Consistently use PI to specify angles in examples. (bevyengine#5825)

Examples inconsistently use either `TAU`, `PI`, `FRAC_PI_2` or `FRAC_PI_4`.
Often in odd ways and without `use`ing the constants, making it difficult to parse.

 * Use `PI` to specify angles.
 * General code-quality improvements.
 * Fix borked `hierarchy` example.


Co-authored-by: devil-ira <justthecooldude@gmail.com>

examples/2d/mesh2d_manual.rs

@@ -3,6 +3,8 @@
 //! It doesn't use the [`Material2d`] abstraction, but changes the vertex buffer to include vertex color.
 //! Check out the "mesh2d" example for simpler / higher level 2d meshes.
 
+use std::f32::consts::PI;
+
 use bevy::{
     core_pipeline::core_2d::Transparent2d,
     prelude::*,
@@ -62,12 +64,12 @@ fn star(
     // These vertices are specified in 3D space.
     let mut v_pos = vec![[0.0, 0.0, 0.0]];
     for i in 0..10 {
-        // Angle of each vertex is 1/10 of TAU, plus PI/2 for positioning vertex 0
-        let a = std::f32::consts::FRAC_PI_2 - i as f32 * std::f32::consts::TAU / 10.0;
-        // Radius of internal vertices (2, 4, 6, 8, 10) is 100, it's 200 for external
+        // The angle between each vertex is 1/10 of a full rotation.
+        let a = i as f32 * PI / 5.0;
+        // The radius of inner vertices (even indices) is 100. For outer vertices (odd indices) it's 200.
         let r = (1 - i % 2) as f32 * 100.0 + 100.0;
-        // Add the vertex coordinates
-        v_pos.push([r * a.cos(), r * a.sin(), 0.0]);
+        // Add the vertex position.
+        v_pos.push([r * a.sin(), r * a.cos(), 0.0]);
     }
     // Set the position attribute
     star.insert_attribute(Mesh::ATTRIBUTE_POSITION, v_pos);

examples/3d/lighting.rs

@@ -1,6 +1,8 @@
 //! Illustrates different lights of various types and colors, some static, some moving over
 //! a simple scene.
 
+use std::f32::consts::PI;
+
 use bevy::prelude::*;
 
 fn main() {
@@ -34,7 +36,7 @@ fn setup(
 
     // left wall
     let mut transform = Transform::from_xyz(2.5, 2.5, 0.0);
-    transform.rotate_z(std::f32::consts::FRAC_PI_2);
+    transform.rotate_z(PI / 2.);
     commands.spawn_bundle(PbrBundle {
         mesh: meshes.add(Mesh::from(shape::Box::new(5.0, 0.15, 5.0))),
         transform,
@@ -47,7 +49,7 @@ fn setup(
     });
     // back (right) wall
     let mut transform = Transform::from_xyz(0.0, 2.5, -2.5);
-    transform.rotate_x(std::f32::consts::FRAC_PI_2);
+    transform.rotate_x(PI / 2.);
     commands.spawn_bundle(PbrBundle {
         mesh: meshes.add(Mesh::from(shape::Box::new(5.0, 0.15, 5.0))),
         transform,
@@ -138,9 +140,7 @@ fn setup(
         })
         .with_children(|builder| {
             builder.spawn_bundle(PbrBundle {
-                transform: Transform::from_rotation(Quat::from_rotation_x(
-                    std::f32::consts::PI / 2.0,
-                )),
+                transform: Transform::from_rotation(Quat::from_rotation_x(PI / 2.0)),
                 mesh: meshes.add(Mesh::from(shape::Capsule {
                     depth: 0.125,
                     radius: 0.1,
@@ -202,7 +202,7 @@ fn setup(
         },
         transform: Transform {
             translation: Vec3::new(0.0, 2.0, 0.0),
-            rotation: Quat::from_rotation_x(-std::f32::consts::FRAC_PI_4),
+            rotation: Quat::from_rotation_x(-PI / 4.),
             ..default()
         },
         ..default()

examples/3d/load_gltf.rs

@@ -1,5 +1,7 @@
 //! Loads and renders a glTF file as a scene.
 
