Lappa

Lappa is a ROS2 package IDE for Windows-first (and Linux) workflows: open a package, edit with hot-reload, simulate offline, build fitted multi-link 3D robots, and optionally run a real ROS2 container — without installing a full ROS2 desktop on the host.

Layer	Role
Lappa IDE	Browser IDE — Monaco editor, explorer, teleop, 2D / WebGL 3D sim, package bundler, 3D model lab
Lappa Server	CLI + FastAPI — workspace, multi-distro ROS2, packager, mesh fit, native kinematics, Docker bridge
Desktop GUI	Native PySide6 app (`lappa-gui`) for sim, demos, models, packages, ROS2 status
Demos	Colcon-ready packages: diff-drive, omni, tricycle, ackermann, planar arm (+ meshes & URDF)
Docker runtime	Optional show mode: Humble / Iron / Jazzy / Kilted / Rolling

Product: mergeos-bounties/Lappa · MergeOS project prj_0352 · MIT

Highlights

Capability	What you get
Offline native sim	Diff-drive, omni, tricycle, ackermann, arm — pose, twist, synthetic lidar, wheel joint odometry
Full 3D	Auto-fit mesh AABB, multi-link robots (chassis + wheels + lidar), clean URDF, WebGL orbit viewer
No host ROS2 required	Demos run without installing ROS2 desktop on Windows/Linux host
Multi-distro targets	Humble · Iron · Jazzy · Kilted · Rolling — Dockerfiles rewrite for the selected distro
Package bundler	Zip one or many packages with `lappa_manifest.json` for colcon
Hot reload	File watch → sim session notified when you save in the IDE
Docker show mode	Optional container mount + runtime when Docker Desktop is available
Browser IDE	Activity bar, split panes, dark theme, teleop (WASD), 2D/3D toggle
Desktop GUI	PySide6 shell (`lappa-gui`) for offline demos without a browser

Screenshots

Captures from live product demos and the IDE.

IDE & Docker	Mobile base sims

IDE overview — explorer, Monaco, sim	Differential drive 2W

Docker show mode panel	Holonomic omni 3W

More robots	Trajectories & packages

Tricycle / steered base	Live trajectory · diff drive

Planar arm FK	Live trajectory · omni

	Demo package list (CLI/API)

3D WebGL: after lappa model build-robot <demo> (or IDE → Models → Build full 3D robot), open the sim panel and switch 2D → 3D for orbit view of chassis, wheels, and lidar.

Desktop GUI (Qt)

Modern PySide6 shell for simulation, demos, 3D models, package bundles, and ROS2/Docker — native desktop alongside the browser IDE.

cd packages\server
pip install -e ".[gui]"
lappa-gui
# or: lappa gui

Simulation + teleop canvas

Robot demos

3D mesh library & build-robot

Package bundles

ROS2 distro & Docker status

Quick start

From source (recommended for development)

Windows (PowerShell):

cd packages\server
python -m venv .venv
.\.venv\Scripts\activate
pip install -e ".[dev,api,gui]"

lappa version
lappa demo
lappa serve --port 8840
# or open browser automatically:
lappa desktop
# or native desktop:
lappa-gui

Linux / macOS:

cd packages/server
python -m venv .venv
source .venv/bin/activate
pip install -e ".[dev,api,gui]"
lappa demo
lappa serve --port 8840

Open http://127.0.0.1:8840 — demos load in the explorer; press ▶ Run Sim and teleop with WASD / QE (strafe).

Offline smoke demo

$ lappa demo
demos: 5  (ackermann_4w, diff_drive_2w, omni_3w, simple_arm, tricycle_3w)
3d_robot: diff_drive_2w · links=5 · scene_nodes=4
bundle + trajectory CSV · Lappa demo complete

