Actinium - Vintage Optimization

Actinium

Modern rendering and Iris-style shaders for Minecraft 1.12.2 — without breaking the mods you already run.

Actinium is a mod for Minecraft 1.12.2 that makes your old client look and feel a lot more modern. It brings an Iris-style shader pipeline (the same kind of tech used by newer Minecraft shader mods) to 1.12.2, so you can run beautiful shader packs on a classic version — while keeping all your favorite 1.12 mods working alongside them.

What does it do?

• Modern shader packs on 1.12.2 — Run shader packs like MakeUp, BSL, Complementary, Bliss and more, with proper shadow, water, weather and post-processing support.
• Better terrain rendering — A rebuilt chunk rendering pipeline based on Celeritas for smoother, more efficient world rendering.
• Modern OpenGL handling — Cleaner state management under the hood, which means fewer weird rendering glitches when mods and shaders interact.
• Plays nice with your mods — Built around compatibility: classic 1.12 mods, entity rendering, GUI, and modded content are handled with care so they keep working with shaders on.

Who is this for?

• Players who love 1.12.2 modpacks but want modern shaders on top.
• Pack developers who want shader support without dropping classic mods.
• Anyone curious about what 1.12.2 can look like with a fresh rendering pipeline.

Requirements

• Minecraft 1.12.2
• Cleanroom Loader (required — this mod does not work with the old Forge alone)
• Java 21 or newer
• A GPU that can handle shader packs (the same as OptiFine shaders)

How to install

1. Install Minecraft 1.12.2 with Cleanroom Loader (follow Cleanroom's own setup guide).
2. Drop the Actinium-<version>.jar into your mods/ folder.
3. Optional: put shader packs in shaderpacks/ and pick one in the in-game shader menu.
4. Launch and enjoy!

Is it stable?

Actinium is in early alpha — it works, and a lot of testing has gone into it, but you may still hit rough edges. Shader packs and mods behave differently depending on versions, drivers and settings, so treat it as a "try it and see" project rather than a guaranteed one-size-fits-all solution.

Verified so far: MakeUp, BSL, Complementary Reimagined/Unbound, Bliss, iterationT, iterationRP (on the tested versions listed in the compatibility matrix). Some packs (e.g. SEUS PTGI HRR) currently fail to enable — pack support is an ongoing effort.

Note on AI-generated code

Nearly all code in this project is produced with AI coding agents, and changes may also be reviewed by AI (human-in-the-loop): every change is reviewed, tested and regression-verified by humans and AI before it is merged. If you prefer to avoid AI-generated code, feel free to look for alternative projects; if you have any concerns, reach out via issues.

Third-party code

Actinium is built on top of several open-source projects. Code from these projects (and the compatibility work around it) remains under each upstream project's original license:

• Celeritas — chunk building, uploading, culling and terrain drawing (embedded as a Gradle subproject)
• GLSM — OpenGL state tracking, redirection and fixed-function pipeline simulation
• GTNHLib — rendering primitives, buffers, post-processing and legacy rendering utilities
• Iris — the shader pipeline structure, pack parsing and GLSL transformation this project adapts
• GLSL Transformation Library — GLSL parsing and transformation
• Sodium / Embeddium — performance-oriented rendering design and the option framework
• Angelica / GTNH ecosystem — references for 1.7/1.12-era shader compatibility and legacy OpenGL behavior

A full list of sources and licenses lives in THIRD_PARTY_NOTICES.md in the repository.

Links

• Source code & issues: github.com/DHJComical/Actinium
• Compatible with: Cleanroom Loader, Distant Horizons (partial), and many more (see the compatibility matrix in the repo)