Add a bounding box gizmo (#8468)

# Objective

Add a bounding box gizmo

![Screenshot from 2023-04-22
23-49-40](https://user-images.githubusercontent.com/29694403/233808825-7593dc38-0623-48a9-b0d7-a4ca24a9e071.png)

## Changes
- Added the `AabbGizmo` component that will draw the `Aabb` component on
that entity.
- Added an option to draw all bounding boxes in a scene on the
`GizmoConfig` resource.
- Added `TransformPoint` trait to generalize over the point
transformation methods on various transform types (e.g `Transform` and
`GlobalTransform`).
- Changed the `Gizmos::cuboid` method to accept an `impl TransformPoint`
instead of separate translation, rotation, and scale.

crates/bevy_gizmos/Cargo.toml

@@ -21,3 +21,4 @@ bevy_utils = { path = "../bevy_utils", version = "0.11.0-dev" }
 bevy_core = { path = "../bevy_core", version = "0.11.0-dev" }
 bevy_reflect = { path = "../bevy_reflect", version = "0.11.0-dev" }
 bevy_core_pipeline = { path = "../bevy_core_pipeline", version = "0.11.0-dev" }
+bevy_transform = { path = "../bevy_transform", version = "0.11.0-dev" }

crates/bevy_gizmos/src/gizmos.rs

@@ -7,7 +7,8 @@ use bevy_ecs::{
     world::World,
 };
 use bevy_math::{Mat2, Quat, Vec2, Vec3};
-use bevy_render::prelude::Color;
+use bevy_render::color::Color;
+use bevy_transform::TransformPoint;
 
 type PositionItem = [f32; 3];
 type ColorItem = [f32; 4];
@@ -280,27 +281,31 @@ impl<'s> Gizmos<'s> {
     /// ```
     /// # use bevy_gizmos::prelude::*;
     /// # use bevy_render::prelude::*;
-    /// # use bevy_math::prelude::*;
+    /// # use bevy_transform::prelude::*;
     /// fn system(mut gizmos: Gizmos) {
-    ///     gizmos.cuboid(Vec3::ZERO, Quat::IDENTITY, Vec3::ONE, Color::GREEN);
+    ///     gizmos.cuboid(Transform::IDENTITY, Color::GREEN);
     /// }
     /// # bevy_ecs::system::assert_is_system(system);
     /// ```
     #[inline]
-    pub fn cuboid(&mut self, position: Vec3, rotation: Quat, size: Vec3, color: Color) {
-        let rect = rect_inner(size.truncate());
+    pub fn cuboid(&mut self, transform: impl TransformPoint, color: Color) {
+        let rect = rect_inner(Vec2::ONE);
         // Front
-        let [tlf, trf, brf, blf] = rect.map(|vec2| position + rotation * vec2.extend(size.z / 2.));
+        let [tlf, trf, brf, blf] = rect.map(|vec2| transform.transform_point(vec2.extend(0.5)));
         // Back
-        let [tlb, trb, brb, blb] = rect.map(|vec2| position + rotation * vec2.extend(-size.z / 2.));
+        let [tlb, trb, brb, blb] = rect.map(|vec2| transform.transform_point(vec2.extend(-0.5)));
 
-        let positions = [
-            tlf, trf, trf, brf, brf, blf, blf, tlf, // Front
-            tlb, trb, trb, brb, brb, blb, blb, tlb, // Back
-            tlf, tlb, trf, trb, brf, brb, blf, blb, // Front to back
+        let strip_positions = [
+            tlf, trf, brf, blf, tlf, // Front
+            tlb, trb, brb, blb, tlb, // Back
         ];
-        self.extend_list_positions(positions);
-        self.add_list_color(color, 24);
+        self.linestrip(strip_positions, color);
+
+        let list_positions = [
+            trf, trb, brf, brb, blf, blb, // Front to back
+        ];
+        self.extend_list_positions(list_positions);
+        self.add_list_color(color, 6);
     }
 
     /// Draw a line from `start` to `end`.

crates/bevy_gizmos/src/lib.rs

@@ -18,22 +18,31 @@
 
 use std::mem;
 
-use bevy_app::{Last, Plugin};
+use bevy_app::{Last, Plugin, Update};
 use bevy_asset::{load_internal_asset, Assets, Handle, HandleUntyped};
 use bevy_ecs::{
-    prelude::{Component, DetectChanges},
+    change_detection::DetectChanges,
+    component::Component,
+    entity::Entity,
+    query::Without,
+    reflect::ReflectComponent,
     schedule::IntoSystemConfigs,
-    system::{Commands, Res, ResMut, Resource},
+    system::{Commands, Query, Res, ResMut, Resource},
     world::{FromWorld, World},
 };
 use bevy_math::Mat4;
-use bevy_reflect::TypeUuid;
+use bevy_reflect::{
+    std_traits::ReflectDefault, FromReflect, Reflect, ReflectFromReflect, TypeUuid,
+};
 use bevy_render::{
+    color::Color,
     mesh::Mesh,
+    primitives::Aabb,
     render_phase::AddRenderCommand,
     render_resource::{PrimitiveTopology, Shader, SpecializedMeshPipelines},
     Extract, ExtractSchedule, Render, RenderApp, RenderSet,
 };
+use bevy_transform::components::{GlobalTransform, Transform};
 