+use std::f32::consts::PI;
+
 use bevy::prelude::*;
 
 fn main() {
@@ -50,8 +52,8 @@ fn animate_light_direction(
         transform.rotation = Quat::from_euler(
             EulerRot::ZYX,
             0.0,
-            time.seconds_since_startup() as f32 * std::f32::consts::TAU / 10.0,
-            -std::f32::consts::FRAC_PI_4,
+            time.seconds_since_startup() as f32 * PI / 5.0,
+            -PI / 4.,
         );
     }
 }

examples/3d/render_to_texture.rs

@@ -1,5 +1,7 @@
 //! Shows how to render to a texture. Useful for mirrors, UI, or exporting images.
 
+use std::f32::consts::PI;
+
 use bevy::{
     core_pipeline::clear_color::ClearColorConfig,
     prelude::*,
@@ -104,7 +106,7 @@ fn setup(
                 ..default()
             },
             transform: Transform::from_translation(Vec3::new(0.0, 0.0, 15.0))
-                .looking_at(Vec3::default(), Vec3::Y),
+                .looking_at(Vec3::ZERO, Vec3::Y),
             ..default()
         })
         .insert(first_pass_layer);
@@ -125,19 +127,15 @@ fn setup(
         .spawn_bundle(PbrBundle {
             mesh: cube_handle,
             material: material_handle,
-            transform: Transform {
-                translation: Vec3::new(0.0, 0.0, 1.5),
-                rotation: Quat::from_rotation_x(-std::f32::consts::PI / 5.0),
-                ..default()
-            },
+            transform: Transform::from_xyz(0.0, 0.0, 1.5)
+                .with_rotation(Quat::from_rotation_x(-PI / 5.0)),
             ..default()
         })
         .insert(MainPassCube);
 
     // The main pass camera.
     commands.spawn_bundle(Camera3dBundle {
-        transform: Transform::from_translation(Vec3::new(0.0, 0.0, 15.0))
-            .looking_at(Vec3::default(), Vec3::Y),
+        transform: Transform::from_xyz(0.0, 0.0, 15.0).looking_at(Vec3::ZERO, Vec3::Y),
         ..default()
     });
 }

examples/3d/shadow_biases.rs

@@ -1,5 +1,7 @@
 //! Demonstrates how shadow biases affect shadows in a 3d scene.
 
+use std::f32::consts::PI;
+
 use bevy::{input::mouse::MouseMotion, prelude::*};
 
 fn main() {
@@ -61,8 +63,6 @@ fn setup(
         ..default()
     });
 
-    let theta = std::f32::consts::FRAC_PI_4;
-    let light_transform = Mat4::from_euler(EulerRot::ZYX, 0.0, std::f32::consts::FRAC_PI_2, -theta);
     commands.spawn_bundle(DirectionalLightBundle {
         directional_light: DirectionalLight {
             illuminance: 100000.0,
@@ -80,7 +80,12 @@ fn setup(
             shadows_enabled: true,
             ..default()
         },
-        transform: Transform::from_matrix(light_transform),
+        transform: Transform::from_rotation(Quat::from_euler(
+            EulerRot::ZYX,
+            0.0,
+            PI / 2.,
+            -PI / 4.,
+        )),
         ..default()
     });
 
@@ -308,16 +313,10 @@ fn camera_controller(
 
         if mouse_delta != Vec2::ZERO {
             // Apply look update
-            let (pitch, yaw) = (
-                (options.pitch - mouse_delta.y * 0.5 * options.sensitivity * dt).clamp(
-                    -0.99 * std::f32::consts::FRAC_PI_2,
-                    0.99 * std::f32::consts::FRAC_PI_2,
-                ),
-                options.yaw - mouse_delta.x * options.sensitivity * dt,
-            );
-            transform.rotation = Quat::from_euler(EulerRot::ZYX, 0.0, yaw, pitch);
-            options.pitch = pitch;
-            options.yaw = yaw;
+            options.pitch = (options.pitch - mouse_delta.y * 0.5 * options.sensitivity * dt)
+                .clamp(-PI / 2., PI / 2.);
+            options.yaw -= mouse_delta.x * options.sensitivity * dt;
+            transform.rotation = Quat::from_euler(EulerRot::ZYX, 0.0, options.yaw, options.pitch);
         }
     }
 }

examples/3d/shadow_caster_receiver.rs

@@ -1,5 +1,7 @@
 //! Demonstrates how to prevent meshes from casting/receiving shadows in a 3d scene.
 
