BuiltIn — Constructor & Blueprint Paper

NeoForge · Minecraft 1.21.1

BuiltIn adds the Constructor block: preview structures in a GUI, place a ghost build in the world, rotate and offset it, then construct block-by-block with a clear materials list (technical / unobtainable blocks are filtered out).

It also adds Blueprint Paper to capture areas from the world or share structures between players (client-side library). On first install, vanilla village house templates can be copied into your config folder so you always have blueprints to start from.

Constructor GUI — preview & materials

Ghost placement
Ghost preview in the world

Features

Constructor GUI with 3D preview, ghost placement, rotation, offsets, confirm/cancel.
Materials panel — sorted counts; filters out jigsaw, structure blocks, barriers, and blocks without survival items.
Vanilla village structures — templates can be populated under your config folder from the game’s structure manager.
Custom structures — add .nbt files manually or create them in-game with Blueprint Paper.
Per-player client lists for player-made structures (stored under config on disk).
Delete user-added structures from the Constructor GUI (user_* only).

Adding structures — two ways

1) Via config folder (manual / modpack-friendly)

Open your Minecraft instance config folder.
Open config/builtin/Structure/
Add valid Minecraft structure files: *.nbt (structure-block / exported template format).
Files named user_* are treated as player-added blueprints (removable with ✕ in the GUI). Other .nbt files are normal library entries.
Restart or open the Constructor — blueprints reload from that folder. On a dedicated server, opening the Constructor ensures templates are refreshed before the GUI opens.

Tip: Ship extra .nbt files with a modpack so players get structures without using Blueprint Paper.

2) In-game — Blueprint Paper

Hold Blueprint Paper.
First right-click a block → corner A (confirmed in the action bar).
Second right-click a block → corner B. Must be on the same Y as A (flat rectangle for the floor plan).
Set height on the screen (live preview), then Add.
Writes a user_* .nbt under config/builtin/Structure/ on your client and fills the paper with structure data.
Import: with a filled paper, right-click the Constructor to add the blueprint to your client list.
Shift + right-click → reset corners and clear stored blueprint data.

Empty paper shows “Empty blueprint paper” in the tooltip; filled paper has an enchant-style glint. Trade papers like items — each player imports into their own client folder.

Vanilla village bootstrap

The mod can copy vanilla village house templates into config/builtin/Structure/ when appropriate, so the Constructor isn’t empty on first use.

Requirements

Minecraft 1.21.1
NeoForge (match your loader version)

FAQ

Why no barriers / structure blocks in materials?
Filtered for survival-friendly builds.

Second paper click ignored?
Corner B must match corner A’s Y level.

Where are files stored?
config/builtin/Structure/ on the client machine.

Mod ID: builtin · BuiltIn

Build In