 #[cfg(feature = "bevy_pbr")]
 use bevy_pbr::MeshUniform;
@@ -47,12 +56,12 @@ mod pipeline_2d;
 #[cfg(feature = "bevy_pbr")]
 mod pipeline_3d;
 
-use crate::gizmos::GizmoStorage;
+use gizmos::{GizmoStorage, Gizmos};
 
 /// The `bevy_gizmos` prelude.
 pub mod prelude {
     #[doc(hidden)]
-    pub use crate::{gizmos::Gizmos, GizmoConfig};
+    pub use crate::{gizmos::Gizmos, AabbGizmo, AabbGizmoConfig, GizmoConfig};
 }
 
 const LINE_SHADER_HANDLE: HandleUntyped =
@@ -68,7 +77,14 @@ impl Plugin for GizmoPlugin {
         app.init_resource::<MeshHandles>()
             .init_resource::<GizmoConfig>()
             .init_resource::<GizmoStorage>()
-            .add_systems(Last, update_gizmo_meshes);
+            .add_systems(Last, update_gizmo_meshes)
+            .add_systems(
+                Update,
+                (
+                    draw_aabbs,
+                    draw_all_aabbs.run_if(|config: Res<GizmoConfig>| config.aabb.draw_all),
+                ),
+            );
 
         let Ok(render_app) = app.get_sub_app_mut(RenderApp) else { return; };
 
@@ -101,7 +117,7 @@ impl Plugin for GizmoPlugin {
 }
 
 /// A [`Resource`] that stores configuration for gizmos.
-#[derive(Resource, Clone, Copy)]
+#[derive(Resource, Clone)]
 pub struct GizmoConfig {
     /// Set to `false` to stop drawing gizmos.
     ///
@@ -113,6 +129,8 @@ pub struct GizmoConfig {
     ///
     /// Defaults to `false`.
     pub on_top: bool,
+    /// Configuration for the [`AabbGizmo`].
+    pub aabb: AabbGizmoConfig,
 }
 
 impl Default for GizmoConfig {
@@ -120,10 +138,79 @@ impl Default for GizmoConfig {
         Self {
             enabled: true,
             on_top: false,
+            aabb: Default::default(),
         }
     }
 }
 
+/// Configuration for drawing the [`Aabb`] component on entities.
+#[derive(Clone, Default)]
+pub struct AabbGizmoConfig {
+    /// Draws all bounding boxes in the scene when set to `true`.
+    ///
+    /// To draw a specific entity's bounding box, you can add the [`AabbGizmo`] component.
+    ///
+    /// Defaults to `false`.
+    pub draw_all: bool,
+    /// The default color for bounding box gizmos.
+    ///
+    /// A random color is chosen per box if `None`.
+    ///
+    /// Defaults to `None`.
+    pub default_color: Option<Color>,
+}
+
+/// Add this [`Component`] to an entity to draw its [`Aabb`] component.
+#[derive(Component, Reflect, FromReflect, Default, Debug)]
+#[reflect(Component, FromReflect, Default)]
+pub struct AabbGizmo {
+    /// The color of the box.
+    ///
+    /// The default color from the [`GizmoConfig`] resource is used if `None`,
+    pub color: Option<Color>,
+}
+
+fn draw_aabbs(
+    query: Query<(Entity, &Aabb, &GlobalTransform, &AabbGizmo)>,
+    config: Res<GizmoConfig>,
+    mut gizmos: Gizmos,
+) {
+    for (entity, &aabb, &transform, gizmo) in &query {
+        let color = gizmo
+            .color
+            .or(config.aabb.default_color)
+            .unwrap_or_else(|| color_from_entity(entity));
+        gizmos.cuboid(aabb_transform(aabb, transform), color);
+    }
+}
+
+fn draw_all_aabbs(
+    query: Query<(Entity, &Aabb, &GlobalTransform), Without<AabbGizmo>>,
+    config: Res<GizmoConfig>,
+    mut gizmos: Gizmos,
+) {
+    for (entity, &aabb, &transform) in &query {
+        let color = config
+            .aabb
+            .default_color
+            .unwrap_or_else(|| color_from_entity(entity));
+        gizmos.cuboid(aabb_transform(aabb, transform), color);
+    }
+}
+
+fn color_from_entity(entity: Entity) -> Color {
+    let hue = entity.to_bits() as f32 * 100_000. % 360.;
+    Color::hsl(hue, 1., 0.5)
+}
+
+fn aabb_transform(aabb: Aabb, transform: GlobalTransform) -> GlobalTransform {
+    transform
+        * GlobalTransform::from(
+            Transform::from_translation(aabb.center.into())
+                .with_scale((aabb.half_extents * 2.).into()),
+        )
+}
+
 #[derive(Resource)]
 struct MeshHandles {
     list: Option<Handle<Mesh>>,
@@ -198,7 +285,7 @@ fn extract_gizmo_data(
     config: Extract<Res<GizmoConfig>>,
 ) {
     if config.is_changed() {
-        commands.insert_resource(**config);
+        commands.insert_resource(config.clone());
     }
 