CLI reference

Command	Description
`lappa version`	Package version
`lappa demo`	Offline smoke: all engines + 3D robot build + bundle + trajectory
`lappa gui` / `lappa-gui`	Qt desktop app (needs `.[gui]`)
`lappa serve [--host] [--port] [--open]`	FastAPI + static IDE
`lappa desktop`	Serve and open the system browser
`lappa demos list`	List robot demos
`lappa workspace open <path\|demo>`	Set active package
`lappa sim start --demo <id>`	Start native sim session
`lappa sim status`	Session status
`lappa ros2 list \| set \| get`	Target ROS2 distro
`lappa package list \| bundle \| bundles`	Colcon-ready zip packs
`lappa model presets \| create \| list`	Procedural OBJ library
`lappa model fit`	Auto-scale mesh AABB to a target box
`lappa model attach`	Fit-attach mesh onto a package link / URDF
`lappa model build-robot`	Full multi-link robot (chassis + wheels + lidar)
`lappa model scene`	Print `scene3d` JSON for a package
`lappa docker status`	Docker availability / distro

lappa demos list
lappa workspace open demos/diff_drive_2w
lappa sim start --demo diff_drive_2w
lappa ros2 set jazzy
lappa package bundle -p diff_drive_2w -p omni_3w --distro humble
lappa model build-robot diff_drive_2w
lappa model scene diff_drive_2w

Robot demos

Each entry under packages/demos/ is a ROS2-style package (package.xml, launch/, urdf/, Python nodes, meshes/).

Id	Kinematics	3D layout (`build-robot`)	Notes
`diff_drive_2w`	Differential drive	Chassis + L/R wheels + lidar	Classic mobile base
`omni_3w`	Holonomic 3-wheel	Chassis + 3 wheels @ 120° + lidar	Strafe + rotate
`tricycle_3w`	Tricycle	Chassis + steer + rear pair + lidar	Steering geometry
`ackermann_4w`	Ackermann car-like	Chassis + 4 wheels + lidar	Wheelbase + steer
`simple_arm`	Planar 2-DOF	Base + link1 + link2	Joint angles / FK tip

Sim state includes x, y, theta, twist, synthetic lidar, and joints (wheel spin / arm angles) for the 3D viewer.

3D stack

Lappa treats 3D as a first-class workflow: generate → fit → assemble → view → bundle.

Mesh library & auto-fit

Preset	Use
`box`	Generic body
`cylinder`	Pillar / vertical body
`sphere`	Ball / joint hint
`wheel`	Thin cylinder (Y-axis spin)
`chassis`	Mobile base plate
`arm_link`	Elongated arm segment
`lidar_dome`	Hemisphere sensor

lappa model create chassis -n my_chassis
lappa model create wheel -n my_wheel
lappa model fit my_chassis --sx 0.42 --sy 0.30 --sz 0.10
lappa model attach diff_drive_2w my_chassis --auto-fit --link base_link

Fit semantics

Parse OBJ vertices → axis-aligned bounding box (AABB).
Compute per-axis (or uniform) scale so size matches the target.
Center the mesh at the origin so URDF xyz is a true link offset.
Write fitted OBJ into package/meshes/ and update urdf/robot.urdf via visual upsert.

Build a full aligned robot

lappa model build-robot diff_drive_2w
lappa model build-robot omni_3w
lappa model build-robot ackermann_4w

Produces:

base_footprint
  └── base_link          (chassis mesh)
        ├── wheel_*      (continuous joints, kinematic xyz / yaw)
        └── lidar_link   (fixed joint)   # mobile bases

Wheel centers sit on the ground plane relative to footprint height.
Attachments registry: meshes/attachments.json.
Valid multi-link URDF (no orphan duplicate links).

IDE 3D viewer

Open a demo package.
Models → Build full 3D robot (or use CLI).
Sim panel → toggle 3D.
Orbit: drag to rotate · mouse wheel to zoom.
Teleop (WASD) — wheels animate from joint odometry.

scene3d contract

GET /api/packages/{name}/scene3d returns a viewer-ready graph (ROS REP-103: x forward, y left, z up; WebGL maps ROS → Three.js Y-up automatically).

