Lodur

A physics character middleware for characters that feel and react: they pull back from something hot, jump when poked, and, if they want their objective badly enough, crawl toward it after losing a leg.

Status: design plus a first slice of layer 5. The design is docs/lodur-target.md; read it first. What runs today is a PD-muscle active ragdoll on Ymir's Box3D SoA world: docs/first-slice.md (measured and unmeasured). Layers 1-4 (perception, reflex, drive, behaviour) are not coded.

Entry points: src/Lodur.Core/PdMuscle.cs (engine-free PD law, strength per muscle), src/Lodur.Body.Ymir/HumanoidRagdoll.cs (the ragdoll and Drive), tests/Lodur.Tests (stand, fall, rest, same-seed-same-hash). Needs a sibling Ymir checkout at main (the SoA joints merge, 2026-11-10, or later); dotnet test tests/Lodur.Tests builds its native library with cmake.

The problem

Active-ragdoll middleware (NaturalMotion's Euphoria, RootMotion's PuppetMaster) and learned physics controllers (DReCon, ProtoMotions) solve the body: physics, pose tracking and, in the learned case, balance. None of them models the nervous system. They have no senses that are not forces, no reflexes layered under deliberate behaviour, and no character whose pain competes with its will over time. Lodur is that layer.

Shape (planned)

• Core (C#, no engine references): perception, reflexes, a drive state of pain, shock, adrenaline and resolve that evolves every tick, and behaviour selection that turns the drive into targets plus muscle strength.
• Body (per engine): follows those targets on the engine's own articulated physics. v1 is a PD-tracking active ragdoll in Unity; v2 adds a small learned tracker for upright balance behind the same interface.

First consumer

Bad Day Simulator, a 3D physics sandbox.

Where it lives

Canonical: https://eureka.gamecult.org/forge/GameCult/Lodur. GitHub GameCult/Lodur is a push mirror.

Prior-art research: gamecult-ops/docs/research/euphoria-at-home-prior-art.md.