Live2D

The artist delivers the picture split into layers — eyes, hair, mouth, face — and in the Cubism editor each part gets meshes and deformers laid over it. Parameters such as "angle X" or "mouth open" drive how the meshes bend, and the runtime interpolates between key poses. It reads as a 3D rotation while keeping the illustration's linework, something rigged 3D rarely manages.

It spread first through Japanese mobile games and visual novels, where a character would otherwise have been a still image. Then came VTubers, wiring those parameters to webcam face tracking, and a niche tool for game animators quietly became the infrastructure of an entire entertainment genre.