Stack overflow with C# and Mono, recursive function

Question

I'm using Unity3D based on the Mono framework and C#. The function below throw Stack Overflows. I cannot figure out where these come from; normally nowadays this tends to happen only with infinite loops, which mine isn't. It works fine with 8x8x16 voxels, but crashes at 16x16x32 voxels. I put a lock in because I figure it might happen that the function is fired for a second time before the first finished.

int FloatingVoxelsFlood(int x, int y, int z, ref bool[] voxelsAttached) {
    if (GetPixel(x, y, z).a > 0.5f) return 0;

    int id = GetPixelId(x, y, z);
    if (voxelsAttached[id]) return 0;

    voxelsAttached[id] = true;

    int count = 1;

    int minx = x-1;
    int maxx = x+1;
    if (minx >= 0) 
        count += FloatingVoxelsFlood(minx, y, z, ref voxelsAttached);
    if (maxx < volumeWidth) 
        count += FloatingVoxelsFlood(maxx, y, z, ref voxelsAttached);

    int miny = y-1;
    int maxy = y+1;
    if (miny >= 0) 
        count += FloatingVoxelsFlood(x, miny, z, ref voxelsAttached);
    if (maxy < volumeHeight) 
        count += FloatingVoxelsFlood(x, maxy, z, ref voxelsAttached);

    int minz = z-1;
    int maxz = z+1;
    if (minz >= 0) 
        count += FloatingVoxelsFlood(x, y, minz, ref voxelsAttached);
    if (maxz < volumeDepth) 
        count += FloatingVoxelsFlood(x, y, maxz, ref voxelsAttached);

    return count;
}

voxelsAttached is set to all false at start. GetPixel().a returns if a voxel needs to be used.

How can I solve this stack overflow?

Answer 1

The one below does not overflow the stack.

int FloatingVoxelsFlood(int x, int y, int z, ref bool[] voxelsAttached) {
    if (GetPixel(x, y, z).a > 0.5f) return 0;

    Queue<Pixel> queue = new Queue<Pixel>();
    queue.Enqueue(new Pixel(x, y, z));

    int count = 0;
    while(queue.Count > 0) {
        Pixel p = queue.Dequeue();

        int id = GetPixelId(p.x, p.y, p.z);
        if (!voxelsAttached[id] && GetPixel(p.x, p.y, p.z).a < 0.5f) {
            count++;
            voxelsAttached[id] = true;

            int minx = p.x-1;
            int maxx = p.x+1;
            if (minx >= 0) 
                queue.Enqueue(new Pixel(minx, p.y, p.z));
            if (maxx < volumeWidth) 
                queue.Enqueue(new Pixel(maxx, p.y, p.z));

            int miny = p.y-1;
            int maxy = p.y+1;
            if (miny >= 0) 
                queue.Enqueue(new Pixel(p.x, miny, p.z));
            if (maxy < volumeHeight) 
                queue.Enqueue(new Pixel(p.x, maxy, p.z));

            int minz = p.z-1;
            int maxz = p.z+1;
            if (minz >= 0) 
                queue.Enqueue(new Pixel(p.x, p.y, minz));
            if (maxz < volumeDepth) 
                queue.Enqueue(new Pixel(p.x, p.y, maxz));
        }
    }

    return count;
}