avian_pickup 0.1.3

A plugin for implementing picking up dynamic rigid bodies in Avian physics for the Bevy engine.Modeled after Half Life 2's gravity gun.
Documentation 
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use super::Prop;
use crate::prelude::*;

/// Inspired by [`CWeaponPhysCannon::FindObjectTrace`](https://github.com/ValveSoftware/source-sdk-2013/blob/master/mp/src/game/server/hl2/weapon_physcannon.cpp#L2470)
pub(super) fn find_prop_in_trace(
    spatial_query: &SpatialQuery,
    origin: Transform,
    config: &AvianPickupActor,
    q_rigid_body: &Query<&RigidBody>,
    q_collider_parent: &Query<&ColliderParent>,
) -> Option<Prop> {
    // Fun fact: Valve lies to you and actually multiplies this by 4 at this point.
    let test_length = config.interaction_distance;
    let is_dynamic = |entity: Entity| {
        let Ok(collider_parent) = q_collider_parent.get(entity) else {
            return false;
        };
        let rigid_body = collider_parent.get();
        q_rigid_body
            .get(rigid_body)
            .is_ok_and(|rigid_body| rigid_body.is_dynamic())
    };
    let hit = spatial_query
        .cast_ray_predicate(
            origin.translation,
            origin.forward(),
            test_length,
            true,
            &config.prop_filter,
            &is_dynamic,
        )
        .and_then(|hit| {
            q_collider_parent
                .get(hit.entity)
                .ok()
                .map(|parent| (parent.get(), hit.distance))
        })
        .filter(|(rigid_body, distance)| {
            if let Some(terrain_hit) = spatial_query.cast_ray(
                origin.translation,
                origin.forward(),
                *distance,
                true,
                &config.obstacle_filter,
            ) {
                let terrain_rigid_body = q_collider_parent
                    .get(terrain_hit.entity)
                    .map_or(terrain_hit.entity, |collider_parent| collider_parent.get());
                terrain_rigid_body == *rigid_body
            } else {
                true
            }
        });

    if let Some((rigid_body, distance)) = hit {
        Prop {
            entity: rigid_body,
            toi: distance,
        }
        .into()
    } else {
        // This has a half-extent of 4 inches in the 2013 code, which is about 1 cm
        const MAGIC_HALF_EXTENT_ASK_VALVE: f32 = 0.01;
        let fake_aabb_because_parry_cannot_do_aabb_casts =
            Cuboid::from_size(Vec3::splat(2. * MAGIC_HALF_EXTENT_ASK_VALVE)).into();
        let hit = spatial_query.cast_shape_predicate(
            &fake_aabb_because_parry_cannot_do_aabb_casts,
            origin.translation,
            origin.rotation,
            origin.forward(),
            &ShapeCastConfig::from_max_distance(test_length),
            &config.prop_filter,
            &is_dynamic,
        );
        hit.filter(|hit| {
            if let Some(terrain_hit) = spatial_query.cast_shape(
                &fake_aabb_because_parry_cannot_do_aabb_casts,
                origin.translation,
                origin.rotation,
                origin.forward(),
                &ShapeCastConfig::from_max_distance(hit.distance),
                &config.obstacle_filter,
            ) {
                terrain_hit.entity == hit.entity
            } else {
                true
            }
        })
        .map(|hit| Prop {
            entity: hit.entity,
            toi: hit.distance,
        })
    }
}