Codebase walkthrough

A package-by-package guide to the most important directories in the OpenRocket core and swing modules.

This page walks through the most important packages in the info.openrocket.core and info.openrocket.swing modules. Use it to orient yourself when exploring the codebase.

Module folder structure

Both modules follow the standard Gradle source layout:

<module>/
├── gradle/                  # Gradle wrapper
├── libs/                    # Local JAR files not available in Maven repositories
├── resources-src/           # Source files for resources (e.g. Inkscape source for splash screen)
├── scripts/                 # Utility scripts
├── src/
│   ├── main/
│   │   ├── java/            # Java source code
│   │   └── resources/       # Resource files (images, config, data files)
│   └── test/
│       ├── java/            # Java test source code
│       └── resources/       # Test resource files
└── src-extra/               # Extra source not part of the main application (e.g. plugin templates)

Core module

The core module source lives at core/src/main/java/info/openrocket/core/. The following table describes the main packages:

aerodynamics — aerodynamic force and coefficient calculations

Calculates aerodynamic properties such as drag coefficient (CD), center of pressure (CP), and aerodynamic forces acting on the rocket during flight.

• aerodynamics/barrowman/ — Implementation of the extended Barrowman method for calculating CP and aerodynamic coefficients for each component type.

appearance — component visual appearance

Handles the visual appearance of rocket components in the 3D view, including paint color, transparency, shine, and texture decals.

• appearance/defaults/ — Default appearance settings applied when no custom appearance is configured.

communication — external communication

Communicates with external services, for example checking GitHub for the latest OpenRocket release version.

database — component and motor databases

Manages the component preset database and the motor thrust curve database.

• database/motor/ — Motor (thrust curve) database loading and lookup.

document — OpenRocket document model

Represents an open OpenRocket document, which contains the rocket design plus all simulations. Handles change notifications and undo/redo state.

• document/attachments/ — File attachments embedded in a document.
• document/events/ — Events fired when a document or simulation changes.

file — file format parsers and writers

Contains all file I/O code. Each supported format has its own sub-package.

Sub-package	Format
file/openrocket/importt/	Read .ork files
file/openrocket/savers/	Write .ork files
file/rasaero/importt/	Import RASAero II files
file/rasaero/export/	Export to RASAero II
file/rocksim/importt/	Import RockSim files
file/rocksim/export/	Export to RockSim
file/motor/	Motor file handling
file/svg/export/	SVG export
file/wavefrontobj/export/	Wavefront OBJ 3D export
file/simplesax/	SAX XML utility
file/iterator/	Iterate files in directories or ZIP archives

l10n — localization

Provides translation support for the OpenRocket user interface. Translations are stored as .properties files in the swing module’s resources.

logging — errors, warnings, and diagnostics

OpenRocket’s internal diagnostic logging layer, separate from the SLF4J application logging. Records errors, warnings, and simulation aborts for display to users.

masscalc — mass and inertia calculations

Mass property calculation drivers: total mass, center of gravity (CG), and moments of inertia. The actual per-component mass calculations live in the component classes themselves.

material — material physical properties

Defines the material property model (density, type) used throughout the component editor and aerodynamic calculations.

models — physical environment models

Pluggable models for the physical environment during simulation.

• models/atmosphere/ — Atmosphere models (e.g., International Standard Atmosphere).
• models/gravity/ — Gravity models.
• models/wind/ — Wind models, including average wind and multi-level wind profiles.

motor — motor configuration and thrust curves

Motor identity, configuration, and thrust curve data structures. Separate from the database lookup code in database/motor/.

optimization — trajectory optimization engine

Optimization algorithms and rocket-specific optimization framework.

• optimization/general/multidim/ — Multidimensional parallel search.
• optimization/general/onedim/ — One-dimensional golden-section search.
• optimization/rocketoptimization/ — Rocket parameter optimization for specified goals (max altitude, max velocity, etc.).

preset — component preset database

Defines the ComponentPreset model and handles loading/saving of .orc component database files.

• preset/loader/ — Loads component database files.
• preset/xml/ — JAXB-based XML serialization of component presets.

rocketcomponent — rocket component model

The heart of the core module. Contains the class hierarchy for every type of rocket component: NoseCone, BodyTube, TrapezoidFinSet, Parachute, and so on. All components extend RocketComponent.

• rocketcomponent/position/ — Component positioning logic (axial offset, radial offset).

simulation — flight simulation engine

The simulation engine that computes the rocket’s flight trajectory.

