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UI Module

Lagrange UI module is a mini 3D engine C++ library built on top of EnTT.

Prerequistes

Must have OpenGL 3.3 capable drivers and a windowing system (headless is not supported). To use the library, enable LAGRANGE_MODULE_UI in CMake and

#include <lagrange/ui/UI.h>
namespace ui = lagrange::ui;

Overview

Lagrange UI uses an Entity-Component-System (ECS) architecture:

  • Entity is a unique identifier
  • Components define data and behavior (but no logic)
  • Systems define logic (but no data).

See ECS implementation section for more information about ECS and how it's implemented in Lagrange UI. The underlying library for ECS is EnTT.

The entry point to the library is the Viewer class. It instantiates a window and owns a Registry instance and Systems instance. Registry contains all the data (entities and components) and Systems contain all the behavior (sequence of functions that is called every frame). To start the UI:

ui::Viewer viewer;
viewer.run([](){
    //Main loop code
});

//Or

viewer.run([](ui::Registry & r){
    //Main loop code
    return should_continue_running;
});

The API to interact with the UI follows the pattern: 

ui::Entity entity = ui::do_something(registry, params)
SomeData & data = registry.get<SomeData>(entity);

For example: 

//Loads mesh from path
ui::Entity mesh_geometry = ui::load_mesh(registry, path);

//Adds the mesh to scene
ui::Entity mesh_visualization = ui::show_mesh(registry, mesh_geometry);

//Retrieves Transform component of the visualized mesh
Transform & transform = registry.get<Transform>(mesh_visualization);

All entities and their components live in a Registry. To access/set/modify the entities and components, use the Viewer::registry(). 

auto & registry = viewer.registry();
auto entity = registry.create();
registry.emplace<MyPositionComponent>(entity, MyPositionComponent(0,0,0));

Note

You can use Viewer class as an argument instead of Registry, e.g.: 

Viewer v;
auto mesh_geometry = ui::load_mesh(v, path);

Further Documentation

Doxygen generated documentation