BlockCompanion

BlockCompanion

BlockCompanion shows a schematic in your world as see-through "ghost" blocks. You build over them, block by block. It does the same job as Litematica, but with less on screen and simpler controls.

It also works with BlockDesigner, a Windows app for designing Minecraft builds. You can open BlockDesigner's files in the game, save builds back to it, and link the game and the app live.

BlockCompanion is still in early development. Please report bugs and ideas on the issue tracker.

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What you need

Loader	Minecraft	Java	Also needs
Fabric	1.21.1	21	Fabric API
Fabric	26.2	25	Fabric API
Fabric	26.3	25	Fabric API
NeoForge	1.21.1	21	nothing else
NeoForge	26.2	25	nothing else
NeoForge	26.3	25	nothing else

Mod Menu is optional on Fabric. It lets you open the settings from the mod list.

BlockCompanion is a client mod and works on normal servers. If the server has it too (or the BlockCompanion plugin on Paper or Spigot), you also get shared schematics, AutoBuild and blocks fetched from your chests.

Getting started

1. Install the jar for your loader and Minecraft version (and Fabric API on Fabric).
2. Start the game once. This makes the folder <game folder>/blockcompanion/schematics.
3. Put your schematics in that folder. The schematic screen has an Open folder button.
4. Press B, pick a schematic and click Load. It appears in front of you.
5. Hold a stick and look at the schematic to move, turn and mirror it. Then start building.

New to it? Click BlockCompanion tutorial on the title screen. It opens a practice world that teaches you one step at a time. A short guide also opens the first time you join a world, and you can open it again from the Guide button.

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Features

Schematics

• Opens BlockDesigner projects (.bdproj) and Sponge schematics (.schem). Litematica (.litematic) and vanilla structure (.nbt) files work too.
• A BlockDesigner project loads as one schematic, with all its visible layers.
• Load several schematics at once. Each one remembers where you put it, per world and server.
• Lock a schematic so you can't move it by mistake. A locked one has a blue outline.
• Save from the world: mark two corners with the stick, press O and give it a name. It saves as a .schem file, with chest contents, signs and mobs, ready for BlockDesigner.

A clean view

• Only what is wrong or missing is shown:
  • a ghost where a block is missing
  • red over a wrong block
  • orange where something is in the way (grass, flowers, water and snow don't count)
• Ghosts look like the real blocks and follow your resource packs.
• When you place the right block, its ghost disappears straight away.
• The schematic's outline only shows while you hold the stick, unless you choose otherwise.
• It only redraws the parts that change, so it stays fast.

Building

• Easy place (on by default, H): right-click a ghost to place exactly that block, facing the right way, even in mid-air. It takes the block from your inventory. It works in survival, on normal servers too.
• Auto place (off by default): missing blocks near you place themselves from your inventory. 4 blocks a second by default, up to 20.
• AutoBuild: if your linked chests hold everything, the server builds it for you, like Create's Schematicannon. You choose the speed, the order and what it may replace. It needs BlockCompanion on the server (singleplayer always has it).
• Middle click a ghost to pick its block.
• Info panel: shows the schematic, a progress bar, the layer, and how many of the block in your hand are left.
• HUD editor: move, resize or hide the panels.
• Material helper: holding a block shows the nearest ghosts that need it.
• Small celebrations: sparkles, a message when a layer is done, and fireworks when the build is finished. You can switch each one off.

Layers

• PgUp / PgDn move up and down through the levels of a build.
• Insert switches between "everything up to this level" and "this level only".
• V changes what you see: everything, up to this layer, this layer only, or hidden.

Undo and redo

• Ctrl+Z undoes and Ctrl+Y redoes moves, turns, locks and layer changes.

Resources and chests

• N opens the resource list. It shows what the build needs, what is placed, what you carry and what is in your chests.
• Link chests: hold the stick and Ctrl+right-click a chest, barrel or shulker box. Its items then count towards your materials.
• On a BlockCompanion server, easy place can take blocks straight from your linked chests.

Live link to BlockDesigner

Run BlockDesigner with its BlockCompanion Plugin (1.2.0 or later) on the same computer, and the game and the app connect.

• Send the project you are working on into the game.
• See the game update as you edit in BlockDesigner.
• Open a placed schematic in BlockDesigner to edit it.
• See your build progress and chest contents in the app.
• The plugin can also install the latest BlockCompanion into your game for you.

Servers

• Share, upload and lock schematics on one server, on Fabric and NeoForge (with the mod) or Paper (with the plugin).
• Server owners can switch off easy place, auto place and AutoBuild, and limit who uses AutoBuild.

Settings

• One settings screen for ghosts, building, the HUD, effects, colours, keys and BlockDesigner. Changes apply straight away.
• Change every colour, including a colour-blind safe preset.
• Rebind every key.

Privacy

• BlockCompanion never downloads anything and never sends your data over the internet. Update it from this page.
• The link to BlockDesigner only works on your own computer, and only with a secret code.
• It writes a few small files to ~/.blockcompanion so BlockDesigner can find the game. Your schematics stay in <game folder>/blockcompanion/schematics.

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Controls

You can change every key in Options > Controls > BlockCompanion or on the settings screen.

Key	Action
B	Schematic screen
N	Resource list
V	Change the view
PgUp / PgDn	Layer up / down
Insert	One layer / build up
M	Mirror (stick in hand)
Y	Lock / unlock
H	Easy place on / off
K	Mark a corner
O	Save the selection as .schem
Ctrl+Z	Undo
Ctrl+Y or Ctrl+Shift+Z	Redo
Middle click on a ghost	Pick its block

With the stick in hand, looking at a schematic:

Input	Action
Shift+scroll	Move it one block
Ctrl+scroll	Turn it 90 degrees
Ctrl+Shift+scroll	Switch between Move and Mirror
Alt+left-click / Alt+right-click	Selection corner 1 / 2
Shift+right-click	Clear the selection
Ctrl+right-click a chest	Link / unlink it

Normal scrolling still changes your hotbar, and the stick never breaks the block you click.

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Links

• Source code: github.com/doolecg/BlockCompanion
• Report a problem: github.com/doolecg/BlockCompanion/issues
• BlockDesigner: github.com/doolecg/BlockDesigner

BlockCompanion is open source under the MIT license.