private MCAFile getMCA(int x, int y, int z) {
   int MCAX = x >> 9;
   int MCAZ = z >> 9;
   if (MCAX == lastX && MCAZ == lastZ) {
     return lastMCA;
   }
   lastX = MCAX;
   lastZ = MCAZ;
   long pair = MathMan.pairInt(lastX, lastZ);
   lastMCA = regions.get(pair);
   if (lastMCA == null) {
     //            lastMCA = new MCAFile(folder, lastX, lastZ);
     // TODO
     regions.put(pair, lastMCA);
   }
   return lastMCA;
 }
 public int getOpacityBrightnessPair(int x, int y, int z) {
   return MathMan.pair16(Math.min(15, getOpacity(x, y, z)), getBrightness(x, y, z));
 }