     if !config.enabled {

crates/bevy_transform/src/lib.rs

@@ -14,12 +14,15 @@ pub mod prelude {
     #[doc(hidden)]
     pub use crate::{
         commands::BuildChildrenTransformExt, components::*, TransformBundle, TransformPlugin,
+        TransformPoint,
     };
 }
 
 use bevy_app::prelude::*;
 use bevy_ecs::prelude::*;
 use bevy_hierarchy::ValidParentCheckPlugin;
+use bevy_math::{Affine3A, Mat4, Vec3};
+
 use prelude::{GlobalTransform, Transform};
 use systems::{propagate_transforms, sync_simple_transforms};
 
@@ -131,3 +134,37 @@ impl Plugin for TransformPlugin {
             );
     }
 }
+
+/// A trait for point transformation methods.
+pub trait TransformPoint {
+    /// Transform a point.
+    fn transform_point(&self, point: impl Into<Vec3>) -> Vec3;
+}
+
+impl TransformPoint for Transform {
+    #[inline]
+    fn transform_point(&self, point: impl Into<Vec3>) -> Vec3 {
+        self.transform_point(point.into())
+    }
+}
+
+impl TransformPoint for GlobalTransform {
+    #[inline]
+    fn transform_point(&self, point: impl Into<Vec3>) -> Vec3 {
+        self.transform_point(point.into())
+    }
+}
+
+impl TransformPoint for Mat4 {
+    #[inline]
+    fn transform_point(&self, point: impl Into<Vec3>) -> Vec3 {
+        self.transform_point3(point.into())
+    }
+}
+
+impl TransformPoint for Affine3A {
+    #[inline]
+    fn transform_point(&self, point: impl Into<Vec3>) -> Vec3 {
+        self.transform_point3(point.into())
+    }
+}

examples/3d/3d_gizmos.rs

@@ -56,9 +56,7 @@ fn setup(
 
 fn system(mut gizmos: Gizmos, time: Res<Time>) {
     gizmos.cuboid(
-        Vec3::Y * -0.5,
-        Quat::IDENTITY,
-        Vec3::new(5., 1., 2.),
+        Transform::from_translation(Vec3::Y * -0.5).with_scale(Vec3::new(5., 1., 2.)),
         Color::BLACK,
     );
     gizmos.rect(

examples/tools/scene_viewer/scene_viewer_plugin.rs

@@ -3,7 +3,10 @@
 //! - Copy the code for the `SceneViewerPlugin` and add the plugin to your App.
 //! - Insert an initialized `SceneHandle` resource into your App's `AssetServer`.
 
-use bevy::{asset::LoadState, gltf::Gltf, prelude::*, scene::InstanceId};
+use bevy::{
+    asset::LoadState, gltf::Gltf, input::common_conditions::input_just_pressed, prelude::*,
+    scene::InstanceId,
+};
 
 use std::f32::consts::*;
 use std::fmt;
@@ -43,6 +46,7 @@ impl fmt::Display for SceneHandle {
 Scene Controls:
     L           - animate light direction
     U           - toggle shadows
+    B           - toggle bounding boxes
     C           - cycle through the camera controller and any cameras loaded from the scene
 
     Space       - Play/Pause animation
@@ -63,6 +67,7 @@ impl Plugin for SceneViewerPlugin {
                 (
                     update_lights,
                     camera_tracker,
+                    toggle_bounding_boxes.run_if(input_just_pressed(KeyCode::B)),
                     #[cfg(feature = "animation")]
                     (start_animation, keyboard_animation_control),
                 ),
@@ -70,6 +75,10 @@ impl Plugin for SceneViewerPlugin {
     }
 }
 
+fn toggle_bounding_boxes(mut config: ResMut<GizmoConfig>) {
+    config.aabb.draw_all ^= true;
+}
+
 fn scene_load_check(
     asset_server: Res<AssetServer>,
     mut scenes: ResMut<Assets<Scene>>,