body-models-viser 0.2.0

Browser-side body model evaluation for viser

body-models-viser

Browser-side body model evaluation for viser.

Python owns the body model asset loaders and the prepare_identity() / prepare_pose() calls. TypeScript owns the browser model lifecycle and WASM buffers. Rust owns the stateless forward_vertices() kernel.

Usage

Skinned Body Models

Use add_body_model() for non-rigid skinned body models such as SMPL, SMPL-X, MANO, FLAME, MHR, SKEL, ANNY, and SOMA.

import body_models_viser as bmv
import viser
from body_models.smpl.numpy import SMPL

server = viser.ViserServer()
model = SMPL(gender="neutral")
handle = bmv.add_body_model(server.scene, "/smpl", model, color=(173, 216, 230))

pose = handle.body_pose.copy()
pose[2, 0] = 0.5
handle.body_pose = pose

add_body_model() returns a model-specific handle with set_pose(...), remove(), global_rotation, global_translation, and the pose properties supported by that model.

Skeletons

Use add_skeleton() for a standalone clickable skeleton. It takes joint positions and a parent index for each joint.

import body_models_viser as bmv

pose = model.get_rest_pose()
skeleton = model.forward_skeleton(**pose)
joint_positions = skeleton[:, :3, 3]

handle = bmv.add_skeleton(
    server.scene,
    "/skeleton",
    joint_positions,
    model.parents,
    joint_names=tuple(model.joint_names),
)

handle.visible = True
handle.joint_positions = joint_positions

Rigid Body Models

Use add_rigid_body_model() for rigid articulated models that expose link_names, link_mesh(link_name), and forward_links(...).

import body_models_viser as bmv

handle = bmv.add_rigid_body_model(server.scene, "/robot", model)
handle.set_pose(body_pose=handle.pose["body_pose"])

The rigid-body helper renders one static mesh per link, then updates link transforms when the pose changes.

Runtime

bmv.add_body_model(scene, name, model) does three things:

1. Injects body-models-viser.js and body-models-viser.wasm.
2. Sends faces, material props, current identity, and current pose as little-endian binary buffers.
3. Returns a body model handle.

Every handle.set_pose(...) call sends prepared pose data. If identity-changing parameters such as shape, expression, or scale_params change, Python recomputes prepare_identity() and sends that identity again. TypeScript copies changed buffers into persistent WASM memory, calls the Rust forward_vertices() kernel, and forwards the resulting vertex buffer to viser as a regular mesh message.

The browser protocol is model-agnostic: Python adapts each model to a shared runtime payload containing skinning weights, rest vertices, skinning transforms, and pose offsets. Adding another body model should only require a Python preparation adapter when its body-models outputs need normalization.

Development

Build the Rust crate:

cargo test

Build the browser bundle and WASM:

cd client
npm test

The browser build requires a Rust toolchain with wasm32-unknown-unknown installed, for example:

rustup target add wasm32-unknown-unknown

Run the small visualizer:

uv run --no-sync scripts/visualize_models.py

Check NumPy/WASM vertex parity for all supported models:

uv run scripts/check_model_parity.py