EnTT
is a header-only, tiny and easy to use library for game programming and
much more written in modern C++, mainly known for its innovative
entity-component-system (ECS) model.
Among others, it's used
in Minecraft by Mojang and the
ArcGIS Runtime SDKs by
Esri.
If you don't see your project in the list, please open an issue, submit a PR or
add the #entt tag to your topics! ๐
Do you want to keep up with changes or do you have a question that
doesn't require you to open an issue?
Join the gitter channel or the
discord server and meet other users like you. The
more we are, the better for everyone.
Wondering why your debug build is so slow on Windows or how to represent a
hierarchy with components?
Check out the
FAQ and the
wiki if you have these or other doubts,
your answers may already be there.
If you use EnTT
and you want to say thanks or support the project, please
consider becoming a
sponsor.
You can help me make the difference.
Many thanks to those who supported me
and still support me today.
The entity-component-system (also known as ECS) is an architectural pattern used mostly in game development. For further details:
This project started off as a pure entity-component system. Over time the
codebase has grown as more and more classes and functionalities were added.
Here is a brief, yet incomplete list of what it offers today:
- Statically generated integer identifiers for types (assigned either at compile-time or at runtime).
- A
constexpr
utility for human readable resource names. - A minimal configuration system built using the monostate pattern.
- An incredibly fast entity-component system based on sparse sets, with its own pay for what you use policy to adjust performance and memory usage according to the users' requirements.
- Views and groups to iterate entities and components and allow different access patterns, from perfect SoA to fully random.
- A lot of facilities built on top of the entity-component system to help the users and avoid reinventing the wheel (dependencies, snapshot, actor class, support for reactive systems and so on).
- The smallest and most basic implementation of a service locator ever seen.
- A built-in, non-intrusive and macro-free runtime reflection system.
- A cooperative scheduler for processes of any type.
- All that is needed for resource management (cache, loaders, handles).
- Delegates, signal handlers (with built-in support for collectors) and a tiny event dispatcher for immediate and delayed events to integrate in loops.
- A general purpose event emitter as a CRTP idiom based class template.
- And much more! Check out the wiki.
Consider this list a work in progress as well as the project. The whole API is fully documented in-code for those who are brave enough to read it.
Currently, EnTT
is tested on Linux, Microsoft Windows and OSX. It has proven
to work also on both Android and iOS.
Most likely it won't be problematic on other systems as well, but it hasn't been
sufficiently tested so far.
#include <entt/entt.hpp>
#include <cstdint>
struct position {
float x;
float y;
};
struct velocity {
float dx;
float dy;
};
void update(entt::registry ®istry) {
auto view = registry.view<position, velocity>();
for(auto entity: view) {
// gets only the components that are going to be used ...
auto &vel = view.get<velocity>(entity);
vel.dx = 0.;
vel.dy = 0.;
// ...
}
}
void update(std::uint64_t dt, entt::registry ®istry) {
registry.view<position, velocity>().each([dt](auto &pos, auto &vel) {
// gets all the components of the view at once ...
pos.x += vel.dx * dt;
pos.y += vel.dy * dt;
// ...
});
}
int main() {
entt::registry registry;
std::uint64_t dt = 16;
for(auto i = 0; i < 10; ++i) {
auto entity = registry.create();
registry.emplace<position>(entity, i * 1.f, i * 1.f);
if(i % 2 == 0) { registry.emplace<velocity>(entity, i * .1f, i * .1f); }
}
update(dt, registry);
update(registry);
// ...
}
I started developing EnTT
for the wrong reason: my goal was to design an
entity-component system to beat another well known open source solution both in
terms of performance and possibly memory usage.
In the end, I did it, but it wasn't very satisfying. Actually it wasn't
satisfying at all. The fastest and nothing more, fairly little indeed. When I
realized it, I tried hard to keep intact the great performance of EnTT
and to
add all the features I wanted to see in my own library at the same time.
Nowadays, EnTT
is finally what I was looking for: still faster than its
competitors, lower memory usage in the average case, a really good API and an
amazing set of features. And even more, of course.
The proposed entity-component system is incredibly fast to iterate entities and
components, this is a fact. Some compilers make a lot of optimizations because
of how EnTT
works, some others aren't that good. In general, if we consider
real world cases, EnTT
is somewhere between a bit and much faster than many of
the other solutions around, although I couldn't check them all for obvious
reasons.
If you are interested, you can compile the benchmark
test in release mode (to
enable compiler optimizations, otherwise it would make little sense) by setting
the BUILD_BENCHMARK
option of CMake
to ON
, then evaluate yourself whether
you're satisfied with the results or not.
Honestly I got tired of updating the README file whenever there is an
improvement.
There are already a lot of projects out there that use EnTT
as a basis for
comparison (this should already tell you a lot). Many of these benchmarks are
completely wrong, many others are simply incomplete, good at omitting some
information and using the wrong function to compare a given feature. Certainly
there are also good ones but they age quickly if nobody updates them, especially
when the library they are dealing with is actively developed.
