Heraclitus of Ephesus (/ˌhɛrəˈklaɪtəs/;[1] Greek: Ἡράκλειτος ὁ Ἐφέσιος Hērákleitos ho Ephésios; c. 535 – c. 475 BC) was a pre-Socratic Greek philosopher, and a native of the city of Ephesus,[2] then part of the Persian Empire.

Heraclitus was famous for his insistence on ever-present change as being the fundamental essence of the universe, as stated in the famous saying, "No man ever steps in the same river twice"[6] (see panta rhei below). This position was complemented by his stark commitment to a unity of opposites in the world, stating that "the path up and down are one and the same". Through these doctrines Heraclitus characterized all existing entities by pairs of contrary properties, whereby no entity may ever occupy a single state at a single time. This, along with his cryptic utterance that "all entities come to be in accordance with this Logos " (literally, "word", "reason", or "account") has been the subject of numerous interpretations.

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0. What is it?

A game engine written in Go.

1. Development

Run make to build and test.

Dependencies can be installed by make deps.

2. Dependencies

apt:

• libsdl2{,-mixer,-image,-ttf,-gfx}-dev

pacman:

• sdl2{,_mixer,_image,_ttf,_gfx}

windows: mingw env packages (install from source)

• SDL2-devel-2.0.5-mingw.tar.gz
• SDL2_image-devel-2.0.1-mingw.tar.gz
• SDL2_mixer-devel-2.0.1-mingw.tar.gz
• SDL2_ttf-devel-2.0.14-mingw.tar.gz

3. Technical details

3.a. General engine design

3.a.i. entity component system

The engine is built on an "entity-component-system" architecture, in which:

Components are collections of a certain type of data indexed by the ID's of entities. For example, the velocity component is a [MAX_ENTITIES]Vec2D. -- see component_table.go

Entities are conceptually an ID which indexes the component data, and Logics that run every World.Update(), and Funcs that can be called by string-name (entities can be active or inactive) -- see entity.go

Systems are collections of logic which run every World.Update() and usually operate on subsets of entities selected for by an arbitrary query -- see collision_system.go for an example system (Users can also define and provide their own systems by implementing the System interface)

There are also some Managers which are sort of like the glue holding the engine together, or providing services.

The EntityManager is a particularly important central part of the engine. - see entity_manager.go, entity_manager_spawn.go, etc.

3.a.ii. scenes

The engine is also built on a "scene-based" architecture, in which:

Scenes are loaded into the Game object's loop, and have control over input and display while they're running.

All scenes will be registered and stored with the singleton Game object, and can refer to each other by name (strings).

The currently running scene is updated each game loop iteration, receiving:

• keyboard state via a call to a HandleKeyboardState (keyboard_state []uint8) method
• delta-time updates via a call to an Update (dt_ms float64, allowance_ms float64) method (allowance_ms should be passed to World.Update() if this scene is using a World)
• a call to a Draw (window *sdl.Window, renderer *sdl.Renderer) method.

Scenes are initialized and loaded in the background while a singleton loading scene will be displayed until the new scene is ready to take over.

3.a.iii. worlds

Worlds are where the magic actually happens.

You call World.RegisterComponents() and World.RegisterSystems() to set up the entity-components and the systems that will run.

You can call World.AddLogic() to add world logic funcs (Logic funcs will receive (dt_ms float64) where dt_ms is the ms since the func last ran)

Your scene should call World.Update(allowance_ms) every Scene.Update().

See world.go for the full suite of functions available.