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An AI agent figures out how a Lego model moves
ldraw-mecha hands an AI coding agent the official LDraw source file of a Lego set and has it work out how the model's gears, hinges and pistons actually move, then write the Blender animation itself. A solo developer built it after people asked whether his earlier Lego-building tool could also animate models.
ldraw-mecha describes itself plainly: "Give an LDraw LEGO model to an AI agent, get back a Blender-animated version of it." LDraw is a decades-old open text format for describing Lego models: a plain file listing parts and their positions, no pictures involved. The author had already built a related tool, ldraw-nova, which has an agent assemble LDraw models from scratch, and after that people asked whether the same approach could animate a model instead. It turned out it could: by adding specific annotations to a model's source file, an agent learns not just how the model is built but can work out how one of its mechanisms, say a truck's crane or a plane's landing gear, actually moves. The model is then converted into a 3D file for Blender carrying the same annotations, and the agent writes the Python scripts that animate the mechanism it identified: a crane lifts, a plane extends its gear and lands. The author tested the process with Claude Sonnet 5.5, Claude Opus 5.5 and Claude Haiku 5.5, and says the results were "pretty good and consistent" but not perfect — large models still have to be simplified down to one mechanism rather than the whole build.
Why a vibe-coder should care
This is not an everyday tool, it is a demonstration that an AI agent can be taught to read someone else's mechanical design and predict how it moves, not just write code. For Lego Technic hobbyists or anyone teaching agents to work with Blender and 3D files, it is a working process and a handful of sample projects to start from instead of figuring it out from zero.
How to install
Copy this and send it to your agent — Claude Code, Codex, any of them:
Set up ldraw-mecha from https://github.com/anteloc/ldraw-mecha following its README (macOS only for now), pick one of the pre-annotated sample models, and ask the agent to work out its mechanism and animate it in Blender — show me the resulting video.
Needs a Mac (Linux and Windows are untested so far) — no dedicated graphics card required, but you'll install Blender, LeoCAD and the project's own toolset, which takes more than one command.
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