Entity Component Systems

ecs.md

Entity Component Systems

collecting links and documents about the topic

Articles

Object Systems (2004, as used in Thief 1998) http://chrishecker.com/images/6/6f/ObjSys.ppt

A Data Driven Game Object System (GDC 2002) http://scottbilas.com/files/2002/gdc_san_jose/game_objects_slides_with_notes.pdf

A Dynamic Component Architecture for High Performance Gameplay (GDC 2010) http://www.insomniacgames.com/a-dynamic-component-architecture-for-high-performance-gameplay/

Building a Data-Oriented Entity System (C++, 2014) http://bitsquid.blogspot.com.au/2014/08/building-data-oriented-entity-system.html http://bitsquid.blogspot.com.au/2014/09/building-data-oriented-entity-system.html http://bitsquid.blogspot.com.au/2014/10/building-data-oriented-entity-system.html http://bitsquid.blogspot.com.au/2014/10/building-data-oriented-entity-system_10.html

Comparison of Doom 1, Quake, and Doom 3 entity references system http://blog.noctua-software.com/entity-references.html

Adam Martin. Entity Systems are the future of MMOG development http://t-machine.org/index.php/2007/09/03/entity-systems-are-the-future-of-mmog-development-part-1/, 2007

Jeff Plummer. A flexible and expandable architecture for computer games https://www.tjhsst.edu/~rlatimer/techlab07/plummer_thesis.pdf , 2004

The Components and Systems of Morgan's Raid http://paulgestwicki.blogspot.ru/2012/03/components-and-systems-of-morgans-raid.html

Dungeon Siege https://web.archive.org/web/20150418070828/http://scottbilas.com/games/dungeon-siege

Data Structures for Entity Systems: Contiguous memory http://t-machine.org/index.php/2014/03/08/data-structures-for-entity-systems-contiguous-memory/

Implementations

Artemis-odb a high performance java based Entity-Component-System framework https://github.com/junkdog/artemis-odb

Adam Martin. Entity Systems are the future of MMOG development http://t-machine.org/index.php/2007/09/03/entity-systems-are-the-future-of-mmog-development-part-1/, 2007

Jeff Plummer. A flexible and expandable architecture for computer games
https://www.tjhsst.edu/~rlatimer/techlab07/plummer_thesis.pdf , 2004

The Components and Systems of Morgan's Raid http://paulgestwicki.blogspot.ru/2012/03/components-and-systems-of-morgans-raid.html

Dungeon Siege https://web.archive.org/web/20150418070828/http://scottbilas.com/games/dungeon-siege

Some food for thought on "low memory usage, cache friendliness, O(1) access, that sort of stuff" http://t-machine.org/index.php/2014/03/08/data-structures-for-entity-systems-contiguous-memory/

Top of the list: recycle int entity ids, and make sure that component types can be represented by an int too - this opens up to using ids as indices into component arrays, and bitsets can be used in a lot of places - primarily as fast lookup caches.

artemis-odb has a lot java specific stuff, but it does a couple of things I haven't seen elsewhere in open source land:

• entity subscriptions - i.e. a view of all entities matching a certain component composition - should be interactable from outside systems. Good for stuff like bootstrapping entities etc ("transient" components, like textures, can't be serialized, but this approach makes a generic serialization approach pretty easy):

world.getAspectSubscriptionManager()
    .get(all(Size.class, TextureReference.class).exclude(Renderable.class))
    .addSubscriptionListener(
        new SubscriptionAdapter(world) {
            @Override
            protected void inserted(Entity e) {
                assignRenderable(e);
            }
    });

• identify entity compositions as an id, not as a set of bitsets as is commonly done: enables very fast insertions and removals from systems. http://gamedev.stackexchange.com/a/102691/16250