Avatars in Virtual Community

How to process and import Mixamo characters and skins for Virtual Community simulator

Published: 6/20/2025 Last updated: 6/20/2025
By Virtual Community Team

This page explains how to process and import avatar skins into Virtual Community using Mixamo or Avatar SDK, and lists the supported avatar actions and APIs.

Mixamo Avatar Skins

1. Download FBX model from Mixamo

  • Go to Mixamo, choose your character.
  • Download as FBX Binary (.fbx) in T-pose.

2. Process FBX model with Blender

a. Import the FBX Model

  1. Open Blender.
  2. Select File -> Import -> FBX (.fbx) and choose your downloaded file.

b. Merge Meshes (if multiple)

  • In Blender’s Outliner or 3D Viewport, select all mesh objects (hold Shift).
  • Right-click and select Join (Ctrl+J).
  • (Skip if only one mesh.)

c. Reduce Polygon Count

  • Select merged mesh.
  • Go to Modifiers, add Decimate modifier.
  • Set Collapse ratio to 0.15 ~ 0.2 to bring face count to ~4k–6k.

d. Export to GLB

  1. Go to File -> Export -> glTF 2.0 (.glb/.gltf).
  2. Ensure:
    • Uncheck Transform -> +Y Up
    • Check Geometry -> Apply Modifiers
    • Uncheck Animation -> Animation and Shape Keys
  3. Save as .glb.

e. (Optional) Reduce Texture Resolution

  • Use gltf-transform to lower texture size for performance: 
    gltf-transform resize --width 1024 --height 1024 input.glb output.glb

3. Troubleshooting

”IndexError: index X is out of bounds for axis 0…”

  • Example error: 
    IndexError: index 194 is out of bounds for axis 0 with size 65
  • Solution: Open and re-save the GLB with a 3D viewer such as Gestaltor to ensure a clean joint index mapping.

Skin & Motion Joint Mismatch

  • When exporting motion FBX from Mixamo, choose a standard human rig such as “Jackie” or “Michelle” for best compatibility.

Avatar SDK Skins

Coming soon. We will provide step‑by‑step instructions for generating a personalized avatar with Avatar SDK.

Load Avatars in Virtual Community

When loading avatars in the simulator, you will use the following parameters:

  • motion_data_path: Path to motion .pkl
  • skin_options:
    • glb_path: Your exported .glb file
    • euler, pos: (For pose/orientation; optional or advanced)
  • ego_view_options: (Optional)
    • res, fov
  • frame_ratio: Frame update ratio (for stepping)
  • terrain_height_path: (Optional; auto-height support)

Supported Avatar Actions

Core movement and interaction

  • Move forward: move(distance[, speed=1])
  • Turn left: turn_left(angle[, turn_frame_limit=15])
  • Turn right: turn_right(angle[, turn_frame_limit=15])
  • Reach (touch/press): reach(hand, object)
  • Pick: pick(hand, object)
  • Put: put(hand[, position, rotation])
  • Throw: throw(hand[, orientation])
  • Open: open(hand, object)
  • Close: close(hand, object)
  • Sit: sit([object, position])
  • Stand up: stand_up()
  • Drink: drink(hand)
  • Eat: eat(hand)
  • Play: play(hand, duration)

Vehicle interactions

  • Bus: enter_bus(bus), exit_bus()
  • Bicycle: enter_bike(hand_id, bike), exit_bike(hand_id)
  • Car: enter_car(hand_id, car), exit_car(hand_id)

Avatar APIs

  • reset(global_trans, global_rot)

  • spare(): Return True if avatar is idle

    • from ViCo.modules.avatar.utils import ActionStatus

  • get_global_xy()

  • get_global_height()

  • get_global_pose(): Returns [x, y, z, r, p, y]

  • set_global_height(height)

  • render_ego_view(rotation_offset, depth, segmentation)

Adding Your Own Motions

  1. Download motion FBX into: Genesis/genesis/assets/motions/

  2. Convert to pickle:

    python tools/misc/convert_fbx.py -e Genesis/genesis/assets/motions/ -o Genesis/genesis/assets/motions/

  3. Add your motions under: Genesis/genesis/assets/avatars/motions