{
  "package": "diff_drive_2w",
  "frame": "base_footprint",
  "up": [0, 0, 1],
  "forward": [1, 0, 0],
  "nodes": [
    {
      "link": "base_link",
      "mesh_url": "/api/packages/diff_drive_2w/mesh/diff_drive_2w_chassis.obj",
      "xyz": [0, 0, 0],
      "rpy": [0, 0, 0],
      "scale": [1, 1, 1],
      "role": "chassis",
      "bounds": { "size": [0.42, 0.3, 0.1], "center": [0, 0, 0] }
    }
  ]
}

ROS2 versions

lappa ros2 list
lappa ros2 set jazzy
lappa ros2 get

Id	Image	Notes
`humble`	`ros:humble-ros-base`	Default LTS (Ubuntu 22.04)
`iron`	`ros:iron-ros-base`	Legacy
`jazzy`	`ros:jazzy-ros-base`	LTS Ubuntu 24.04
`kilted`	`ros:kilted-ros-base`	Interim
`rolling`	`ros:rolling-ros-base`	Bleeding edge

In the IDE: title bar → ROS2 dropdown. Starting Docker regenerates packages/docker/Dockerfile for the selected distro.

Package bundles

lappa package list
lappa package bundle -p diff_drive_2w -p omni_3w --distro humble
lappa package bundles

Or IDE → Package → select packages → Create bundle zip.

Artifacts live under the server workspace (e.g. .workspaces/bundles/).

src/<pkg>/...          # package sources including meshes/ + urdf/
lappa_manifest.json    # distro, packages, Lappa version
README_BUNDLE.md

HTTP API

Base URL when serving: http://127.0.0.1:8840

Method	Path	Purpose
`GET`	`/health`	Health + version + demos
`GET`	`/api/demos`	Demo package list
`POST`	`/api/workspace/open`	Open demo / path
`GET`	`/api/files?path=`	Read package file
`PUT`	`/api/files`	Write file (hot-reload)
`POST`	`/api/sim/start`	Start native sim
`POST`	`/api/sim/cmd`	Publish twist
`GET`	`/api/sim/state`	Pose / joints / lidar
`GET`	`/api/sim/trajectory.csv`	Trajectory export
`GET`	`/api/ros2/versions`	Distro list + selected
`POST`	`/api/packages/bundle`	Create zip bundle
`GET`	`/api/models/presets`	Mesh presets
`POST`	`/api/models`	Create procedural mesh
`POST`	`/api/models/fit`	Auto-fit library mesh
`POST`	`/api/models/attach`	Fit-attach to package
`POST`	`/api/models/build-robot`	Full aligned robot
`GET`	`/api/packages/{pkg}/scene3d`	3D scene graph
`GET`	`/api/packages/{pkg}/mesh/{file}`	Raw OBJ for WebGL
`GET`	`/api/docker/status`	Docker probe

Docker (optional)

Requires Docker Desktop (or a Docker engine on Linux).

# From repository root
docker compose -f packages/docker/docker-compose.yml up --build
# or IDE → Docker → Start runtime

Without Docker, the native kinematics sim still runs fully offline. Docker is for real ros2 launch / distro fidelity.

Download binaries

GitHub Releases ship standalone builds (no Python install):

File	Platform
`lappa-windows-x64.exe`	Windows 10/11 x64
`lappa-linux-x64`	Linux x64

.\lappa-windows-x64.exe          # opens http://127.0.0.1:8840
.\lappa-windows-x64.exe demo

chmod +x lappa-linux-x64
./lappa-linux-x64
./lappa-linux-x64 ros2 list

Local release build: see docs/RELEASE.md.

pwsh scripts\build_release.ps1
# → dist\release\lappa-windows-x64.exe

Tag v* on GitHub → Actions builds both OS assets.

Diagrams

System architecture and workflow — full width. Open the HTML files for dark/light theme and export (PNG/SVG).

Architecture

Open interactive diagram

Workflow

Open interactive diagram

Generated with archify.

┌─────────────────────────────────────────────────────────────┐
│  Browser IDE  (packages/ide)  ·  Qt GUI (lappa-gui)         │
│  Monaco · Explorer · Teleop · 2D canvas · Three.js 3D       │
└───────────────────────────┬─────────────────────────────────┘
                            │ HTTP /api/*  or  in-process
┌───────────────────────────▼─────────────────────────────────┐
│  Lappa Server  (packages/server)                            │
│  · workspace / files / hot-reload                           │
│  · native kinematics engines                                │
│  · models3d: fit · attach · build-robot · scene3d           │
│  · packager + ros2 version store                            │
│  · docker_bridge                                            │
└───────────┬─────────────────────────────┬───────────────────┘
            │                             │
   packages/demos/*              packages/docker (optional)
   (URDF + meshes + launch)      ros:humble|jazzy|…

