Avatar Format Guide

March 20, 2025 · View on GitHub

What is VRM?

VRM is an open file format for 3D humanoid avatars, perfect for VR and the metaverse. Think of it as a universal format for 3D characters that works everywhere!

📋 Quick Requirements

  • File format: .vrm
  • Max file size: 25MB recommended
  • Polygons: 20,000 or less recommended
  • Textures: 2048x2048px max per texture
  • Bones: Standard humanoid skeleton

✅ Checklist Before Sharing

  • Model is rigged with humanoid skeleton
  • Textures are properly packed
  • No copyright material included
  • Tested in VRM viewer
  • File size is optimized

🔍 Technical Details

Standard Bone Structure

- hips
  |- spine
  |  |- chest
  |     |- upperChest (optional)
  |        |- neck
  |        |  |- head
  |        |     |- leftEye
  |        |     |- rightEye
  |        |     |- jaw (optional)
  |        |
  |        |- leftShoulder
  |        |  |- leftUpperArm
  |        |     |- leftLowerArm
  |        |        |- leftHand
  |        |           |- leftThumbProximal
  |        |           |  |- leftThumbIntermediate
  |        |           |     |- leftThumbDistal
  |        |           |
  |        |           |- leftIndexProximal
  |        |           |  |- leftIndexIntermediate
  |        |           |     |- leftIndexDistal
  |        |           |
  |        |           |- leftMiddleProximal
  |        |           |  |- leftMiddleIntermediate
  |        |           |     |- leftMiddleDistal
  |        |           |
  |        |           |- leftRingProximal
  |        |           |  |- leftRingIntermediate
  |        |           |     |- leftRingDistal
  |        |           |
  |        |           |- leftLittleProximal
  |        |              |- leftLittleIntermediate
  |        |                 |- leftLittleDistal
  |        |
  |        |- rightShoulder
  |           |- rightUpperArm
  |              |- rightLowerArm
  |                 |- rightHand
  |                    |- rightThumbProximal
  |                    |  |- rightThumbIntermediate
  |                    |     |- rightThumbDistal
  |                    |
  |                    |- rightIndexProximal
  |                    |  |- rightIndexIntermediate
  |                    |     |- rightIndexDistal
  |                    |
  |                    |- rightMiddleProximal
  |                    |  |- rightMiddleIntermediate
  |                    |     |- rightMiddleDistal
  |                    |
  |                    |- rightRingProximal
  |                    |  |- rightRingIntermediate
  |                    |     |- rightRingDistal
  |                    |
  |                    |- rightLittleProximal
  |                       |- rightLittleIntermediate
  |                          |- rightLittleDistal
  |
  |- leftUpperLeg
  |  |- leftLowerLeg
  |     |- leftFoot
  |        |- leftToes
  |
  |- rightUpperLeg
     |- rightLowerLeg
        |- rightFoot
           |- rightToes

Note: Bones marked as (optional) are not required but recommended for better compatibility and animation support.

Required vs Optional Bones

Required Bones:

  • Hips and main body structure
  • Basic arm and leg chains
  • Head and neck
  • Basic hand structure

Optional but Recommended:

  • Finger bones (for hand animations)
  • Eye bones (for look-at features)
  • Toe bones (for foot animations)
  • Upper chest (for better upper body movement)
  • Jaw (for facial animations)

Supported Features

  • Facial expressions
  • Look-at tracking
  • Auto blink
  • Lip sync
  • Physics (hair, clothes)

🎯 Best Practices

  1. Optimization

    • Use texture atlasing
    • Minimize bone count
    • Optimize mesh topology

  2. Compatibility

    • Test in multiple platforms
    • Verify animations work
    • Check texture compression

  3. Quality

    • UV maps are clean
    • No overlapping vertices
    • Proper weight painting

📚 Resources