Design stunning 2D & 3D particle effects visually — and play them in GDevelop.
A standalone desktop editor with real-time GPU preview, paired with the Advanced Particle Emitter extension for GDevelop.
⬇️ Download · 🎮 itch.io · ✨ Features · 🚀 Quick Start · 🎨 Blend Modes · 📚 Docs · 🛣️ Roadmap
Lempo Particle Editor is a two-part toolkit:
| Part | What it is |
|---|---|
| Lempo Particle Editor | A Dear PyGui desktop app (LempoParticleEditor.exe) for designing effects with a live viewport, then exporting them as JSON. |
| Advanced Particle Emitter | A GDevelop extension (AdvancedParticleEmitter.json) that renders those effects in-game: 2D via PixiJS and 3D via Three.js. |
Both parts share a single source of truth for particle behavior, shapes, and the export format (see Shared Contracts), so an effect looks the same in the editor, the browser preview, and your game.
Works in any GDevelop project — design the effect in the editor, play it in-game with the Advanced Particle Emitter extension.
 3D viewport |
 2D viewport |
 3D browser fast preview |
 2D browser fast preview |
 Emitter panel |
 Per-state colors (3D) |
 Trails & Ribbons (2D) |
 Trails & Ribbons (3D) |
More screenshots
 States panel (2D) |
 Custom shape |
 3D shapes (1) |
 3D shapes (2) |
 2D shapes |
|
- 12 particle shapes — circle, square, triangle, star, diamond, line, custom, sphere, cube, pyramid, torus, billboard — shared by the 2D and 3D renderers.
- Custom 3D models & images — upload
.glb/.gltf/.obj(or images for 2D). Models render as themselves in the viewport, the browser preview, and in-game. Rigged/skinned GLBs are baked to their rest pose automatically. - Per-state colors — birth / mid / death each keep their own color. White means natural materials; any other color tints over the base.
- Gradual shape morph — birth-to-death shapes cross-fade inside the
(0.25, 0.75)window instead of snapping (desktop viewport + browser preview; game runtime keeps the classic swap for meshes). - Ready-made templates — Explosion, Fire, Rain, Snow (2D + 3D variants), with 100-step undo/redo.
- Force fields (v1.1) — age-phased turbulence, Y-axis vortex, linear-falloff attractor, and a bounce/friction collision plane. All off by default (legacy motion stays bit-identical).
- Deterministic seed — a nonzero
seedreplays the identical effect everywhere: editor (Python + C++), browser preview, and GDevelop runtime.0keeps legacy unseeded behavior. - Blend modes — Normal, Additive, Subtractive, Multiply, Screen, Lighten, Overlay, selectable per emitter (see Blend Modes).
- Trails & Ribbons — a dedicated mode (key
4for 2D, key5for 3D in the startup dialog) with a Unity-style inspector, width/gradient curve editors,time/distanceemission, and a browser of 27 ready-made templates (combat, magic, movement, nature, stylized) with search, favorites, and your own saved presets. 👉 Full details: docs/trails.md
The Dear PyGui sidebar exposes blend, seed, and force-field widgets. The Tk fallback preserves those values on round-trip but has no widgets for them.
- InstancedMesh batching (3D primitives) — ~580 draw calls collapse into ~12 buckets, verified pixel-identical per particle (matrix, color, alpha), including morph flips and all blend modes.
- Lazy buckets & pooled runtime — empty buckets cost zero draw calls, and shape-aware mesh/material pooling keeps steady state free of per-frame allocations. Automatic fallback to the classic path if instancing is unavailable.
- Dual simulation core — a Python reference plus an optional compiled C++ core for faster live preview, checked for numerical parity (99/99 cases) against Python.
- Adaptive viewport — crisp vector drawlist for small particle counts; above ~900 particles the particle layer renders offscreen and uploads as a texture while guides/gizmo stay vector.
- In-editor GPU preview — a minimal offscreen OpenGL 3.3 renderer built on raw
ctypes(no PyOpenGL or numpy needed). - Browser fast preview — a self-contained
live_effect.html(≈1.1 MB, zero network fetches) rendering the same effect live in Three.js (3D) / PixiJS (2D), with 500 ms live-sync. Trail mode renders ribbons in the preview too and hides the particle dots, exactly like the editor viewport. - In-game trails (extension v0.2.0) — exported trail effects render as ribbons inside GDevelop as well (2D quad strips, 3D billboard strips, pooled and blend-aware), with
hideParticlehonored. No new objects: the existing emitters grow trail support, and trail-less effects render bit-identical to before. - OS-native file dialogs — Save / Export / Open use the OS file picker, because Dear PyGui's built-in dialogs return empty results here.
Download LempoParticleEditor.exe from the Releases page (or from itch.io) and run it. No Python installation required. The window title shows v0.2.0; it pairs with extension v0.2.0 and export format v1.1 (v1.0 files migrate automatically).
Requirements: Windows 10/11 (64-bit) · GPU with OpenGL 3.3 support
Run from source / rebuild
pip install dearpygui
python editor/studio_imgui.pyTk fallback (shared logic layer, no blend/seed/field widgets — values are preserved):
python editor/particle_studio.pyRebuild the packaged app (compile check → C++ core build if stale → PyInstaller → smoke test → Windows shortcut):
python tools/rebuild_app.pyThis produces dist/LempoParticleEditor.exe plus the Lempo Particle Editor desktop shortcut (both carry the Lempo icon).
