big-brain
big-brain is a Utility
AI library for games, built
for the Bevy Game Engine
It lets you define complex, intricate AI behaviors for your entities based on their perception of the world. Definitions are heavily data-driven, using plain Rust, and you only need to program Scorers (entities that look at your game world and come up with a Score), and Actions (entities that perform actual behaviors upon the world). No other code is needed for actual AI behavior.
See the documentation for more details.
Features
- Highly concurrent/parallelizable evaluation.
- Integrates smoothly with Bevy.
- Proven game AI model.
- Highly composable and reusable.
- State machine-style continuous actions/behaviors.
- Action cancellation.
Example
As a developer, you write application-dependent code to define
Scorers and Actions, and then put it all
together like building blocks, using Thinkers that will
define the actual behavior.
Scorers
Scorers are entities that look at the world and evaluate into Score
values. You can think of them as the "eyes" of the AI system. They're a
highly-parallel way of being able to look at the World and use it to
make some decisions later.
use bevy::prelude::*;
use big_brain::prelude::*;
#[derive(Debug, Clone, Component, ScorerBuilder)]
pub struct Thirsty;
pub fn thirsty_scorer_system(
thirsts: Query<&Thirst>,
mut query: Query<(&Actor, &mut Score), With<Thirsty>>,
) {
for (Actor(actor), mut score) in query.iter_mut() {
if let Ok(thirst) = thirsts.get(*actor) {
score.set(thirst.thirst);
}
}
}Actions
Actions are the actual things your entities will do. They are
connected to ActionStates that represent the current execution state of
the state machine.
use bevy::prelude::*;
use big_brain::prelude::*;
#[derive(Debug, Clone, Component, ActionBuilder)]
pub struct Drink;
fn drink_action_system(
mut thirsts: Query<&mut Thirst>,
mut query: Query<(&Actor, &mut ActionState), With<Drink>>,
) {
for (Actor(actor), mut state) in query.iter_mut() {
if let Ok(mut thirst) = thirsts.get_mut(*actor) {
match *state {
ActionState::Requested => {
thirst.thirst = 10.0;
*state = ActionState::Success;
}
ActionState::Cancelled => {
*state = ActionState::Failure;
}
_ => {}
}
}
}
}Thinkers
Finally, you can use it when define the Thinker, which you can attach as
a regular Component:
fn spawn_entity(cmd: &mut Commands) {
cmd.spawn((
Thirst(70.0, 2.0),
Thinker::build()
.picker(FirstToScore { threshold: 0.8 })
.when(Thirsty, Drink),
));
}App
Once all that's done, we just add our systems and off we go!
fn main() {
App::new()
.add_plugins(DefaultPlugins)
.add_plugin(BigBrainPlugin)
.add_startup_system(init_entities)
.add_system(thirst_system)
.add_system_to_stage(BigBrainStage::Actions, drink_action_system)
.add_system_to_stage(BigBrainStage::Scorers, thirsty_scorer_system)
.run();
}bevy version
The current version of big-brain is compatible with bevy 0.9.0.
Contributing
- Install the latest Rust toolchain (stable supported).
cargo run --example thirst- Happy hacking!
License
This project is licensed under the Apache-2.0 License.