+use std::f32::consts::PI;
+
 use bevy::{
     pbr::{NotShadowCaster, NotShadowReceiver},
     prelude::*,
@@ -89,8 +91,6 @@ fn setup(
         ..default()
     });
 
-    let theta = std::f32::consts::FRAC_PI_4;
-    let light_transform = Mat4::from_euler(EulerRot::ZYX, 0.0, std::f32::consts::FRAC_PI_2, -theta);
     commands.spawn_bundle(DirectionalLightBundle {
         directional_light: DirectionalLight {
             illuminance: 100000.0,
@@ -106,7 +106,12 @@ fn setup(
             shadows_enabled: true,
             ..default()
         },
-        transform: Transform::from_matrix(light_transform),
+        transform: Transform::from_rotation(Quat::from_euler(
+            EulerRot::ZYX,
+            0.0,
+            PI / 2.,
+            -PI / 4.,
+        )),
         ..default()
     });
 

examples/3d/shapes.rs

@@ -1,6 +1,8 @@
 //! This example demonstrates the built-in 3d shapes in Bevy.
 //! The scene includes a patterned texture and a rotation for visualizing the normals and UVs.
 
+use std::f32::consts::PI;
+
 use bevy::{
     prelude::*,
     render::render_resource::{Extent3d, TextureDimension, TextureFormat},
@@ -48,15 +50,12 @@ fn setup(
             .spawn_bundle(PbrBundle {
                 mesh: shape,
                 material: debug_material.clone(),
-                transform: Transform {
-                    translation: Vec3::new(
-                        -X_EXTENT / 2. + i as f32 / (num_shapes - 1) as f32 * X_EXTENT,
-                        2.0,
-                        0.0,
-                    ),
-                    rotation: Quat::from_rotation_x(-std::f32::consts::PI / 4.),
-                    ..default()
-                },
+                transform: Transform::from_xyz(
+                    -X_EXTENT / 2. + i as f32 / (num_shapes - 1) as f32 * X_EXTENT,
+                    2.0,
+                    0.0,
+                )
+                .with_rotation(Quat::from_rotation_x(-PI / 4.)),
                 ..default()
             })
             .insert(Shape);

examples/3d/skybox.rs

@@ -1,5 +1,7 @@
 //! Load a cubemap texture onto a cube like a skybox and cycle through different compressed texture formats
 
+use std::f32::consts::PI;
+
 use bevy::{
     asset::LoadState,
     input::mouse::MouseMotion,
@@ -66,19 +68,16 @@ fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
             illuminance: 32000.0,
             ..default()
         },
-        transform: Transform {
-            translation: Vec3::new(0.0, 2.0, 0.0),
-            rotation: Quat::from_rotation_x(-std::f32::consts::FRAC_PI_4),
-            ..default()
-        },
+        transform: Transform::from_xyz(0.0, 2.0, 0.0)
+            .with_rotation(Quat::from_rotation_x(-PI / 4.)),
         ..default()
     });
 
     let skybox_handle = asset_server.load(CUBEMAPS[0].0);
     // camera
     commands
         .spawn_bundle(Camera3dBundle {
-            transform: Transform::from_xyz(0.0, 0.0, 8.0).looking_at(Vec3::default(), Vec3::Y),
+            transform: Transform::from_xyz(0.0, 0.0, 8.0).looking_at(Vec3::ZERO, Vec3::Y),
             ..default()
         })
         .insert(CameraController::default());
@@ -410,16 +409,10 @@ pub fn camera_controller(
 
