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Vivecraft for Minecraft 1.12

This readme is intended for developers. For downloads and gameplay instructions please see the official website

Using this Repository

Vivecraft uses patches to avoid distributing Minecraft code. The build scripts are in Python 2.X.

  • Fork, checkout or download the repo using your Git method of choice.
  • Install Java JDK 1.8. The Java JRE will NOT work.
  • Set the JAVA_HOME environment variable to the JDK directory
  • Add %JAVA_HOME%\bin to your PATH environment variable
  • Install Python 2.7.x (NOT 3.x). Be sure to tick the 'add python to your PATH' option during install. Download from
  • Open a command prompt and navigate to the repo directory
  • Run install.bat

The install process ( does a number of things:

  • It downloads MCP (Minecraft coder's pack) and extracts it to the \mcp9xx\ directory.
  • It downloads a ton of dependencies.
  • It merges Optifine into vanilla minecraft jar.
  • It decompiles and deobfuscates the combined minecraft/optifine into \mcp9xx\src.minecraft_orig_nofix\
  • It applies any patches found in \mcppatches\ and copies the result to\mcp9xx\src.minecraft_orig\
  • It applies all the patches found in \patches\ and copies the result to \mcp9xx\src\minecraft.
  • It copies all code files found in \src\ to \mcp9xx\src\minecraft.
  • It copies all files found in \assets\ to \mcp9xx\src\assets. This directory is now the full 'Vivecraft' codebase.

If you use Eclipse you can open the workspace found in \mcp9xx\eclipse. You will have to correct the library path for the vanilla jar and realms jar, and also add libraries for JRift, json, asm, and launchwrapper, all of these can be found in the root /lib folder. To run the game from eclipse you also have to attach natives to the lwjgl jar (from lib/natives).

Make all changes to the game in the \mcp9xx\src\minecraft directory.

To update code to Github:

  • run getchanges.bat. This compares mcp9xx\src\minecraft to mcp9xx\src\minecraft_orig. patches are generated for modified files and copied to \patches. Whole new files are copied to \src.
  • Push to Github.

To build an installer:

  • run build.bat. This runs getchanges, build, and then create_install. Basically it takes the new files and patches and creates a jar. And then it uses the code and jsons found in \installer\ to make an installer.exe.

To update changes from github

  • After pulling changes from github run applychanges.bat. This backs up mcp9xx\src\minecraft to mcp9xx\src\minecraft_bak, and starts over by applying all patches in \patches\ to mcp9xx\src\minecraft_orig, and copies the result o mcp9xx\src\minecraft

Caveats - Maintaining Forge Compatibility

When Vivecraft is run with Forge, any public method can be called by any mod, and any vanilla class is up for grabs for ASM modification. To this end, please follow these guidelines in writing Vivecraft code:

  • Do not rename any vanilla methods, fields, or classes
  • Do not change the type or signatures of any vanilla members.
  • Keep modification to vanilla methods minimal, move code to your own methods, preferrably in your own files.

Additionally, vivecraft does not use bytecode manipulation at runtime to modify the vanilla classes (mostly), it replaces them wholesale in much the same way as optifine. It only replaces files that have been modified by the user, and it replaces them after Forge and Optifine have made their modifications to them. This means that any vanilla class you modify will NOT have any of Forge's code changes made to it at runtime. To fix this, the class must have all Forge's method calls added via reflection in Vivecraft. Optifine uses this method extensively and Vivecraft expands it.

Before making ANY changes to a vanilla class file you should check to see:

  • Is the class already modified by Vivecraft? You can tell if there is a .patch file for it on github. If so: feel free to make any other changes.
  • Is the class already modified by Optifine? You can tell because there will usually be calls to If Optifine has already made the Reflection calls, continue with your edits.
  • Is the class modfied by Forge? - Check Forge's github patches to see, Forge modifies many base classes but not all. If the class is not modified by Forge, feel free to edit it.
  • If the class is modified by Forge, and neither Vivecraft, nor Optifine have added the Reflection calls, you will have to do so along with your own changes. See for numerous examples.