Repository layout

Lappa/
├── packages/
│   ├── server/          # Python CLI + FastAPI (lappa) + gui/
│   │   ├── src/lappa/   # api, models3d, sim, packager, docker_bridge, gui
│   │   └── tests/
│   ├── ide/             # Static IDE (index.html, ide.js, ide.css)
│   ├── demos/           # ROS2-style robot packages + meshes/URDF
│   └── docker/          # Dockerfile, compose, entrypoint
├── docs/
│   ├── screenshots/     # README gallery
│   ├── diagrams/        # Architecture + workflow
│   ├── BOUNTY.md
│   ├── RELEASE.md
│   └── ROADMAP.md
├── scripts/             # release builds, bounties, screenshots
└── README.md

Development

cd packages\server
pip install -e ".[dev,api,gui]"
pytest -q
ruff check src tests
lappa demo

Area	Path
3D fit / URDF / scene	`src/lappa/models3d.py`
Kinematics engines	`src/lappa/sim/engines.py`
HTTP API	`src/lappa/api.py`
Qt desktop GUI	`src/lappa/gui/`
IDE client	`packages/ide/assets/ide.js`
Demo packages	`packages/demos/*`

Roadmap

Version	Status	Focus
v0.1	Shipped	IDE shell, native sim, demos, Docker scaffold
v0.2	Shipped	Multi-distro ROS2, packager, procedural meshes, trajectory CSV
v0.3	Shipped	Mesh auto-fit, multi-link robots, scene3d, WebGL viewer
v0.4	Shipped	Qt desktop GUI, sim polish, full 3D fit path
Later	—	Live Docker `ros2 launch`, topic graph, Gazebo/Ignition, Foxglove

Details: docs/ROADMAP.md.

MergeOS bounties

Contribute sim features, IDE UX, 3D tooling, or docs — earn MRG after merge.

Star this repo and mergeos
Claim a bounty issue on Lappa
Claim on MergeOS Claim Token #1
Open a PR to master with tests / evidence
Maintainer merges → ledger credit 25 / 50 / 100 / 200 MRG

Policy: docs/BOUNTY.md.

Tiếng Việt (tóm tắt)

Lappa là IDE gói ROS2: sửa code, hot-reload, mô phỏng offline (không cần cài ROS2 trên máy), khớp mesh 3D, build robot nhiều link, xem WebGL 3D, đóng gói zip theo distro, Docker tùy chọn, GUI Qt (lappa-gui).

pip install -e "packages/server.[dev,api,gui]"
lappa demo
lappa model build-robot diff_drive_2w
lappa serve --port 8840
lappa-gui

IDE: http://127.0.0.1:8840 → Models → Build full 3D robot → Sim → 3D.

Name		Name	Last commit message	Last commit date
Latest commit History 26 Commits
.github/workflows		.github/workflows
docs		docs
lappa/server/api		lappa/server/api
packages		packages
scripts		scripts
tests		tests
.gitignore		.gitignore
LICENSE		LICENSE
README.md		README.md

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Lappa

Table of contents

Highlights

Screenshots

Desktop GUI (Qt)

Quick start

From source (recommended for development)

Offline smoke demo

CLI reference

Robot demos

3D stack

Mesh library & auto-fit

Build a full aligned robot

IDE 3D viewer

scene3d contract

ROS2 versions

Package bundles

HTTP API

Docker (optional)

Download binaries

Diagrams

Architecture

Workflow

Repository layout

Development

Roadmap

MergeOS bounties

Tiếng Việt (tóm tắt)

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About

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Repository files navigation

Lappa

Table of contents

Highlights

Screenshots

Desktop GUI (Qt)

Quick start

From source (recommended for development)

Offline smoke demo

CLI reference

Robot demos

3D stack

Mesh library & auto-fit

Build a full aligned robot

IDE 3D viewer

scene3d contract

ROS2 versions

Package bundles

HTTP API

Docker (optional)

Download binaries

Diagrams

Architecture

Workflow

Repository layout

Development

Roadmap

MergeOS bounties

Tiếng Việt (tóm tắt)

License

About

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