia_right = array[xspot][zspot].y + array[xspot + half_size][zspot - half_size].y
+ array[xspot + (half_size * 2)][zspot].y + array[xspot + half_size][zspot + half_size].y;
}
else{ //If the axis is on next to the outside of the array
average_dia_right = array[xspot][zspot].y + array[xspot + half_size][zspot - half_size].y
+ array[xspot + half_size][zspot + half_size].y;
}
if(zspot + (half_size * 2) <= ARRAY_SIZE){ //Bottom
average_dia_bottom = array[xspot][zspot].y + array[xspot + half_size][zspot + half_size].y
+ array[xspot][zspot + (half_size * 2)].y + array[xspot - half_size][zspot + half_size].y;
}
else{ //If the axis is on next to the outside of the array
average_dia_bottom = array[xspot][zspot].y + array[xspot + half_size][zspot + half_size].y
+ array[xspot - half_size][zspot + half_size].y;
}
if(array[xspot - half_size][zspot].y == 0){ //Left
array[xspot - half_size][zspot].y += average_dia_left + random_number();
}
if(array[xspot][zspot - half_size].y == 0){ //Top
array[xspot][zspot - half_size].y += average_dia_top + random_number();
}
if(array[xspot + half_size][zspot].y == 0){ //Right
array[xspot + half_size][zspot].y += average_dia_right + random_number();
}
if(array[xspot][zspot + half_size].y == 0){ //Bottom
array[xspot][zspot + half_size].y += average_dia_bottom + random_number();
}
count_dia++; //Add one to count
if(count_dia^2 == n){ //If count squared equals n
count_dia = 0; //then set count to 0
xspot = xbegin; //set xspot back to Initial step
zspot += half_size * 2; //increment zstart
}
else{
xspot += half_size * 2; //if not, increment xstart and do the next square
};
}
}
void print_array(){
char filename[11] = "output.txt";
ofstream outFile( filename );
for(int j = 0; j < ARRAY_SIZE; j++){
for(int i = 0; i < ARRAY_SIZE; i++){
outFile << "(" << array[i][j].x << ", " << array[i][j].y << ", " << array[i][j].z << ") ";
}
outFile << endl;
}
cout << "File created 'output.txt'";
}
int main(){
int num_cells = (ARRAY_SIZE - 1)^2;
bool done = false;
int q = 1; //quotient for figuring the size of the squares and number of squares
create_array();
while(!done){
diamond_step(num_cells/q, q^2);
square_step((num_cells/q)/2, q^2);
q *= 2;
if(q > num_cells)
done = true;
}
print_array();
return 1;
}
All these years I've been using that as the exponent operator in my programs. The only question is how did it get stucky in my head that way? Probably Qbasic.
Linear Mode
