cyber_rider/src/bike/wheels.rs

use avian3d::prelude::*;
use bevy::prelude::{Torus as Tire, *};

use super::{
    CyberFork, CyberSpring, CyberSteering, CyberWheel, Meshterial, WheelConfig,
    BIKE_WHEEL_COLLISION_GROUP,
};

pub fn spawn_wheels(
    commands: &mut Commands,
    bike: Entity,
    conf: &WheelConfig,
    meshterials: &mut Meshterial,
) {
    let (membership, filter) = BIKE_WHEEL_COLLISION_GROUP;
    let wheels_collision_group = CollisionLayers::new(membership, filter);
    let wheel_y = conf.y;
    let not_sleeping = SleepingDisabled;
    let ccd = SweptCcd::NON_LINEAR.include_dynamic(false);
    let limits = conf.limits;
    let (meshes, materials) = meshterials;
    let rake_vec: Vec3 = Vec3::new(0.0, 1.0, 0.57).normalize(); // about 30 degrees of rake

    let friction = Friction {
        dynamic_coefficient: conf.friction,
        static_coefficient: conf.friction,
        combine_rule: CoefficientCombine::Average,
    };

    let mut wheel_poses = Vec::with_capacity(2);

    // front
    {
        let wheel_x = 0.0;
        let wheel_z = -conf.front_forward;
        let offset = Vec3::new(wheel_x, wheel_y, wheel_z);
        wheel_poses.push((offset, Some(CyberSteering)));
    }

    // rear
    {
        let wheel_x = 0.0;
        let wheel_z = conf.rear_back;
        let offset = Vec3::new(wheel_x, wheel_y, wheel_z);
        wheel_poses.push((offset, None));
    }

    for (offset, steering) in wheel_poses {
        let (mesh, collider) = gen_tires(conf);

        let material = StandardMaterial {
            base_color: Color::linear_rgba(0.01, 0.01, 0.01, 1.0),
            alpha_mode: AlphaMode::Opaque,
            perceptual_roughness: 0.5,
            ..Default::default()
        };

        let pbr_bundle = PbrBundle {
            material: materials.add(material),
            mesh: meshes.add(mesh),
            ..Default::default()
        };

        let suspension_axis = if steering.is_some() {
            rake_vec
        } else {
            Vec3::Y
        };

        let wheel = commands
            .spawn(pbr_bundle)
            .insert((
                collider,
                ccd,
                not_sleeping,
                wheels_collision_group,
                friction,
                CyberWheel,
                ExternalForce::default(),
                Restitution::new(conf.restitution),
                SpatialBundle::default(),
                RigidBody::Dynamic,
                ColliderDensity(0.1),
                AngularVelocity::ZERO,
                ExternalTorque::ZERO,
            ))
            .id();

        let spring = CyberSpring(suspension_axis);
        let axel = if let Some(steering) = steering {
            commands.spawn((
                RigidBody::Dynamic,
                ExternalForce::ZERO,
                steering,
                spring,
                Collider::sphere(0.1),
                ColliderDensity(0.1),
            ))
        } else {
            commands.spawn((
                RigidBody::Dynamic,
                ExternalForce::ZERO,
                spring,
                Collider::sphere(0.1),
                ColliderDensity(0.1),
            ))
        }
        .insert(SpatialBundle::default())
        .id();
        let axel_joint = RevoluteJoint::new(axel, wheel).with_aligned_axis(Vec3::NEG_X);
        commands.spawn(axel_joint);

        // suspension and steering:
        if steering.is_some() {
            let joint = PrismaticJoint::new(axel, bike)
                .with_free_axis(suspension_axis)
                .with_local_anchor_1(Vec3::new(0.0, 0.0, 0.1))
                .with_local_anchor_2(offset)
                .with_limits(limits[0], limits[1]);
            commands.spawn((joint, CyberFork));
        } else {
            let joint = PrismaticJoint::new(axel, bike)
                .with_free_axis(suspension_axis)
                .with_local_anchor_2(offset)
                .with_limits(limits[0], limits[1]);
            commands.spawn(joint);
        };
    }
}

// do mesh shit
fn gen_tires(conf: &WheelConfig) -> (Mesh, Collider) {
    let wheel_rad = conf.radius;
    let tire_thickness = conf.thickness;
    let tire = Tire {
        minor_radius: tire_thickness,
        major_radius: wheel_rad,
    };

    let mut mesh = Mesh::from(tire);
    let tire_verts = mesh
        .attribute(Mesh::ATTRIBUTE_POSITION)
        .unwrap()
        .as_float3()
        .unwrap()
        .iter()
        .map(|v| {
            //
            let v = Vec3::from_array(*v);
            let m = Mat3::from_rotation_z(90.0f32.to_radians());
            let p = m.mul_vec3(v);
            p.to_array()
        })
        .collect::<Vec<[f32; 3]>>();
    mesh.remove_attribute(Mesh::ATTRIBUTE_POSITION);
    mesh.insert_attribute(Mesh::ATTRIBUTE_POSITION, tire_verts);

    let mut idxs = Vec::new();
    let indices = mesh.indices().unwrap().iter().collect::<Vec<_>>();
    for idx in indices.as_slice().chunks_exact(3) {
        idxs.push([idx[0] as u32, idx[1] as u32, idx[2] as u32]);
    }
    let wheel_collider = Collider::convex_decomposition_from_mesh(&mesh).unwrap();

    (mesh, wheel_collider)
}