The choice to use EnTT
should be based on its carefully designed API, its
set of features and the general performance, not because some single
benchmark shows it to be the fastest tool available.
In the future I'll likely try to get even better performance while still adding
new features, mainly for fun.
If you want to contribute and/or have suggestions, feel free to make a PR or
open an issue to discuss your idea.
To be able to use EnTT
, users must provide a full-featured compiler that
supports at least C++17.
The requirements below are mandatory to compile the tests and to extract the
documentation:
CMake
version 3.7 or later.Doxygen
version 1.8 or later.
Alternatively, Bazel is also supported as a build system
(credits to zaucy who offered to maintain it).
In the documentation below I'll still refer to CMake
, this being the official
build system of the library.
If you are looking for a C++14 version of EnTT
, check out the git tag cpp14
.
EnTT
is a header-only library. This means that including the entt.hpp
header
is enough to include the library as a whole and use it. For those who are
interested only in the entity-component system, consider to include the sole
entity/registry.hpp
header instead.
It's a matter of adding the following line to the top of a file:
#include <entt/entt.hpp>
Use the line below to include only the entity-component system instead:
#include <entt/entity/registry.hpp>
Then pass the proper -I
argument to the compiler to add the src
directory to
the include paths.
The documentation is based on doxygen. To build it:
$ cd build
$ cmake .. -DBUILD_DOCS=ON
$ make
The API reference will be created in HTML format within the directory
build/docs/html
. To navigate it with your favorite browser:
$ cd build
$ your_favorite_browser docs/html/index.html
It's also available online for the latest
version, that is the last stable tag.
Moreover, there exists a wiki dedicated
to the project where users can find all related documentation pages.
To compile and run the tests, EnTT
requires googletest.
cmake
will download and compile the library before compiling anything else.
In order to build the tests, set the CMake option BUILD_TESTING
to ON
.
To build the most basic set of tests:
$ cd build
$ cmake -DBUILD_TESTING=ON ..
$ make
$ make test
Note that benchmarks are not part of this set.
EnTT
is available for some of the most known packaging tools. In particular:
-
Conan
, the C/C++ Package Manager for Developers. -
vcpkg
, Microsoft VC++ Packaging Tool.
You can download and installEnTT
in just a few simple steps:$ git clone https://github.com/Microsoft/vcpkg.git $ cd vcpkg $ ./bootstrap-vcpkg.sh $ ./vcpkg integrate install $ vcpkg install entt
The
EnTT
port invcpkg
is kept up to date by Microsoft team members and community contributors.
If the version is out of date, please create an issue or pull request on thevcpkg
repository. -
Homebrew
, the missing package manager for macOS.
Available as a homebrew formula. Just type the following to install it:brew install skypjack/entt/entt
-
build2
, build toolchain for developing and packaging C and C++ code.
In order to use theentt
package in abuild2
project, add the following line or a similar one to themanifest
file:depends: entt ^3.0.0
Also check that the configuration refers to a valid repository, so that the package can be found by
build2
:-
cppget.org
, the open-source community central repository, accessible as https://pkg.cppget.org/1/stable -
Package source repository: accessible as either https://github.com/build2-packaging/entt.git or ssh://[email protected]/build2-packaging/entt.git Feel free to report issues with this package.
Both can be used with
bpkg add-repo
or added in a projectrepositories.manifest
. See the official documentation for more details. -
Consider this list a work in progress and help me to make it longer.
EnTT
is widely used in private and commercial applications. I cannot even
mention most of them because of some signatures I put on some documents time
ago. Fortunately, there are also people who took the time to implement open
source projects based on EnTT
and did not hold back when it came to
documenting them.
Here you can find an incomplete list of games, applications and articles that can be used as a reference.
If you know of other resources out there that are about EnTT
, feel free to
open an issue or a PR and I'll be glad to add them to the list.
EnTT
was written initially as a faster alternative to other well known and
open source entity-component systems. Nowadays this library is moving its first
steps. Much more will come in the future and hopefully I'm going to work on it
for a long time.
Requests for features, PR, suggestions ad feedback are highly appreciated.
If you find you can help me and want to contribute to the project with your
experience or you do want to get part of the project for some other reasons,
feel free to contact me directly (you can find the mail in the
profile).
I can't promise that each and every contribution will be accepted, but I can
assure that I'll do my best to take them all seriously.
If you decide to participate, please see the guidelines for
contributing before to create issues or pull
requests.
Take also a look at the
contributors list to
know who has participated so far.
Code and documentation Copyright (c) 2017-2020 Michele Caini.
Logo Copyright (c) 2018-2020 Richard Caseres.
Code released under
the MIT license.
Documentation released under
CC BY 4.0.
Logo released under
CC BY-SA 4.0.
If you want to support this project, you can
offer me an espresso.
If you find that it's not enough, feel free to
help me the way you prefer.