InstantWorldMirror - Instant World Mirror

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Instant Sandbox - Explore Without Consequences

InstantWorldMirror provides Minecraft players with an instant sandbox testing ground. Using the Dimension Mirror, you can create a mirror copy of the surrounding area at any location, freely explore, test, and experiment without worrying about any impact on the original world.

Core Use Cases

Mod Testing: Test new mod functionality and compatibility in the mirror world without risking your main save
Redstone Debugging: Copy your redstone contraptions for repeated testing and debugging without teardown costs
Adventure Scouting: Explore dangerous areas in the mirror first to plan safe routes before venturing in
Building Design: Preview building plans in the mirror, then build in the main world once satisfied
Server Events: Provide safe activity spaces for players, with automatic cleanup after events

Features

Dimension Mirror

The Dimension Mirror is your key to the mirror world:

Right-click any solid block to create an entry portal
Supports Efficiency enchantment to reduce cooldown (20% reduction per level)
No cooldown in Creative mode
Supports creating mirrors from Overworld, Nether, End, and mod-added custom dimensions

Mirror World Mechanics

Copies terrain within a configurable radius centered on the portal (default 10 chunks, configurable 1-32 chunks)
Complete copying of blocks, block entities, biome data, and structure information
Optional entity copying (mobs, decorations, etc.)
Automatic synchronization of source world weather and time
Natural mob spawning disabled by default, can be enabled via commands or config

Multiplayer Support

Supports up to 8 parallel mirror dimensions, allowing multiple players to use their own mirror worlds simultaneously
Multiple players can enter the same mirror session through the same portal
Comprehensive permission system for server admins to control player access and item transfer rules
Mirror world automatically enters cleanup when all players leave

Portal System

Entry portal opens after world copy completes, lasts 5 minutes by default (configurable)
Return portal in mirror world is permanent by default
Use Dimension Mirror in mirror world to create return portal
Automatic return to source world upon death

Performance Optimization

Heightmap scanning technology skips air columns, significantly reducing unnecessary copying
Section-level operations instead of block-by-block processing
Sequential queue processing to avoid server overload
Smart cleanup mechanism only processes modified chunks

Installation

Install NeoForge 1.21+
Download this mod JAR file
Place in .minecraft/mods folder
Launch the game

Crafting Recipe

[Glass]    [Obsidian] [Glass]
[Obsidian] [Ender Pearl] [Obsidian]
[Glass]    [Obsidian] [Glass]

Commands

All commands start with /iwm:

Command	Description	Permission
`/iwm return`	Force return to source world	All players
`/iwm mob on/off/status`	Control mirror world mob spawning	OP (Level 2)
`/iwm allow <player>`	Allow player to use mirror feature	OP (Level 2)
`/iwm deny <player>`	Deny player from using mirror feature	OP (Level 2)
`/iwm itemtransfer <player> <true/false>`	Control player item transfer permission	OP (Level 2)
`/iwm status`	View dimension pool status and player info	OP (Level 2)
`/iwm forceclear <dimension>`	Force clear specified mirror dimension	OP (Level 3)
`/iwm purge`	Completely delete all mirror world saves (requires restart)	OP (Level 3)

Configuration

Config file located at config/instantworldmirror-common.toml

Dimension Pool Settings

Config	Default	Description
dimensionPoolSize	4	Mirror dimension pool size (1-8), determines max concurrent mirror sessions

World Copy Settings

Config	Default	Description
copyChunkRadius	10	Copy radius (chunks), total chunks = (radius*2+1)^2
copyChunksPerTick	2	Chunks copied per tick, higher = faster but may cause lag
cleanupChunksPerTick	4	Chunks cleaned per tick
edgeCleanupRadius	3	Extra radius for BFS edge cleanup scan

Portal Settings

Config	Default	Description
entryPortalLifetime	300	Entry portal duration (seconds), -1 for permanent
returnPortalLifetime	-1	Return portal duration (seconds), -1 for permanent
maxPortalLoadingTime	600	Maximum portal loading wait time (seconds)

Item and Mob Settings

Config	Default	Description
allowItemTransfer	false	Whether to allow players to bring items back by default
mirrorCooldown	300	Dimension Mirror cooldown (seconds), reduced by Efficiency
copyEntities	false	Whether to copy mob entities
copyDecorationEntities	true	Whether to copy decoration entities (paintings, item frames, etc.)
enableMobSpawning	false	Whether to allow natural mob spawning in mirror world

Environment Settings

Config	Default	Description
copyBiomes	true	Whether to copy biome data
copyStructures	true	Whether to copy structure data
copyHeightmaps	true	Whether to copy heightmap data

Server Limits

Config	Default	Description
maxMirrorWorldsPerPlayer	1	Maximum concurrent mirror sessions per player
staleSessionCleanupInterval	300	Stale session cleanup check interval (seconds)

Client Settings

Client config located at config/instantworldmirror-client.toml

Config	Default	Description
showCooldownHud	false	Show cooldown timer HUD in top-left corner

Gameplay

Craft a Dimension Mirror
Go to the area you want to copy
Right-click a solid block to create an entry portal
Wait for world copy to complete (portal animation indicates loading state)
Enter the portal to start exploring and experimenting in the mirror world
Use Dimension Mirror to create a return portal, or use /iwm return command
Mirror world automatically cleans up after you leave, ready for next use

Important Notes

By default, items obtained in the mirror world are NOT kept when returning
Cannot build Nether or End portals in the mirror world
Each new mirror session copies the world fresh
Changes in mirror world do NOT affect the source world
Server admins have full control over player access permissions

Downloads

CurseForge - Mod download
GitHub - Source code

License

Apache License 2.0