actually kinda works, but needs simulated friction.

src/action/mod.rs

@@ -34,8 +34,7 @@ impl Plugin for CyberActionPlugin {
             .add_systems(
                 Update,
                 (
-                    reset_body_force,
-                    reset_wheel_forces,
+                    reset_external_forces,
                     cyber_lean,
                     falling_cat,
                     wheel_forces,

src/action/systems.rs

@@ -6,9 +6,12 @@ use bevy::{
     },
     render::color::Color,
 };
-use bevy_rapier3d::prelude::{
+use bevy_rapier3d::{
+    geometry::Friction,
+    prelude::{
         ExternalForce, QueryFilter, RapierConfiguration, RapierContext, ReadMassProperties,
         TimestepMode, Velocity,
+    },
 };
 
 #[cfg(feature = "inspector")]
@@ -34,29 +37,23 @@ pub(super) fn physics_init(
     config.gravity = Vec3::NEG_Y * settings.gravity;
 }
 
-pub(super) fn reset_body_force(
-    mut query: Query<&mut ExternalForce, With<CyberBikeBody>>,
+pub(super) fn reset_external_forces(
+    mut query: Query<&mut ExternalForce>,
     #[cfg(feature = "inspector")] mut debug_instant: ResMut<ActionDebugInstant>,
 ) {
-    let mut body_force = query.single_mut();
-
-    #[cfg(feature = "inspector")]
-    {
-        if debug_instant.elapsed().as_millis() > 1000 {
-            //dbg!(&body_force);
-            debug_instant.reset();
-        }
-    }
-
-    body_force.force = Vec3::ZERO;
-    body_force.torque = Vec3::ZERO;
-}
-
-pub(super) fn reset_wheel_forces(mut query: Query<&mut ExternalForce, With<CyberWheel>>) {
     for mut force in query.iter_mut() {
+        #[cfg(feature = "inspector")]
+        if debug_instant.elapsed().as_millis() > 1000 {
+            info!("{force:?}");
+        }
+
         force.force = Vec3::ZERO;
         force.torque = Vec3::ZERO;
     }
+    #[cfg(feature = "inspector")]
+    if debug_instant.elapsed().as_millis() > 1000 {
+        debug_instant.reset();
+    }
 }
 
 /// The desired lean angle, given steering input and speed.
@@ -135,6 +132,7 @@ pub(super) fn wheel_forces(
             &Transform,
             &Velocity,
             &mut ExternalForce,
+            &mut Friction,
             Option<&CyberSteering>,
         ),
         With<CyberWheel>,
@@ -149,32 +147,51 @@ pub(super) fn wheel_forces(
     let radius = wheel_config.radius;
 
     // inputs
-    let steering = input.yaw;
+    let yaw = input.yaw;
     let throttle = input.throttle * settings.accel;
 
-    for (xform, velocity, mut external_force, steering) in wheels_query.iter_mut() {
-        if let Some((_, projected)) =
-            context.project_point(xform.translation, false, QueryFilter::only_fixed())
-        {
-            let normal = (projected.point - xform.translation);
-            let len = normal.length();
-            if len < radius {
+    for (xform, velocity, mut external_force, mut friction, steering) in wheels_query.iter_mut() {
+        let pos = xform.translation;
+        if let Some((_, projected)) = context.project_point(pos, false, QueryFilter::only_fixed()) {
             let mut force = Vec3::ZERO;
+
+            gizmos.sphere(projected.point, Quat::IDENTITY, radius, Color::RED);
+
+            let dir = (projected.point - pos).normalize();
+
+            if let Some((_, intersection)) = context.cast_ray_and_get_normal(
+                pos,
+                dir,
+                radius * 1.05,
+                false,
+                QueryFilter::only_fixed(),
+            ) {
+                let norm = intersection.normal;
+                let point = intersection.point;
+
                 // do thrust's share
-                let thrust = normal.cross(xform.left().into()) * throttle;
+                let thrust = norm.cross(xform.right().into()) * throttle;
                 force += thrust;
 
                 // do steering's share
+                if steering.is_some() {
+                    let thrust = norm.cross(xform.back().into());
+                    force += yaw * thrust;
+                }
 
                 // do the friction's share
+                if input.brake {
+                    friction.coefficient = 2.0;
+                } else {
+                    friction.coefficient = 0.0;
+                }
 
                 // show the force
                 #[cfg(feature = "inspector")]
-                gizmos.arrow(xform.translation, force, Color::RED);
+                gizmos.arrow(pos, pos + force, Color::RED);
 
                 // ok apply the force
-                let ef = ExternalForce::at_point(force, projected.point, xform.translation);
-                *external_force = ef;
+                *external_force = ExternalForce::at_point(force, point, pos);
             }
         }
     }

src/bike/wheels.rs

@@ -83,14 +83,10 @@ pub(crate) fn spawn_wheels(
             .insert(not_sleeping)
             .id();
 
-        let axel_parent_entity = if let Some(steering) = steering {
+        let axel_parent_entity = if steering.is_some() {
             let neck_builder = FixedJointBuilder::new().local_anchor1(Vec3::new(0.0, 0.0, 0.1)); // this adds another 0.1m of trail
             let neck_joint = MultibodyJoint::new(fork_rb_entity, neck_builder);
-            let neck = commands
-                .spawn(RigidBody::Dynamic)
-                .insert(neck_joint)
-                .insert(steering)
-                .id();
+            let neck = commands.spawn(RigidBody::Dynamic).insert(neck_joint).id();
             neck
         } else {
             fork_rb_entity
@@ -99,9 +95,9 @@ pub(crate) fn spawn_wheels(
         let axel_builder = FixedJointBuilder::new();
         let axel_joint = MultibodyJoint::new(axel_parent_entity, axel_builder);
 
-        commands.spawn(pbr_bundle).insert((
+        let c = &mut commands.spawn(pbr_bundle);
+        c.insert((
             mass_props,
-            //wheel_damping,
             axel_joint,
             CyberWheel,
             not_sleeping,
@@ -119,6 +115,9 @@ pub(crate) fn spawn_wheels(
             wheels_collision_group,
             Collider::ball(conf.radius),
         ));
+        if steering.is_some() {
+            c.insert(CyberSteering);
+        }
     }
 }