         if mouse_delta != Vec2::ZERO {
             // Apply look update
-            let (pitch, yaw) = (
-                (options.pitch - mouse_delta.y * 0.5 * options.sensitivity * dt).clamp(
-                    -0.99 * std::f32::consts::FRAC_PI_2,
-                    0.99 * std::f32::consts::FRAC_PI_2,
-                ),
-                options.yaw - mouse_delta.x * options.sensitivity * dt,
-            );
-            transform.rotation = Quat::from_euler(EulerRot::ZYX, 0.0, yaw, pitch);
-            options.pitch = pitch;
-            options.yaw = yaw;
+            options.pitch = (options.pitch - mouse_delta.y * 0.5 * options.sensitivity * dt)
+                .clamp(-PI / 2., PI / 2.);
+            options.yaw -= mouse_delta.x * options.sensitivity * dt;
+            transform.rotation = Quat::from_euler(EulerRot::ZYX, 0.0, options.yaw, options.pitch);
         }
     }
 }

examples/3d/split_screen.rs

@@ -1,5 +1,7 @@
 //! Renders two cameras to the same window to accomplish "split screen".
 
+use std::f32::consts::PI;
+
 use bevy::{
     core_pipeline::clear_color::ClearColorConfig,
     prelude::*,
@@ -36,12 +38,7 @@ fn setup(
 
     // Light
     commands.spawn_bundle(DirectionalLightBundle {
-        transform: Transform::from_rotation(Quat::from_euler(
-            EulerRot::ZYX,
-            0.0,
-            1.0,
-            -std::f32::consts::FRAC_PI_4,
-        )),
+        transform: Transform::from_rotation(Quat::from_euler(EulerRot::ZYX, 0.0, 1.0, -PI / 4.)),
         directional_light: DirectionalLight {
             shadows_enabled: true,
             ..default()

examples/3d/spotlight.rs

@@ -1,3 +1,5 @@
+use std::f32::consts::PI;
+
 use bevy::{
     diagnostic::{FrameTimeDiagnosticsPlugin, LogDiagnosticsPlugin},
     pbr::NotShadowCaster,
@@ -74,8 +76,8 @@ fn setup(
                         intensity: 200.0, // lumens
                         color: Color::WHITE,
                         shadows_enabled: true,
-                        inner_angle: std::f32::consts::PI / 4.0 * 0.85,
-                        outer_angle: std::f32::consts::PI / 4.0,
+                        inner_angle: PI / 4.0 * 0.85,
+                        outer_angle: PI / 4.0,
                         ..default()
                     },
                     ..default()
@@ -123,13 +125,11 @@ fn light_sway(time: Res<Time>, mut query: Query<(&mut Transform, &mut SpotLight)
     for (mut transform, mut angles) in query.iter_mut() {
         transform.rotation = Quat::from_euler(
             EulerRot::XYZ,
-            -std::f32::consts::FRAC_PI_2
-                + (time.seconds_since_startup() * 0.67 * 3.0).sin() as f32 * 0.5,
+            -PI / 2. + (time.seconds_since_startup() * 0.67 * 3.0).sin() as f32 * 0.5,
             (time.seconds_since_startup() * 3.0).sin() as f32 * 0.5,
             0.0,
         );
-        let angle = ((time.seconds_since_startup() * 1.2).sin() as f32 + 1.0)
-            * (std::f32::consts::FRAC_PI_4 - 0.1);
+        let angle = ((time.seconds_since_startup() * 1.2).sin() as f32 + 1.0) * (PI / 4. - 0.1);
         angles.inner_angle = angle * 0.8;
         angles.outer_angle = angle;
     }
@@ -140,7 +140,7 @@ fn movement(
     time: Res<Time>,
     mut query: Query<&mut Transform, With<Movable>>,
 ) {
-    for mut transform in query.iter_mut() {
+    for mut transform in &mut query {
         let mut direction = Vec3::ZERO;
         if input.pressed(KeyCode::Up) {
             direction.z -= 1.0;