EnTT is a header-only, tiny and easy to use library for game programming and
much more written in modern C++.
Among others, it's used
in Minecraft by Mojang, the
ArcGIS Runtime SDKs by Esri
and the amazing Ragdoll.
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! 👍
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 and the
discord server, meet other users like you. The
more we are, the better for everyone.
Don't forget to check the
FAQs and the
wiki too. Your answers may already be
there.
Do you want to support EnTT? Consider becoming a
sponsor.
Many thanks to these people and
special thanks to:
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
constexprutility 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, handles, 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.
- Static polymorphism made simple and within everyone's reach.
- 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.
It is also known that EnTT is used in Minecraft.
Given that the game is available literally everywhere, I can confidently say
that the library has been sufficiently tested on every platform that can come to
mind.
#include <entt/entt.hpp>
struct position {
float x;
float y;
};
struct velocity {
float dx;
float dy;
};
void update(entt::registry ®istry) {
auto view = registry.view<const position, velocity>();
// use a callback
view.each([](const auto &pos, auto &vel) { /* ... */ });
// use an extended callback
view.each([](const auto entity, const auto &pos, auto &vel) { /* ... */ });
// use a range-for
for(auto [entity, pos, vel]: view.each()) {
// ...
}
// use forward iterators and get only the components of interest
for(auto entity: view) {
auto &vel = view.get<velocity>(entity);
// ...
}
}
int main() {
entt::registry registry;
for(auto i = 0u; i < 10u; ++i) {
const 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(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 ENTT_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.
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.
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:
CMakeversion 3.7 or later.Doxygenversion 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.
To use EnTT from a CMake project, just link an existing target to the
EnTT::EnTT alias.
The library offers everything you need for locating (as in find_package),
embedding (as in add_subdirectory), fetching (as in FetchContent) or using
it in many of the ways that you can think of and that involve CMake.
Covering all possible cases would require a treaty and not a simple README file,
but I'm confident that anyone reading this section also knows what it's about
and can use EnTT from a CMake project without problems.
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 installEnTTin just a few simple steps:$ git clone https://github.com/Microsoft/vcpkg.git $ cd vcpkg $ ./bootstrap-vcpkg.sh $ ./vcpkg integrate install $ vcpkg install enttOr you can use the
experimentalfeature to test the latest changes:vcpkg install entt[experimental] --headThe
EnTTport invcpkgis 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 thevcpkgrepository. -
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 theenttpackage in abuild2project, add the following line or a similar one to themanifestfile:depends: entt ^3.0.0Also 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 ashttps://pkg.cppget.org/1/stable. -
Package source repository: accessible as either
https://github.com/build2-packaging/entt.gitorssh://[email protected]/build2-packaging/entt.git. Feel free to report issues with this package.
Both can be used with
bpkg add-repoor 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 if you like.
EnTT also supports pkg-config (for some definition of supports at least).
A suitable file called entt.pc is generated and installed in a proper
directory when running CMake.
This should also make it easier to use with tools such as Meson or similar.
The documentation is based on doxygen. To build it:
$ cd build
$ cmake .. -DENTT_BUILD_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
The same version is also available online
for the latest release, that is the last stable tag. If you are looking for
something more pleasing to the eye, consider reading the nice-looking version
available on docsforge: same documentation, much
more pleasant to read.
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 ENTT_BUILD_TESTING to
ON.
To build the most basic set of tests:
$ cd build$ cmake -DENTT_BUILD_TESTING=ON ..$ make$ make test
Note that benchmarks are not part of this set.
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.
Requests for features, PRs, suggestions ad feedback are highly appreciated.
If you find you can help and want to contribute to the project with your
experience or you do want to get part of the project for some other reason, 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 as soon as possible.
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) 2017-2021 Michele Caini.
Colorful logo Copyright (c) 2018-2021 Richard Caseres.
Code released under
the MIT license.
Documentation released under
CC BY 4.0.
All logos released under
CC BY-SA 4.0.