bool mengerSponge(double x, double y, double z) {

if(x<0 || x>1 || y<0 || y>1 || z<0 || z>1 )     { return 0; } // point is not part of menger sponge

int iterations=8;

double depth=3;

for(int iter=0; iter<iterations; iter++) {
int holex=1;
while(holex<depth) {
int holey=1;
while(holey<depth) {
if(
((x > holex/depth && x< (holex+1) /depth) && (y > holey/depth && y< (holey+1) /depth)) ||
((y > holex/depth && y< (holex+1) /depth) && (z > holey/depth && z< (holey+1) /depth)) ||
((x > holex/depth && x< (holex+1) /depth) && (z > holey/depth && z< (holey+1) /depth))
) { return 0; } // point is not part of menger sponge
holey+=3;
}
holex+=3;
}
depth*=3;
}

return 1; // point is part of menger sponge
}