Crate heron

Expand description

An ergonomic physics API for 2d and 3d bevy games. (powered by rapier)

Get started

Add the dependency and choose to work with either 2d or 3d

Add the library to Cargo.toml.

For a 3d game:

heron = { version = "3", features = ["3d"] }

For as 2d game:

heron = { version = "3", features = ["2d"] }

Feature flags

One must choose to use either 2d or 3d. If none of theses two features is enabled, the plugin won’t be available.

3d Enable simulation on the 3 axes x, y, and z. Incompatible with the feature 2d.
2d Enable simulation only on the first 2 axes x and y. Incompatible with the feature 3d, therefore require to disable the default features.
debug-2d Render 2d collision shapes
debug-3d Render 3d collision shapes
collision-from-mesh Add the PendingConvexCollision component to generate convex hull collision shapes from a mesh
enhanced-determinism Enable rapier’s enhanced-determinism

Install the plugin

The PhysicsPlugin should be installed to enable physics and collision detection.

use bevy::prelude::*;
use heron::prelude::*;

fn main() {
  App::new()
    .add_plugins(DefaultPlugins)
    .add_plugin(PhysicsPlugin::default())
    // ... Add your resources and systems
    .run();
}

Create rigid bodies

To create a rigid body, add the RigidBody to the entity and add a collision shapes with the CollisionShape component.

The position and rotation are defined by the bevy GlobalTransform component.

fn spawn(mut commands: Commands) {
commands

    // Spawn any bundle of your choice. Only make sure there is a `GlobalTransform`
    .spawn_bundle(SpriteBundle::default())

    // Make it a rigid body
    .insert(RigidBody::Dynamic)

    // Attach a collision shape
    .insert(CollisionShape::Sphere { radius: 10.0 })

    // Optionally add other useful components...
    .insert(Velocity::from_linear(Vec3::X * 2.0))
    .insert(Acceleration::from_linear(Vec3::X * 1.0))
    .insert(PhysicMaterial { friction: 1.0, density: 10.0, ..Default::default() })
    .insert(RotationConstraints::lock());
}

Move rigid bodies programmatically

When creating games, it is often useful to interact with the physics engine and move bodies programmatically. For this, you have two options: Updating the Transform or applying a Velocity.

Option 1: Update the Transform

For positional kinematic bodies (RigidBody::KinematicPositionBased), if the transform is updated, the body is moved and get an automatically calculated velocity. Physics rules will be applied normally. Updating the transform is a good way to move a kinematic body.

For other types of bodies, if the transform is updated, the rigid body will be teleported to the new position/rotation, ignoring physic rules.

Option 2: Use the Velocity component

For RigidBody::Dynamic and RigidBody::KinematicVelocityBased bodies only, one can add a Velocity component to the entity, that will move the body over time. Physics rules will be applied normally.

Note that the velocity component is updated by heron to always reflects the current velocity.

Defining/updating the velocity is a good way to interact with dynamic bodies.