I am trying to make a Hammer in 1.12.2.  I know, the regular, typical Hammer, once again in another mod. 
Overall I got the 3x3 Working, it breaks. Here is the code:

	public EnumActionResult onItemUse(EntityPlayer player, World worldIn, BlockPos pos, EnumHand hand,
			EnumFacing facing, float hitX, float hitY, float hitZ) {

		if (player.isSneaking()) {
			
			AxisAlignedBB grid = (new AxisAlignedBB(pos.getX(), pos.getY(), pos.getZ(), (pos.getX() + 3),
					(pos.getY() + 3), (pos.getZ() + 3)));
			for (int x = (int) grid.minX; x < (int) grid.maxX; x++) {
				for (int y = (int) grid.minY; y < (int) grid.maxY; y++) {
					for (int z = (int) grid.minZ; z < (int) grid.maxZ; z++) {
						BlockPos newpos = new BlockPos(x, y, z);
						if (worldIn.getBlockState(newpos).getBlock() != Blocks.AIR) {
							worldIn.destroyBlock(newpos, true);
						}
					}
				}
			}

			return EnumActionResult.PASS;

		} else if (!player.isSneaking()) {
			worldIn.destroyBlock(pos, true);

			return EnumActionResult.PASS;
		}
		return EnumActionResult.FAIL;
	}

However I have been messing around with it and I did not get it to work in the sense that I wanted, which is starting from the middle and breaking top,down, left and right.
I did try the top and down method. pos.up() pos.down() etc but that did not work when I did the whole facing checks. So it would be different for when I looked east, or when I looked north. I did fix that, but when I looked up or down, it did not.
I guess it was because it checked player Horizontal Plane for Direction..

 

Anyway Results Below:

 

 

Its starting from bottom left to top right.
I have been trying to get it into the middle block and it does it around

Edited March 8, 20205 yr by MinecraftDW2020
Solved The Problem

If you want to break only 9 blocks (and not 27) you need to know either:

a) which direction the player is facing 

b) which side of the block the player was aiming at

Just now, Draco18s said:

If you want to break only 9 blocks (and not 27) you need to know either:

 a) which direction the player is facing 

b) which side of the block the player was aiming at

No, I got the breaking part to work. Just not the actual placement.
 

 

23 minutes ago, MinecraftDW2020 said:

Its starting from bottom left to top right.
I have been trying to get it into the middle block and it does it around

 

You mean, starting in the center?

Your problem is here:

 

AxisAlignedBB grid = (new AxisAlignedBB(pos.getX(), pos.getY(), pos.getZ(), (pos.getX() + 3),
					(pos.getY() + 3), (pos.getZ() + 3)));

 

You need to subtract 1 from the first three values and only add 1 to the last three. so the range is -1, 0, 1.

32 minutes ago, Draco18s said:

You mean, starting in the center?

Your problem is here:

 

AxisAlignedBB grid = (new AxisAlignedBB(pos.getX(), pos.getY(), pos.getZ(), (pos.getX() + 3),
					(pos.getY() + 3), (pos.getZ() + 3)));

 

You need to subtract 1 from the first three values and only add 1 to the last three. so the range is -1, 0, 1.

Well Thanks, That worked, it got to the middle but now it breaks two layer at a time, and I think it is because of the for loop, for the past 30 minutes I have been trying to get it to not do that, I tried changing the greater than signs around, messing around with min and max even more, and just doing other experimenting to it.

Well, you're breaking a 3x3x3 cube because of your offsets.

As I said, if I want a 3x3x1, you need to know either the facing of the player or the side that was hit so you can determine which of the three directions should be only 1 unit thick.

1 hour ago, Draco18s said:

Well, you're breaking a 3x3x3 cube because of your offsets.

As I said, if I want a 3x3x1, you need to know either the facing of the player or the side that was hit so you can determine which of the three directions should be only 1 unit thick.

Yeah nevermind, I did that in my old method, got both confused, I decided to experiment with more on my old method instead and it felt much better. Not short but still remembered to do the facings.
Well now it is solved