These are Command Blocks:


As
you can see these blocks all have arrows pointing up. The arrows can
point in any of the six directions and whichever direction they point
will matter depending on their use. More on that later.

The Purple Block is a Repeating Command Block

The Tan Block is an Impulse Command Block

The Cyan Block is a Chain Command Block


This is what it looks like when you right click on the command block.


As you can see there is a spot for the command and a few instructions just below.

There are also three buttons below. They each have their own set of options. They broken down as follows from Left to Right:

The First Button: (3 options) This correlates to the type of command block that you'll use.

IMPULSE: Operates when activated via redstone or other triggers. [Also this will change the color of the block to Tan]
CHAIN: Operates when activated by another command block. [This changes the color to Cyan]
REPEAT: Operates once per tick. [This changes the color to Purple]

The Second Button: (2 options) Mainly used for Chain Command blocks

UNCONDITIONAL:
This will cause the command block to operate if it receives any kind of signal from a command block pointing toward it.

CONDITIONAL:
This will tell the command block to operate only if it is receiving a positive outcome from another command block pointing toward it.


The Third Button: (2 options)

NEEDS REDSTONE:
This instructs the command block to only operate if it is receiving a redstone signal of any kind.

ALWAYS ACTIVE:
This instructs the command block to operate regardless of redstone input.

Now that we've covered the basics, lets get down to business on how you can use these to your advantage as a map maker.

A lot of mapmakers use void worlds as a starting point for their maps. The upside is it creates a completely blank canvas to build upon. Usually people start building or they'll use a few commands to fill a large-ish spot. This will however make creation of landscape much easier.

To begin You'll need a repeating command block with the following code:

execute @p[tag=XXXX] ~ ~ ~ fill ~ ~-1 ~ ~9 ~-1 ~9 minecraft:stone 0

Simply put, you'll be executing a fill command that makes a platfrom of stone in a 10x10 configuration, just below any player that has a tag of "XXXX". So wherever you walk you'll automatically build a platform.

You can modify the fill command to make the platform as big as you'd like beginning at wherever you're standing as long as you've given yourself the tag that you placed in the space where the XXXX are.

To give yourself a tag type:

/scoreboard players tag "yourname" add XXXX

Where "yourname" is your in game name without quotes, you can also put @p here.

As long as you have the Tag applied to you, you'll place the 10 x 10 platform wherever you walk. If you jump then you'll still continue to make the platform, so be careful.

To remove the tag simply type:

/scoreboard players tag "yourname" remove XXXX

To create a 10 x 10 x 10 cube you can simply type the command:

/fill ~ ~ ~ ~9 ~9 ~9 minecraft:stone 0

to make it a hollow cube you'll just type the following:

/fill ~ ~ ~ ~9 ~9 ~9 minecraft:stone 0 hollow

You can use this to create a building or container of sorts.

If you're making a storage facility or a storage container yard in one of your maps this comes in real handy, unfortunately it takes a bit of time to type up the commands to get the job done.

So a way around this is to combine a few elements to create a placement system that will make it easy to get things done quickly.

First you'll create a repeating [purple] command block that is always active and unconditional with the following command:

execute @p[tag=example_tag] ~ ~ ~ fill ~ ~ ~ ~5 ~12 ~5 minecraft:stained_hardened_clay 1 hollow

This will create an orange container that is 6 x 13 x 6 blocks and hollow.

You'll then want to create a chain [cyan] command block that is always active and unconditional. Make sure it is attached to the repeating command block, with the repeating command block pointing toward this one.

Then give it the following command:

scoreboard players tag @p[tag=example_tag] remove example_tag

This block combination will set a hollow orange container at your location and then remove the tag so that you won't keep creating the container wherever you go.

So now all you have to do is type: scoreboard players tag "yourname" add example_tag

Here is an example of my system that I use for this very purpose:


The lower system places containers that run long on the x axis and have numerical tags that begin at 1x, while the top places containers along the z axis and the tags are alphanumerical and begin at 1z.

So now all I have to do is type the tag command once then open the chat window, hit the up arrow and change the number to place a container of a various color. It makes everything a lot faster when building.

In addition to the above information, I've discovered a way to make it easier to active a command instead of manually adding by typing in a command. To do this nifty little trick, we simply create a command that looks for a player with a certain item in their offhand slot. This is accomplished by creating a Repeating Command Block with this command:

testfor @p {Inventory:[{Slot:-106b,id:minecraft:XXXXX,Count:1b}]}

This will look for any player with a specific item (represented by XXXXX) in their offhand slot. You can also replace @p with your player name. This will prevent anyone from activating the command that isn't supposed to.

For example, If you told the command block to look for sand in the players hand, you could then link it to an "Always Active | Conditional | Chain" command block, that will create a platform. You will then make a platform wherever you walk as long as you're holding a sand block in your offhand.

This makes activating and deactivating commands much easier. You can use this for anything, such as a message broadcast with titles to players in a radius of someone holding a clock announcing the time. The possibilities are far reaching.

Unfortunately I haven't figured out a way to make a single command block that will build a customized building. I'm sure they're out there, but I don't have any here.

What I can tell you is that you can use a similar mechanic to the previous section that will allow you to copy and paste structures to anywhere in your map.

Simply use the same tag system but instead of using the fill command in the first command block, you'll use:

execute @p[tag=example_tag] ~ ~ ~ clone x1 y1 z1 x2 y2 z2 ~ ~ ~

This will clone a structure at x1, y1, z1, x2, y2, z2 to the spot where you're standing.

It's possible that you'll make mistakes from time to time. It is generally wise to create an "Undo" command. All you'd have to do is add a piece to your system that sets the same blocks as anything else you've created to Air.

There is also, what could be considered one of the easiest ways to grief.

In a repeating always active command block place this command:

execute @p[tag=example_tag] ~ ~ ~ fill ~-10 ~-10 ~-10 ~10 ~10 ~10 minecraft:air

This will erase all the blocks around you in a 21 x 21 x 21 cube with you in the center.

USE THIS WISELY AND WITH CAUTION - it is handy to have, but can be exploited for griefing on a massive scale.