• simulation/customexpression/ — User-defined custom simulation output expressions.
• simulation/extension/ — Simulation extension API and example extensions.
• simulation/listeners/ — Listener interface that hooks into the simulation at each time step.
• simulation/listeners/system/ — Built-in listeners used internally by OpenRocket.

thrustcurve — ThrustCurve.org API and serialization

Fetches motor data from ThrustCurve.org and serializes it into the SQLite database bundled with OpenRocket. The serializeEngines Gradle task runs the serialization.

unit — unit definitions and conversions

Defines Unit (a single unit with SI conversion methods) and UnitGroup (a measurable quantity with multiple available units). All display-facing value formatting goes through this package.

util / utils — utility methods

Miscellaneous utility classes. util/enums/ provides enum-to-name conversion helpers.

Swing module

The swing module source lives at swing/src/main/java/info/openrocket/swing/. The following table describes the main packages:

gui/main — main application window

The top-level application window, toolbar, and main panel.

• gui/main/componenttree/ — The rocket component tree panel shown on the left side of the main window.
• gui/main/flightconfigpanel/ — The flight configuration panel for managing motor configurations.

gui/configdialog — component configuration dialogs

The configuration dialogs that open when you double-click a rocket component. Each dialog presents the editable properties for a component type.

gui/rocketfigure — 2D rocket cross-section rendering

Renders the 2D side-view and cross-section figures of the rocket. Each component type provides a RocketComponentShapeService implementation that knows how to draw itself.

gui/figure3d — 3D rocket visualization

OpenGL-based 3D rendering of the rocket using JOGL.

• gui/figure3d/photo/ — PhotoStudio mode with exhaust, smoke, sparks, and sky rendering.

gui/plot — simulation results plots

JFreeChart-based plots of simulation output data (altitude, velocity, acceleration, etc.).

gui/dialogs — various dialogs

Contains the many dialog windows in OpenRocket:

• gui/dialogs/motor/thrustcurve/ — Motor selection and thrust curve browser.
• gui/dialogs/optimization/ — Rocket optimization dialog.
• gui/dialogs/preferences/ — Application preferences dialog.
• gui/dialogs/preset/ — Component preset selection dialog.
• gui/dialogs/flightconfiguration/ — Flight configuration management.

gui/theme — UI theming

FlatLaf-based theming support. Theme property files live in swing/src/main/resources/themes/ (e.g. FlatLafLight.properties, FlatDarculaLaf.properties). Custom keys are prefixed with OR. and read via UIManager in UITheme.java.

gui/components — reusable Swing components

Reusable custom Swing widgets used throughout the application, including a compass rose component.

gui/adaptors — model adaptors

Bridges between the core data model and Swing model interfaces (e.g., TableModel, SpinnerModel). Keeps GUI code decoupled from the domain model.

startup — application entry point and Guice wiring

Contains SwingStartup, the main entry point for the desktop application. Sets up the Guice injector and launches the main window.

• startup/providers/ — Guice provider classes.
• startup/jij/ — JAR-in-JAR class loading support.

simulation/extension — Swing-side simulation extensions

The Swing UI side of the simulation extension system. Provides the configuration panels for built-in simulation extensions.

UI theming notes

OpenRocket uses FlatLaf property files for UI colors and other defaults. To add or modify a theme value:

1. Edit the relevant OR.* key in each theme file under swing/src/main/resources/themes/. Keep all variants (light, Darcula, One Dark) in sync.
2. Add a corresponding lookup in UITheme.Keys in swing/src/main/java/info/openrocket/swing/gui/theme/UITheme.java.
3. Test by switching themes in Preferences — properties are applied when UITheme.applyTheme runs.

Input validation

For immediate visual feedback on invalid inputs, use FlatLafOutlines rather than ad-hoc putClientProperty calls:

// Simple outline
FlatLafOutlines.setOutline(myComponent, FlatLafOutlines.Outline.WARNING);

// Live validation with conditions
FlatLafOutlines.validator(mySpinner)
    .warnIf(() -> suspiciousValue(), () -> trans.get("my.warning.key"))
    .errorIf(() -> invalidValue(), () -> trans.get("my.error.key"))
    .showMessagePopup(2500)
    .listenTo(model1, model2);

Use warnIf for “dubious but allowed” values and errorIf for values that should block confirmation.