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I created this method to trim 3D arrays to use in Octrees. For some weird reason that I cant figure out after returning the trimmed array its just full of zeros. When it should be filled with ones.

Here is the code to better explain:

    int[][][] arr = new int[128][128][128];//Create a 3D array of size 128*128*128
    for (int y = 0; y < arr[0][0].length; y++)
        for (int x = 0; x < arr.length; x++)
            for (int z = 0; z < arr[0].length; z++)
                arr[x][z][y] = 1; //Fill the array with ones
    printMatrix(arr); //PRINT "ERROR" IF A ZERO IS FOUND (Note at this call no zeros are found)
    int[][][] arrTrim = trimMatrix(arr,0,0,0,128); //Trim the array using the method (Note in octrees I would use this method multiple times)
    printMatrix(arrTrim); //Check if there are zeros in the new trimmed array (Note: at this call the array is full of zeros)

The print matrix method (its used to only print the zeros to check if there are any) (there shouldnt be any):

    private static void printMatrix(int[][][] arr) {
    System.out.println("Arr ------------------ {");
    for (int y = 0; y < arr[0][0].length; y++)
        for (int x = 0; x < arr.length; x++)
            for (int z = 0; z < arr[0].length; z++)
                if (arr[x][z][y] == 0)
                    System.out.print(" ERROR | "+arr[x][z][y]+" at "+x+","+z+","+y+" | ");
    System.out.println(" } ------------------");
}

The trim method (x,z,y is there to say where to start trimming so you could trim the 3D array into 8 parts for the Octree) (Note: suicide never happens meaning the voxels array never has zeros):

private static int[][][] trimMatrix(int[][][] voxel, float x, float z, float y, float size) {
    int[][][] temp = new int[voxel.length/2][voxel[0].length/2][voxel[0][0].length/2]; //Create a new temp array of half size (64)
    float varx = x * ( size/2); //Determine where to start (x can be 0 or 1)
    float vary = y * (size/2); //Determine where to start (y can be 0 or 1)
    float varz = z * (size/2); //Determine where to start (z can be 0 or 1)

    int incx = 0 , incy = 0 , incz = 0; //Increments for the temp array
    for (int yy = (int) vary; incy < temp[0][0].length; yy++, incy++) {
        for (int xx = (int) varx; incx < temp.length; xx++, incx++) {
            for (int zz = (int) varz; incz < temp[0].length; zz++, incz++) {
                temp[incx][incz][incy] = voxel[xx][zz][yy];//Set in temp the value of voxel which should be 1 (it is one)
                if (voxel[xx][zz][yy] == 0) { //if its zero kill the program (This never happens)
                    System.out.println("Suicide at "+xx+":"+incx);
                    System.exit(-1);
                }
            }
        }
    }

    return temp; //Return the new trimmed array full of ones (which turns out is full of zeros)
}

Now I am not a Java newbie for any stretch of the imagination but I can not figure out why this is acting up.

Amit Assaraf
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  • For a start, the naming of printMatrix isn't very good. It does not print the Matrix. Secondly, what does temp contain just before the return temp; in trimMatrix? (System.out.println(Arrays.toString(trim);) – Burkhard Jun 11 '13 at 11:17
  • The naming is just for testing the method. – Amit Assaraf Jun 11 '13 at 11:49

1 Answers1

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Your test for the inner loop is incz < temp[0].length. But you never reset incz to zero. You set it to zero once at the beginning, then never again.

So you're actually going through one vector in one dimension, and all the next vectors are being skipped.

Frankly, a simple session with a debugger should've discovered this.

Joeri Hendrickx
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