Physics, constraints, menus and motion

PhysBones, VRM spring bones and Dynamic Bone become Basis jiggle physics, VRChat and VRM constraints become their Basis equivalents, the avatar descriptor and head chop become BasisAvatar and BasisHeadChop, menu toggles and VRM expressions are rebuilt as HVR Vixxy controls, and animation that plays on its own becomes authored motion.

Read by component, not by platform

An avatar is read for the components it carries, so one using nothing but Dynamic Bone converts as readily as a VRChat avatar or a VRM. Clothing and accessories are prefabs of their own and are read as such; any of them can be left out.

Approximations reported

Anything approximated or dropped is reported with a reason before anything is written, under a stable code. One undo reverts the components a conversion wrote.