MotionBench

Every AnimatedKit gait clip rebuilds its whole scene from the same code path at every phase, and every ParametricKit model rebuilds from the same code path at every slider value — so ShapeScene.Parts[i] at one sample and at another sample is the same logical part, just moved. Sample a handful of points along that axis, track each part's world-space bounding-box centre, and any part whose position spreads out past a small threshold is a candidate attachment point — a hook — found automatically, with zero changes to the recipe that built it.

The same detector works whether the axis is a gait phase (a walk cycle) or a full slider sweep (min→max on a bestiary monster's every knob at once) — which is how a technique built for 99 locomotion clips ended up covering all 1,719 sources the library has: every daemon, dragon, fiend, undead, aberration, outsider, fey and elemental in the bestiary that never got a hand-authored animation still has parts that move when its sliders move.

A detected hook — or any point on any model — can now be a mount for a real, weighted, bendable attachment instead of a rigid transform. MaterialPreset combines a cited density and Young's modulus (this repo's own Chemistry.Materials and building-materials catalogs) with an everyday-object cross-section to get a real flexural rigidity E·I — the actual reason aluminum foil is floppy despite aluminum being a structurally stiff metal: same E as a solid rod, but I ∝ thickness³ collapses at foil gauge. FlexibleAttachment then clamps a chain of real PhysicsAndAstronomy.Physics.SoftBody (XPBD) particles to a live parent position every step, each one pulled toward its "straight rod" position by a spring sized from that E·I, weighted by real mass, and — the "memory" dial — creeping its own rest target toward wherever gravity or a knock left it, at a rate set by the material's plasticity.

Shapes.Coil sweeps a wire along a sampled helix — a tight spring, a wide slinky, a long coil, or a chunky bedspring, all from the same four sliders. SpringPreset derives a shear modulus G = E/(2(1+ν)) from a cited material's Young's modulus and Poisson's ratio (no repo catalog has shear modulus directly — this is the standard isotropic- elasticity relation, not an invented number), then the classic helical-spring formula k = G·d⁴/(8·D³·N) for the actual spring constant. A mass hung on one of these springs settles at the textbook Hooke's-law equilibrium — proven, not assumed.

Mounting an existing catalog model on a material needed no new code at all — FlexibleAttachment's tip position was already public, so any of the 1,719 sources swept above can hang, sway, or spring from a chosen material the same way a synthetic rod does.

Everything above composes into an editable system: a Craft is a KSP-style part tree — pick a core, slap on an evenly-spaced ring or freehand slots, link parts onto parts to any depth, re-parent, remove subtrees — with every edit validated the moment it's made (duplicate ids, dangling parents, and re-parent cycles all throw). Parts carry time-driven actions: spin, oscillate, pulse, and Detach — real staging, where a booster and its whole subtree freeze their pose at the staging instant and fall ballistically (y = h − gt²/2, verified against hand-derived numbers in the KATs). A craft saves to a ~2 KB plain-text .craft file you can read, diff, and hand-edit — and loading goes through the same validated editing API, so a corrupt file fails loud at load, never as a silently-wrong render.