urdf_parser

Description:

urdf parser

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 at the time iOS, Android, macOS and Windows.
Basic Usage #
Requires working three_dart project.
Inside of your initPage() function load your dae/stl files or urdf model.
void initPage() async {
scene = three.Scene();
// ...

// --- STL ---
three.Object3D stlObject = await STLLoader(null).loadAsync("path to stl file");
scene.add(stlObject);

// --- DAE ---
List<three.Object3D> daeObjects = await DAELoader.loadFromPath('path to dae file', []);
for (three.Object3D object in daeObjects) {
scene.add(object);
}

// --- URDF ---
// 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());
}
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Move joints #
In the urdf file defined joints can then be moved via trySetAngle().
robot.trySetAngle("angleName", amount);
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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)!,
);

// ...
}
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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/ ascii stl files, dae files and basic urdf color nodes
Supports parsing of lines data of dae files

Colors Formats #
Besides the obvious defined material definition of dae files, also stl files can containt color information. But there is unfortunately no official standard.
This library supports the following stl color formats:
Ascii STL Color Format #
solid object1
facet normal 0.0 0.0 0.0
outer loop
vertex 1.0 0.0 0.0
vertex 0.0 1.0 0.0
vertex 0.0 0.0 1.0
endloop
endfacet
endsolid object1=RGB(0,0,255)

solid object2
facet normal 0.0 0.0 0.0
outer loop
vertex -1.0 0.0 0.0
vertex 0.0 -1.0 0.0
vertex 0.0 0.0 -1.0
endloop
endfacet
endsolid object2=RGB(255,0,0)
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If color information is provided then each solid must contain it. Otherwise a default white materials is used for each solid.
Binary STL Color Format #
Supports the "Magics" color format from https://en.wikipedia.org/wiki/STL_(file_format)#Binary.

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 facing up, a transformation is performed from the z-axis upwards facing stl/dae formats.

License

For personal and professional use. You cannot resell or redistribute these repositories in their original state.

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