scene_queries_shape_casting

Shape-casting (aka. sweep tests) is the big brother of ray-casting. The only difference with ray-cast is that instead of being a point travelling along a straight line, we have a complete shape travelling along a straight line. This is typically used for character controllers in games to determine by how much the player can move before it hits the environment.

info

Just like ray-casting, it is possible to control the behavior of the shape-casting like limiting the distance travelled by the shape cast, and ignoring some colliders. See the details about the max_toi and filter arguments in the ray-casting section.

There is only one shape-casting method: RapierContext::cast_shape. This method has similar arguments as RapierContext::cast_ray except that the ray is replaced by three arguments: the shape being cast, the initial position of the shape (this is analog to ray.origin) and the linear velocity the shape is travelling at (this is analog to ray.dir):

Example 2D

/* Cast a shape inside of a system. */
fn cast_shape(rapier_context: Res<RapierContext>) {
    let shape = Collider::cuboid(1.0, 2.0);
    let shape_pos = Vec2::new(1.0, 2.0);
    let shape_rot = 0.8;
    let shape_vel = Vec2::new(0.1, 0.4);
    let filter = QueryFilter::default();
    let options = ShapeCastOptions {
        max_time_of_impact: 4.0,
        target_distance: 0.0,
        stop_at_penetration: false,
        compute_impact_geometry_on_penetration: false,
    };

    if let Some((entity, hit)) =
        rapier_context.cast_shape(shape_pos, shape_rot, shape_vel, &shape, options, filter)
    {
        // The first collider hit has the entity `entity`. The `hit` is a
        // structure containing details about the hit configuration.
        println!(
            "Hit the entity {:?} with the configuration: {:?}",
            entity, hit
        );
    }
}

Example 3D

/* Cast a shape inside of a system. */
fn cast_shape(rapier_context: Res<RapierContext>) {
    let shape = Collider::cuboid(1.0, 2.0, 3.0);
    let shape_pos = Vec3::new(1.0, 2.0, 3.0);
    let shape_rot = Quat::from_rotation_z(0.8);
    let shape_vel = Vec3::new(0.1, 0.4, 0.2);
    let filter = QueryFilter::default();
    let options = ShapeCastOptions {
        max_time_of_impact: 4.0,
        target_distance: 0.0,
        stop_at_penetration: false,
        compute_impact_geometry_on_penetration: false,
    };

    if let Some((entity, hit)) =
        rapier_context.cast_shape(shape_pos, shape_rot, shape_vel, &shape, options, filter)
    {
        // The first collider hit has the entity `entity`. The `hit` is a
        // structure containing details about the hit configuration.
        println!(
            "Hit the entity {:?} with the configuration: {:?}",
            entity, hit
        );
    }
}

The result of the shape-casting includes the handle of the first collider being hit, as well as detailed information about the geometry of the hit:

• hit.toi: indicates the time of impact between the shape and the collider hit. This means that after travelling a distance of shape_vel * hit.toi the collider and the cast shape are exactly touching. If hit.toi == 0.0 then the shape is already intersecting a collider at its initial position.
• hit.witness1: indicates the contact point when the cast shape and the collider are touching, expressed in the local-space of the collider hit by the shape.
• hit.witness2: indicates the contact point when the cast shape and the collider are touching, expressed in the local-space of the cast shape.
• hit.normal1: indicates the normal at the contact point hit.witness1, expressed in the local-space of the collider hit by the shape.
• hit.normal2: indicates the normal at the contact point hit.witness2, expressed in the local-space of the cast shape.