galaw - A Rust-based kinematics library

galaw (pronounced gah-LOW, rhymes with "cow") is the Tagalog word that means movement or motion. This library is for computing kinematics.

Features

• Stateless — compute_fk takes joint commands, returns fresh poses. No mutable state, no setup step, safe to call concurrently.
• Code-generated (optional) — ahead-of-time compute_fk per robot, no parsing or Result on the hot path, ~1.6-4.5x faster than runtime.
• Correctness-tested — checked against k across randomized joint configs within limits.
• Named lookups — command joints/links by name, never by assumed index.
• Descriptive errors — malformed URDFs fail with a specific cause, not a panic.

Quick Start

galaw has two APIs for computing forward kinematics, with different performance/flexibility tradeoffs:

• Runtime — parses a URDF at runtime, works with any robot.
• Generated — ahead-of-time code generation, fixed to one robot at compile time. ~1.6-4.5x faster, no parsing or Result handling on the hot path.

Runtime

use galaw::{error::GalawError, load_urdf, types::GalawModel};

fn main() -> Result<(), GalawError> {
    let model: GalawModel = load_urdf("assets/urdf/custom/simple_arm_2dof.urdf")?;

    // Command each actuated joint by name — never by assumed position.
    let mut joint_cmds = vec![0.0; model.num_actuated_joints];
    let shoulder_idx = model.get_joint_idx("shoulder_joint").expect("shoulder_joint exists in URDF");
    let elbow_idx = model.get_joint_idx("elbow_joint").expect("elbow_joint exists in URDF");
    joint_cmds[shoulder_idx] = 0.5;
    joint_cmds[elbow_idx] = -0.3;

    let poses = model.compute_fk(&joint_cmds)?;
    println!("{:?}", poses);
    Ok(())
}

Full runnable version: examples/runtime_fk.rs — cargo run --example runtime_fk

Generated

Ahead of time, generate fixed FK code for a specific robot (code for the robots shipped with this repo already exists under src/generated/ — see galaw::generated):

# 1st arg: urdf_path, 2nd arg: out_path
cargo run --bin codegen_kinematics -- assets/urdf/custom/simple_arm_2dof.urdf src/generated/simple_arm_2dof.rs

Then call the generated function directly — no GalawModel, no Result, no parsing at call time:

use galaw::generated::simple_arm_2dof;

let joint_cmds: [f64; 2] = [0.5, -0.3];
let poses = simple_arm_2dof::compute_fk(&joint_cmds);

Full runnable version: examples/generated_fk.rs — cargo run --example generated_fk

Which one should I use?

Runtime if you need to support arbitrary URDFs at runtime — e.g. a robot chosen by a user, or loaded from a file you don't control at compile time. Generated if you know the robot ahead of time and want the fastest possible FK, at the cost of a codegen step and one generated file per robot.

Performance

galaw outperforms k overall. Averaged (geometric mean) across the four benchmarked robots: galaw-runtime is ~3.3x faster than k, and galaw-generated is ~8.9x faster than k.

Benchmarked on: Intel Core i7-10750H @ 2.60GHz (6C/12T, boost up to 5.0GHz), 16GB RAM, Ubuntu 22.04.5 LTS (kernel 6.8).

Reproduce with cargo bench followed by cargo run --release --example plot_bench (see benches/fk_speed.rs / examples/plot_bench.rs).

Attributions

This repository incorporates robot descriptions (URDF files) from various open-source projects. Each is used in compliance with its original license:

Note: these robots' visual/collision mesh files (STL/DAE geometry) have been removed from this repo since galaw only parses a URDF's kinematic structure. The URDF files still reference meshes/... paths for compatibility with other tools. If the actual mesh geometry is needed, get it from the original project linked below.

• Enlight-L (Flexiv) – Derived from flexiv_description. Licensed under the Apache License 2.0 (see LICENSE in the Flexiv_Enlight-L directory or the original notice for details). Note: Modified locally to update mesh resource paths.
  • Local Changes: Repackaged URDF into a flat Flexiv_Enlight-L/ directory; modified mesh resource paths to be relative to meshes/; mesh files themselves removed (see note above).
  • License Copy: Located at Flexiv_Enlight-L/LICENSE.md
• ANYmal D (ANYbotics) – Derived from the anymal_d_simple_description project. Licensed under the BSD 3-Clause License.
  • Local Changes: Repackaged URDF into a flat ANYbotics_ANYmal-D/ directory; modified mesh resource paths to be relative to meshes/; mesh files themselves removed (see note above).
  • License Copy: Located at ANYbotics_ANYmal-D/LICENSE.md
• Wuji Hand (Wuji Technology) – Derived from the wuji-description project. Licensed under the MIT License.
  • Local Changes: Repackaged URDF into a flat Wuji-Technology_Wuji-Hand/ directory; modified mesh resource paths to be relative to meshes/; mesh files themselves removed (see note above).
  • License Copy: Located at Wuji-Technology_Wuji-Hand/LICENSE.md
• Stretch 4 (Hello Robot) – Derived from the stretch4_urdf project. Licensed under the Clear BSD License.
  • Local Changes: Repackaged URDF into a flat Hello-Robot_Stretch4/ directory; modified mesh resource paths to be relative to meshes/; mesh files themselves removed (see note above).
  • License Copy: Located at Hello-Robot_Stretch4/LICENSE.md

Copies of the original licenses and any accompanying NOTICE files are preserved in the root directory or alongside the respective robot package folders.