Motus.OMPL.NET 0.13.0

Motus.NET

.NET 8 host-agnostic motion-planning core: models, FK/IK, collision, sampling/Cartesian planners, retiming, and export.

No UI, no vendor runtime, no live robot I/O. Algorithm catalog: docs/METHODS.md · citations: docs/REFERENCES.bib.

Bundled presets (UR family) and URDF / xacro loaders; analytic IK for Universal Robots, numerical IK for generic chains. Parallel Stewart (Family=stewart, leg lengths in meters) and legged gait preview (Family=legged, radians) are first-class siblings of serial tip chains.

Licensed under MIT.

Contents

• Packages
• Quick start
• Planners
• Algorithms and references
• Context: attach, groups, SRDF
• Units and export
• Build and test
• Releases
• Safety
• Attribution

Packages

dotnet add package Motus.Core
dotnet add package Motus.Geometry
dotnet add package Motus.OMPL.NET
dotnet add package Motus.Presets

Rhino / desktop: managed planning and C# mesh collision are the default — no Linux .so required. See docs/rhino-host.md. Stub/NuGet builds often expose only RrtConnect in the planner registry; extra OMPL IDs need a full native build. Check MotusCapabilities.Describe().

Quick start

var robot = PresetLoader.LoadRobotModelByName("UR10e");
var start = HomePoseResolver.HomeOrZeros(robot);
var goal = new JointState(/* radians */);

var scene = new CollisionScene(new[] {
    CollisionObject.Sphere("obstacle", Frame.Identity, 0.1)
});
var checker = CollisionCheckerFactory.Create(robot);
var opts = new PlanningOptions {
    CollisionScene = scene,
    CollisionChecker = checker
};

var result = SamplingPlanner.Create(checker, new SamplingPlannerOptions {
    PlannerId = SamplingPlannerId.RrtConnect,
    MaxIterations = 4000
}).Plan(new PlanningRequest(robot, start, goal, opts));

if (result.Success)
    File.WriteAllText("plan.json", TrajectoryExport.ToJson(result.Trajectory!));

URDF:

var robot = UrdfRobotLoader.Load("robot.urdf", new UrdfLoadOptions {
    BaseLink = "base_link",
    TipLink = "tool0"
});
var fk = KinematicsResolver.CreateFkSolver(robot.Preset, robot.Chain);

Planners

Prefer SamplingPlanner + CollisionCheckerFactory.Create (or GetOrCreate for session reuse) over the obsolete RrtConnectPlanner wrapper.

// Motion program
var planner = new IndustrialMotionPlanner(robot.Preset);
var result = planner.Plan(new MotionProgramRequest(robot, start, new MotionSegment[] {
    new PtpSegment(ptpGoal, blendRadiusMeters: 0.004),
    new LinSegment(linGoal, stepMeters: 0.005),
    new CircSegment(via, circGoal, arcSamples: 12)
}));

Algorithms and references

Canonical detail (API, units, failure codes): docs/METHODS.md. BibTeX: docs/REFERENCES.bib.

<details> <summary><strong>Method catalog</strong> — area, behavior, citations (click to expand)</summary>

</details>

Context: attach, groups, SRDF

var ctx = PlanningContext.Create(robot, scene)
    .Attach("workpiece", workpieceBox, tcpLocalFrame)
    .ForGroup(SrdfLoader.LoadGroups("robot.srdf")[0]);

var checker = CollisionCheckerFactory.Create(robot, attached: ctx.Attached);
var result = SamplingPlanner.Create(checker).Plan(
    new PlanningRequest(robot, start, goal, ctx.ToPlanningOptions()));

Non-group joints stay locked at the start configuration.

Units & export

Internal units: radians, seconds, meters (Motus.Core.Units for °↔rad). Stewart configurations are meters (leg stroke); legged joints are radians.

TrajectoryExport.ToJson emits the PlanBundle contract for Grasshopper and control adapters:

• contractVersion / exportVersion — schema compatibility
• units, frameConvention — semantics
• diagnostics — machine-readable planner messages
• provenance — optional plannerId, seed, settings hash

Additive optional fields are safe; removing/renaming fields requires a major contractVersion bump.

Build & test

Requires .NET 9+ SDK to open the .slnx; libraries target net8.0.

dotnet build Motus.NET.slnx
dotnet test Motus.NET.slnx

Optional native library:

cmake -S native -B native/build -DMOTUS_USE_OMPL=ON -DMOTUS_USE_FCL=ON
cmake --build native/build
# Linux: export LD_LIBRARY_PATH=native/build

Benchmarks: benchmarks/Motus.Benchmarks (BenchmarkDotNet).

Releases

Tag vX.Y.Z → release workflow builds, tests, packs, publishes to nuget.org, and creates a GitHub Release.

Changelog: CHANGELOG.md. Current pin for Grasshopper: 0.13.0.

Safety

Motus does not command physical robots. Presets and URDF imports are planning defaults — verify limits and calibration before hardware use. See docs/safety.md.

This library and bundled presets were developed with AI assistance; values are approximate and must be checked against manufacturer data.

Attribution

• Managed RRT-Connect implements Kuffner & LaValle (ICRA 2000). Native path uses OMPL (BSD-3-Clause) when built.
• Robot presets are approximate public-datasheet values for planning/visualization only.