# `k`: Kinematics library for rust-lang [![Build Status](https://travis-ci.org/OTL/k.svg?branch=master)](https://travis-ci.org/OTL/k) [![crates.io](https://img.shields.io/crates/v/k.svg)](https://crates.io/crates/k)
`k` has below functionalities.
1. Forward kinematics
1. Inverse kinematics
1. URDF Loader
`k` uses [nalgebra](http://nalgebra.org) as math library.
See [Document](http://docs.rs/k) and examples/ for more details.
API is unstable.
## Requirements to build examples
```bash
sudo apt install g++ cmake xorg-dev libglu1-mesa-dev
```
## IK example with GUI
```bash
cargo run --release --example interactive_ik
```
![ik_sample](img/screenshot.png)
Push below keys to move the end of the manipulator.
- `f`: forward
- `b`: backward
- `p`: up
- `n`: down
- `l`: left
- `r`: right
- `z`: reset the manipulator state.
## Create link tree from urdf and solve IK
```rust
use k::prelude::*;
fn main() {
// Load urdf file
let chain = k::Chain::<f32>::from_urdf_file("urdf/sample.urdf").unwrap();
println!("chain: {}", chain);
// Set initial joint angles
let angles = vec![0.2, 0.2, 0.0, -1.0, 0.0, 0.0, 0.2, 0.2, 0.0, -1.0, 0.0, 0.0];
chain.set_joint_positions(&angles).unwrap();
println!("initial angles={:?}", chain.joint_positions());
let target_link = chain.find("l_wrist_pitch").unwrap();
// Get the transform of the end of the manipulator (forward kinematics)
chain.update_transforms();
let mut target = target_link.world_transform().unwrap();
println!("initial target pos = {}", target.translation);
println!("move z: +0.1");
target.translation.vector.z += 0.1;
// Create IK solver with default settings
let solver = k::JacobianIKSolver::default();
// Create a set of joints from end joint
let arm = k::SerialChain::from_end(target_link);
// solve and move the manipulator angles
solver.solve(&arm, &target).unwrap();
println!("solved angles={:?}", chain.joint_positions());
chain.update_transforms();
let solved_pose = target_link.world_transform().unwrap();
println!("solved target pos = {}", solved_pose.translation);
}
```
## Structure of API
Top level interface is `Chain` struct. It contains `Node`s and they have the relations between nodes (parent/children).
Actual data (joint angle(position), transform between nodes) is stored in `Joint` object inside nodes.
![ik_sample](img/chain.png)
You can get local/world transform of nodes. See below figure to understand what is the node's `local_transfrom()` and `world_transfrom()`.
![ik_sample](img/transform.png)