avian3d-sandbox/src/bike.rs

use avian3d::{
    math::{Scalar, FRAC_PI_2},
    prelude::*,
};
use bevy::prelude::*;

use crate::physics::CatControllerState;

pub const SPRING_CONSTANT: Scalar = 60.0;
pub const DAMPING_CONSTANT: Scalar = 10.0;
pub const WHEEL_RADIUS: Scalar = 0.4;
pub const REST_DISTANCE: Scalar = 1.5 + WHEEL_RADIUS;
pub const FRICTION_COEFF: Scalar = 0.9;
pub const FRONT_ATTACH: Vec3 = Vec3::new(0.0, 0.0, -0.5);
pub const REAR_ATTACH: Vec3 = Vec3::new(0.0, 0.0, 0.5);

#[derive(Component)]
pub struct CyberBikeBody;

#[derive(Component, Clone, Copy, Debug)]
pub enum CyberWheel {
    Front,
    Rear,
}

#[derive(Component, Clone, Copy, Debug, Reflect, Default)]
#[reflect(Component)]
pub struct WheelState {
    pub displacement: Scalar,
    pub force_normal: Scalar,
    pub sliding: bool,
    pub contact_point: Option<Vec3>,
    pub contact_normal: Option<Vec3>,
}

impl WheelState {
    pub fn reset(&mut self) {
        *self = Self::default();
    }
}

#[derive(Component, Clone, Copy, Debug, Reflect)]
#[reflect(Component)]
#[require(WheelState)]
pub struct WheelConfig {
    pub attach: Vec3,
    pub rest_dist: Scalar,
    pub konstant: Scalar,
    pub damping: Scalar,
    pub friction: Scalar,
    pub radius: Scalar,
}

impl WheelConfig {
    fn new(
        attach: Vec3,
        rest_dist: Scalar,
        konstant: Scalar,
        damping: Scalar,
        friction: Scalar,
        radius: Scalar,
    ) -> Self {
        WheelConfig {
            attach,
            rest_dist,
            konstant,
            damping,
            friction,
            radius,
        }
    }
}

fn spawn_bike(
    mut commands: Commands,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<StandardMaterial>>,
) {
    let pos = Vec3::new(0.0, 5.0, 0.0);
    let xform = Transform::from_translation(pos); //.with_rotation(Quat::from_rotation_z(0.0));

    let body_collider =
        Collider::capsule_endpoints(0.5, Vec3::new(0.0, 0.0, -0.65), Vec3::new(0.0, 0.0, 0.8));

    commands
        .spawn((xform, Visibility::default()))
        .insert((
            Name::new("body"),
            RigidBody::Dynamic,
            body_collider,
            CollisionLayers::from_bits(1, 1),
            SleepingDisabled,
            CyberBikeBody,
            CatControllerState::default(),
            ColliderDensity(1.2),
            AngularDamping(0.2),
            LinearDamping(0.1),
            ExternalForce::ZERO.with_persistence(false),
            ExternalTorque::ZERO.with_persistence(false),
        ))
        .with_children(|builder| {
            let color = Color::srgb(0.7, 0.05, 0.7);
            let mut xform = Transform::default();
            xform.rotate_x(FRAC_PI_2);
            let pbr_bundle = (
                Mesh3d(meshes.add(Capsule3d::new(0.5, 1.45))),
                xform,
                MeshMaterial3d(materials.add(color)),
            );
            builder.spawn(pbr_bundle);
            spawn_wheels(builder, meshes, materials, builder.parent_entity());
        });
}

fn spawn_wheels(
    commands: &mut ChildBuilder,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<StandardMaterial>>,
    body: Entity,
) {
    let mesh: Mesh = Sphere::new(WHEEL_RADIUS).into();

    let front_rake = Vec3::new(0.0, -1.0, -0.9).normalize(); // about 30 degrees
    let front_wheel_pos = FRONT_ATTACH + (front_rake * REST_DISTANCE);

    wheel_caster(
        commands,
        FRONT_ATTACH,
        Dir3::new_unchecked(front_rake),
        body,
        REST_DISTANCE,
        CyberWheel::Front,
    );
    wheel_mesh(
        commands,
        &mut meshes,
        &mut materials,
        front_wheel_pos,
        mesh.clone(),
        WheelConfig::new(
            FRONT_ATTACH,
            REST_DISTANCE,
            SPRING_CONSTANT,
            DAMPING_CONSTANT,
            FRICTION_COEFF,
            WHEEL_RADIUS,
        ),
        CyberWheel::Front,
    );

    let rear_rake = Vec3::new(0.0, -1.0, 0.9).normalize();
    let rear_wheel_pos = REAR_ATTACH + (rear_rake * REST_DISTANCE);

    wheel_caster(
        commands,
        REAR_ATTACH,
        Dir3::new_unchecked(rear_rake),
        body,
        REST_DISTANCE,
        CyberWheel::Rear,
    );
    wheel_mesh(
        commands,
        &mut meshes,
        &mut materials,
        rear_wheel_pos,
        mesh,
        WheelConfig::new(
            REAR_ATTACH,
            REST_DISTANCE,
            SPRING_CONSTANT,
            DAMPING_CONSTANT,
            FRICTION_COEFF,
            WHEEL_RADIUS,
        ),
        CyberWheel::Rear,
    );
}

//-************************************************************************
// helper fns for the wheels
//-************************************************************************

fn wheel_caster(
    commands: &mut ChildBuilder,
    origin: Vec3,
    direction: Dir3,
    parent: Entity,
    rest_dist: Scalar,
    wheel: CyberWheel,
) {
    let caster = RayCaster::new(origin, direction)
        .with_max_distance(rest_dist)
        .with_max_hits(1)
        .with_query_filter(SpatialQueryFilter::from_excluded_entities([parent]));

    commands.spawn((caster, wheel));
}

fn wheel_mesh(
    commands: &mut ChildBuilder,
    meshes: &mut ResMut<Assets<Mesh>>,
    materials: &mut ResMut<Assets<StandardMaterial>>,
    position: Vec3,
    tire_mesh: Mesh,
    config: WheelConfig,
    wheel: CyberWheel,
) {
    let wheel_material = &StandardMaterial {
        base_color: Color::srgb(0.01, 0.01, 0.01),
        alpha_mode: AlphaMode::Opaque,
        perceptual_roughness: 0.5,
        ..Default::default()
    };

    let xform = Transform::from_translation(position);

    let name = match wheel {
        CyberWheel::Front => "front tire",
        CyberWheel::Rear => "rear tire",
    };

    commands.spawn((
        Name::new(name),
        config,
        Mesh3d(meshes.add(tire_mesh)),
        MeshMaterial3d(materials.add(wheel_material.clone())),
        xform,
        Collider::sphere(WHEEL_RADIUS),
        ColliderDensity(0.5),
        CollisionLayers::NONE,
        TransformInterpolation,
        wheel,
    ));
}

pub struct CyberBikePlugin;

impl Plugin for CyberBikePlugin {
    fn build(&self, app: &mut App) {
        app.register_type::<WheelConfig>();
        app.register_type::<WheelState>();
        app.add_systems(Startup, spawn_bike);
    }
}