refactor player component and entity hierarchy, and add some document…

…ation

src/main.rs

@@ -26,57 +26,90 @@ fn setup(
     mut meshes: ResMut<Assets<Mesh>>,
     mut materials: ResMut<Assets<StandardMaterial>>,
 ) {
-    cmds.spawn((
+    /*
+    Lowercase denotes an entity, and uppercase denotes a component:
+
+    player
+    ├── Player
+    ├── TransformBundle
+    ├── VisibilityBundle
+    ├── body
+    │   └── BodyBundle
+    └── head
+        ├── Head (marker)
+        ├── TransformBundle (offsets the head from the player)
+        ├── VisibilityBundle (camera needs to be child of a visible entity)
+        └── camera
+            ├── AtmosphereCamera (cancels atmosphere translation)
+            ├── Camera3dBundle
+            ├── CameraMode (first or third person)
+            ├── Fxaa
+            └── TransformBundle (moves camera w.r.t. head orientation)
+    */
+
+    let visibility_bundle = || VisibilityBundle {
+        visibility: Visibility::Visible,
+        ..default()
+    };
+
+    let player_bundle = (
         player::Player,
-        VisibilityBundle {
-            visibility: Visibility::Visible,
-            ..default()
-        },
+        visibility_bundle(),
         TransformBundle {
             local: Transform::from_xyz(2.0, 170.0, 2.0).looking_to(Vec3::Z, Vec3::Y),
             ..default()
         },
-    ))
-    .with_children(|player| {
-        player.spawn(player::Body).insert(MaterialMeshBundle {
+    );
+
+    let body_bundle = player::BodyBundle {
+        material_mesh_bundle: MaterialMeshBundle {
             mesh: meshes.add(Mesh::from(shape::Box::new(0.5, 1.8, 0.5))),
             material: materials.add(StandardMaterial {
                 base_color: Color::WHITE,
                 ..default()
             }),
             transform: Transform::IDENTITY.looking_to(Vec3::Z, Vec3::Y),
             ..default()
-        });
+        },
+        ..default()
+    };
 
-        player
-            .spawn((
-                player::Head,
-                TransformBundle {
-                    // head is 1.8m above feet
-                    local: Transform::from_translation(Vec3::new(0.0, 0.9, 0.0))
-                        .looking_to(Vec3::Z, Vec3::Y),
-                    ..default()
-                },
-            ))
-            .with_children(|head| {
-                // spawn camera as a child of head
-                head.spawn(Camera3dBundle {
-                    projection: bevy::render::camera::Projection::Perspective(
-                        PerspectiveProjection {
-                            fov: PI / 2.,
-                            far: 2048.0,
-                            ..Default::default()
-                        },
-                    ),
-                    transform: Transform::from_translation(Vec3::new(0.0, 0.0, -5.0))
-                        .looking_to(Vec3::Z, Vec3::Y),
-                    ..Default::default()
-                })
-                .insert(CameraMode::ThirdPersonForward);
-            });
-    })
-    .insert(Fxaa::default())
-    .insert(bevy_atmosphere::plugin::AtmosphereCamera::default());
+    let head_bundle = (
+        player::Head,
+        visibility_bundle(),
+        TransformBundle {
+            // head is 1.8m above feet or 0.9m above the center
+            local: Transform::from_translation(Vec3::new(0.0, 0.9, 0.0))
+                .looking_to(Vec3::Z, Vec3::Y),
+            ..default()
+        },
+    );
+
+    let camera_bundle = (
+        CameraMode::ThirdPersonForward,
+        visibility_bundle(),
+        Camera3dBundle {
+            projection: bevy::render::camera::Projection::Perspective(PerspectiveProjection {
+                fov: PI / 2.,
+                far: 2048.0,
+                ..Default::default()
+            }),
+            transform: Transform::from_translation(Vec3::new(0.0, 0.0, -5.0))
+                .looking_to(Vec3::Z, Vec3::Y),
+            ..default()
+        },
+        Fxaa::default(),
+        bevy_atmosphere::plugin::AtmosphereCamera::default(),
+    );
+
+    cmds.spawn(player_bundle).with_children(|player| {
+        player.spawn(body_bundle);
+
+        player.spawn(head_bundle).with_children(|head| {
+            // spawn camera as a child of head
+            head.spawn(camera_bundle);
+        });
+    });
 
     cmds.insert_resource(AmbientLight {
         color: Color::WHITE,

src/voxel/world/chunks.rs

@@ -1,20 +1,26 @@
 use bevy::{
     math::IVec3,
     prelude::{
-        Changed, Commands, CoreSet, Entity, GlobalTransform, IntoSystemConfig, IntoSystemConfigs,
-        IntoSystemSetConfig, Plugin, Query, Res, ResMut, Resource, SystemSet, With,
+        Changed, Commands, Component, CoreSet, Entity, GlobalTransform, IntoSystemConfig,
+        IntoSystemConfigs, IntoSystemSetConfig, Plugin, Query, Res, ResMut, Resource, SystemSet,
+        With,
     },
     utils::{HashMap, HashSet},
 };
 use float_ord::FloatOrd;
 
-use super::{player, Chunk, ChunkShape, CHUNK_LENGTH};
+use super::{Chunk, ChunkShape, CHUNK_LENGTH};
 use crate::voxel::storage::ChunkMap;
 use crate::voxel::Voxel;
 
+// @todo: should this contain a radius so that different entities could cause chunk loading in different ranges?
+#[derive(Component, Default)]
+/// Marker component for entities with a [GlobalTransform] which are tracked for the purpose of loading terrain.
+pub struct LoadChunksAround;
+
 /// Updates the current chunk position for the current player.
 fn update_player_pos(
-    player: Query<&GlobalTransform, (With<player::Body>, Changed<GlobalTransform>)>,
+    player: Query<&GlobalTransform, (With<LoadChunksAround>, Changed<GlobalTransform>)>,
     mut chunk_pos: ResMut<CurrentLocalPlayerChunk>,
 ) {
     if let Ok(ply) = player.get_single() {

src/voxel/world/player.rs

@@ -4,13 +4,24 @@ use std::f32::consts::FRAC_PI_2;
 
 use crate::debug::DebugUISet;
 
+use super::chunks::LoadChunksAround;
+
 const BODY_ROTATION_SLERP: f32 = 0.5;
 
 #[derive(Component)]
 pub struct Player;
 
+#[derive(Bundle, Default)]
+pub struct BodyBundle<M: Material> {
+    pub material_mesh_bundle: MaterialMeshBundle<M>,
+
+    // defaults are fine for these:
+    pub body: Body,
+    pub load_chunks_around: LoadChunksAround,
+}
+
 /// Marker component for player body.
-#[derive(Component)]
+#[derive(Component, Default)]
 pub struct Body;
 
 #[derive(Component)]