Litematica Mod 1.16.5/1.15.2 is a new schematic mod created from scratch and is targeting light (client-side) mod loaders like LiteLoader on 1.12.x, Rift on 1.13.x and Fabric 1.14+.
How to use:
The default hotkey to open the in-game config GUI is M + C. If you are for example on AZERTY keyboard layout instead, then the keys are different, and M + C becomes, + C instead, etc.
Note: If you have Optifine installed, then there are some options that you most likely will need to disable in Optifine HD, or otherwise it will break the schematic rendering:
Render Regions needs to be disabled
Shaders need to be set to OFF, or alternatively disable VBOs in the vanilla Video settings, and disable both the ‘schematicOverlayModelOutline‘ and ‘schematicOverlayModelSides‘ options in the Visuals category
Fast Render might also need to disable if there is still some weird HUD/GUI rendering issues.
The main feature of a schematic mod is to display a “hologram” version of a structure, which shows you exactly how to build the structure and where to place the blocks. It also includes a (configurable) overlay to highlight missing, extra or wrongly placed blocks.
Litematica also includes a nice Material List, including a Material List HUD, to help you collect the materials needed for the build.
There is also a Schematic Verifier feature, including an overlay, which you can use to scan the entire schematic area and look for any mistakes. This can be extremely useful especially with technical/redstone builds, where tiny mistakes can break everything.
There are also several Creative-mode-only helper features, such as Fill, Replace, Delete and also a Paste mode for “pasting” schematics into the world (immediate/direct in single player, using /setblock commands in multiplayer).
If you have Optifine installed, then there are some options that you most likely will need to disable in Optifine, or otherwise it will break the schematic rendering:
If you get glitchy weird triangles, then set shaders to OFF (not Internal) and restart the game. I’m not sure why this is broken for so many people, but it works for some, and it also works fine for myself… so debugging it is kind of impossible since it works for me to begin with.
Render Regions probably needs to be disabled to prevent weird rendering issues (the schematic (partially?) rendering in weird places)
Fast Render might also need to be disabled if there are still some weird HUD/GUI rendering issues