urdx

Create URDF robot definitions using JSX

This is essentially a templating engine for rendering URDF files using javascript. This allows:

Programmatic shape definitions.

Mass and inertia tensor can be automatically calculated for standard shapes: Box, Cylinder, Sphere. For example:

<Cylinder name="base" length={0.1} radius={0.1} />

becomes:

<link name="base_link">
  <visual>
    <geometry>
      <cylinder length="0.1" radius="0.1"/>
    </geometry>
  </visual>
  <collision>
    <geometry>
      <cylinder length="0.1" radius="0.1"/>
    </geometry>
  </collision>
  <inertial>
    <mass value="3.141592654"/>
    <inertia ixx="0.010471976" ixy="0" ixz="0" iyy="0.010471976" iyz="0" izz="0.015707963"/>
  </inertial>
</link>

Hierarchies and inheritance.

Define a joint between a parent and child just by making the child a syntactic child of the parent. Also allows children to inherit properties e.g. material of their parent. For example:

<Cylinder name="base" length={0.1} radius={0.1} material={{name: 'blue'}}>
  <Box name="child" dx={0.1} dy={0.1} dz={0.1} />
</Cylinder>

becomes:

<link name="base_link">
  <visual>
    <geometry>
      <cylinder length="0.1" radius="0.1"/>
    </geometry>
    <material name="blue"/>
  </visual>
  ...
</link>
<link name="child_link">
  <visual>
    <geometry>
      <box size="0.1 0.1 0.1"/>
    </geometry>
    <material name="blue"/>
  </visual>
  ...
</link>
<joint name="child_joint" type="fixed">
  <parent link="base_link"/>
  <child link="child_link"/>
</joint>

Mixed XML.

Valid XML is valid JSX. So you can write:

<Cylinder name="base" length={0.1} radius={0.1} />
<link name="child_link">
  <visual>
    <geometry>
      <box size="0.1 0.1 0.1"/>
    </geometry>
  </visual>
</link>
<joint name="child_joint" type="fixed">
  <parent link="base_link"/>
  <child link="child_link"/>
</joint>

Get started

Create a new folder and add this as package.json:

{
  "name": "my-super-robot",
  "version": "1.0.0",
  "description": "My Super Robot Definition",
  "scripts": {
    "build": "babel urdx -d .urdx",
    "postbuild": "node .urdx/index.js"
  },
  "devDependencies": {
    "@babel/cli": "^7.1.0",
    "@babel/core": "^7.1.0",
    "@babel/plugin-transform-react-jsx": "^7.1.0",
    "@babel/preset-env": "^7.1.0"
  },
  "dependencies": {
    "urdx": "latest"
  },
  "babel": {
    "plugins": [["@babel/plugin-transform-react-jsx", {"pragma": "urdx.createElement", "throwIfNamespace": false}]],
    "presets": ["@babel/env"]
  }
}

Then run npm i. Create directories called urdx and urdf, and then add urdx/index.js:

import urdx, { Cylinder } from 'urdx';
 
const robot = (
  <Cylinder name="base" length={0.1} radius={0.1} />
)
 
const files = [
  {
    filename: 'myfirst.urdf',
    args: {
      name: 'myfirst'
    },
    robot,
  },
];
 
urdx.writeOutput(files);

Then run npm run build. Voilà! Your robot will show up in the urdf folder.

Look in the folder of this project called urdx to see some more detailed examples!