NBTTagCompound lensCmp = new NBTTagCompound();
if(stack != null)
stack.writeToNBT(lensCmp);
par1nbtTagCompound.setTag(TAG_LENS_STACK, lensCmp);
ChunkCoordinates coords = getBurstSourceChunkCoordinates();
par1nbtTagCompound.setInteger(TAG_SPREADER_X, coords.posX);
par1nbtTagCompound.setInteger(TAG_SPREADER_Y, coords.posY);
par1nbtTagCompound.setInteger(TAG_SPREADER_Z, coords.posZ);
par1nbtTagCompound.setDouble(TAG_LAST_MOTION_X, motionX);