urdf_parser 0.0.2

A urdf parser extension for three_dart that also includes a dae/stl loader.

Flutter URDF-Parser

This library is majorly an extended dart port of https://github.com/gkjohnson/urdf-loaders for the dart three_js port of https://github.com/wasabia/three_dart.

It includes a STL + DAE loader, URDF parser and quaternion + vector3 extension class.

Works with all plattforms that three_dart currently supports. Which are currently Web, iOS, Android, macOS and Windows.

Basic Usage

Requires working three_dart project.

Inside of your initPage() function load your urdf model.

void initPage() async {
    scene = three.Scene();
    // ...

    // parse the urdf file to a URDFRobot object
    URDFRobot? robot = await URDFLoader.parse(
        "path to urdf file",
        "path to urdf content folder where stl/dae files are located",
    );

    // create a three_dart recursive object and add it to the scene
    scene.add(robot.getObject());
}

Move joints

In the urdf file defined joints can then be moved via trySetAngle().

robot.trySetAngle("angleName", amount);

Basic example to animate all available joints sequentially

void render() {
    // ...

    double time = DateTime.now().millisecondsSinceEpoch / 6e4;

    List<MapEntry<String, URDFJoint>> joints = (robot!.joints.entries.where(
        (entry) => entry.value.type != "fixed")).toList();

    // robot joint test animation
    double periodicValueSmall = sin((time * joints.length) % 1 * 2 * pi) / 2 + 0.5;
    int s = (time * joints.length).floor() % joints.length;

    // set last angle rotation to 0.5
    int lastS = (s - 1 + joints.length) % joints.length;
    robot!.trySetAngle(
        joints[lastS].key, 
        lerpDouble(joints[lastS].value.lower, joints[lastS].value.upper, 0.5)!,
    );

    robot!.trySetAngle(
        joints[s].key, 
        lerpDouble(joints[s].value.lower, joints[s].value.upper, periodicValueSmall)!,
        );

    // ...
}

Supported Joint Types

• fixed
• continuous
• revolute
• prismatic
• mimic

Supported 3D File Types

• .stl/ .STL (both binary and ascii variants)
• .dae

Additional Features

• Supports color extraction of binary stl files, dae files and basic urdf color nodes

NOTE

As this library is a C# port of https://github.com/gkjohnson/urdf-loaders which was written for Unity. The library contains its own implementation of a hierarchy system using the HierarchyNode class with local/ global transformations. The getObject() function on the URDFRobot class then formats the custom hierarchy implementation to a three_dart group with set children.

And as three_dart uses a coordinate system where the y-axis is typically up, a transformation is performed for each stl/dae mesh where the z-axis is facing upwards.