Binaries (
dist/,*.exe,*.pyd,node_modules/) are never committed. They are rebuilt locally and shipped through GitHub Releases.
- Design your effect in Lempo Particle Editor and export it as a
.jsonfile. - Import
AdvancedParticleEmitter.jsoninto your GDevelop project as an extension. - Add the emitter object to your scene and set its ParticleJSON resource to the exported file. If the effect uses a custom model, also set the Models GLB resource to your
.glb. - Run the preview and enjoy your effect in-game.
Exact action/condition names depend on the extension version — see the extension's in-editor descriptions.
Set per emitter from the sidebar dropdown. At object level, BlendingMode: 'JSON' uses each emitter's own mode; any explicit value forces all emitters.
| Mode | 2D (PixiJS) | 3D (Three.js) | Desktop GL preview | Browser preview |
|---|---|---|---|---|
| Normal | normal | normal | SRC_ALPHA, ONE_MINUS_SRC_ALPHA |
normal |
| Additive | add | additive | SRC_ALPHA, ONE |
add |
| Subtractive | erase ¹ | subtractive | reverse-subtract | erase ¹ |
| Multiply | multiply | multiply | DST_COLOR, ONE_MINUS_SRC_ALPHA |
multiply |
| Screen | screen | custom (add + ONE, ONE_MINUS_SRC_COLOR) |
ONE, ONE_MINUS_SRC_COLOR |
screen |
| Lighten | → Normal ² | custom max-equation | max | → Normal ² |
| Overlay | overlay | → Normal ³ | → Normal ³ | overlay |
¹ Pixi core has no subtract · ² Pixi core has no lighten · ³ No fixed-function overlay
Unsupported combinations fall back to Normal with a single console.warn — never per frame, never throwing. Extension versions before 0.1.2 don't know Screen / Lighten / Overlay and render them as Normal.
Everything that must stay identical across Python, C++, the browser preview, and the GDevelop extension lives in one place: contracts/contracts.json — particle record layout, SHAPE_ORDER, easings, blend modes, export schema, and morph window.
Edit the JSON, run tools/generate_contracts.py, never the generated outputs. CI fails on stale files or drifted consumers.
Export format v1.1 is validated on save and load, and migrate_effect() heals old files automatically (v1.0 → v1.1, missing blend mode / seed, camelCase easings).
👉 Full details (generated bindings, consumers, particle record layout): docs/contracts.md
| Folder | Contents |
|---|---|
editor/ |
Desktop app — Dear PyGui UI (studio_imgui.py), Tk fallback and shared logic layer (particle_studio.py) |
core/ |
C++ simulation core (particle_core.cpp) + parity and behavior tests |
render/ |
In-editor OpenGL renderer and render tests |
preview/ |
Browser fast preview (Three.js / PixiJS) and its tests |
carrots-runtime/ |
TypeScript runtime copy used by the GDevelop extension |
contracts/ |
Shared contracts (contracts.json) and generated bindings (gen/) |
assets/ |
App icon and bundled presets (presets/trails/) |
presets/ |
Effect presets |
bench/ |
Benchmarks |
packaging/ |
Build / packaging files for the Windows app |
tests/ |
Python test suite |
tools/ |
Build, contract-generation, and CI helper scripts |
docs/ |
Documentation and screenshots |
CI runs the parity, behavior, and contract checks on every push (.github/workflows/ci.yml). Highlights: Python ↔ C++ parity (99/99), seed replay, force fields, blend modes, trails, and the shipped GDevelop runtime tested headlessly.
👉 Full test matrix: docs/testing.md
| Doc | What's inside |
|---|---|
| docs/trails.md | Trails & Ribbons — modes, emit types, template format, adding your own template, C++ API |
| docs/contracts.md | Shared contracts, generated bindings, export format, particle record layout |
| docs/testing.md | Full test matrix |
| APP_STRUCTURE.md | App architecture notes |
| PROGRESS.md | Development progress log |
Done
- Ready-made effect templates (Explosion, Fire, Rain, Snow)
- CI for parity and behavior tests
- Screenshots and a step-by-step GDevelop guide
- InstancedMesh batching, lazy buckets, sampling diet (v0.1.2)
- Screen / Lighten / Overlay blend modes (v0.1.2)
- Deterministic seed + force fields (v0.1.2)
- Trails & Ribbons renderer (79-key TRAIL_SCHEMA, 27 templates, Godot-style distance emission, C++ registry + DPG browser) (v0.2.0)
- Template browser with search, favorites, and user presets + world-space 2D zoom
- Over-life Bézier curves and gradient editor
Planned
- Flipbook animation, UV scroll, soft particles
- Effect node tree with parent/child emitters and sub-emitters
- Timeline with scrubbing and a preset gallery
- Golden-image tests (editor render vs browser preview)
Mostafa Fathy (EG dev) — independent developer (@Boy1developer).
🎬 YouTube: youtube.com/@EG_dev
| Library | License | Used for |
|---|---|---|
| Dear PyGui | MIT | Desktop editor UI |
| Three.js | MIT | 3D rendering (browser preview + GDevelop extension) |
| PixiJS | MIT | 2D rendering (browser preview + GDevelop extension) |
Released under the MIT License.
Made by Mostafa Fathy (EG dev) · 🎬 YouTube · If this helps your game, consider giving it a ⭐