Introduction

This page is for collecting information about characters on the web, and for trying to line up the concepts with USD.

Well established technologies are linked here for reference, and the concepts used by characters on the web are listed.

Concepts

• Linear Blend Skinning
• Blend Targets
• Animated Texture Maps
• Proceduralism
  • Look At
  • SpringBones
  • Cloth
  • Hair
  • Collision
    • Spheres
    • Cylinders
    • Planes
• Animation Clips
• Weighted and Blended Animation Clips
• Accessories
• Skins
• Clothing

Concepts, In Detail

Blend Targets

In Unity it's an import choice to either import or calculate blend shape normals. Calculation is then "auto-smooth" per-blendshape and the calculated normals are used at runtime for interpolation.

Video of a box/sphere blend shape interpolation:

https://academysoftwarefdn.slack.com/archives/C013Z5AMT7T/p1699372600728409?thread_ts=1699305453.565659&cid=C013Z5AMT7T

Which means that sharp cube to smooth sphere is representable in Unity and also in FBX and glTF. Hree's a glb file that illustrates the concept:

cubeToSphere.glb

Mapping the Concepts to USD

Anyone available to have a go?

VRM

Next Gen Idol Master Graphics and Animation Programming Preview; https://cedil.cesa.or.jp/cedil_sessions/view/416

• From CEDEC 2010, the basics of what's in VRM are laid out

Kawaii Physics; https://github.com/pafuhana1213/KawaiiPhysics/blob/master/README_en.md

• Widely used in Japanese AAA games plugin for UE that implements secondary character animation

vrm-samples, https://github.com/madjin/vrm-samples

• VRoid sample models in VRM format

VRMToybox, https://github.com/Keshigom/VRMToybox

• browser based VRM viewer

VRM4U, https://github.com/ruyo/VRM4U

• VRM importer for UE4

VrmEditor, https://github.com/ousttrue/VrmEditor

three-vrm, https://github.com/pixiv/three-vrm/tree/dev

• reference implementation

VRM specification, https://github.com/vrm-c/vrm-specification

• specification

VRM consortium, https://github.com/orgs/vrm-c

• hosting for their various projects, including the specification

VRM documentation, https://vrm.dev/en/

• documentation published by the consortium