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: QueryPipeline::cast_shape. This method has similar arguments as QueryPipeline::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

let shape = Cuboid::new(vector![1.0, 2.0]);
let shape_pos = Isometry::new(vector![0.0, 1.0], 0.8);
let shape_vel = vector![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((handle, hit)) = query_pipeline.cast_shape(rigid_body_set,
    collider_set, &shape_pos, &shape_vel, &shape, options, filter
) {
    // The first collider hit has the handle `handle`. The `hit` is a
    // structure containing details about the hit configuration.
    println!("Hit the collider {:?} with the configuration: {:?}", handle, hit);
}

Example 3D

let shape = Cuboid::new(vector![1.0, 2.0, 3.0]);
let shape_pos = Isometry::new(vector![0.0, 1.0, 0.0], vector![0.2, 0.7, 0.1]);
let shape_vel = vector![0.1, 0.4, 0.2];
let max_toi = 4.0;
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((handle, hit)) = query_pipeline.cast_shape(
    rigid_body_set, &collider_set, &shape_pos, &shape_vel, &shape, options, filter
) {
    // The first collider hit has the handle `handle`. The `hit` is a
    // structure containing details about the hit configuration.
    println!("Hit the collider {:?} with the configuration: {:?}", handle, 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.