Dedicated primitive example (#11697)

I just implemented this to record a video for the new blog post, but I
figured it would also make a good dedicated example. This also allows us
to remove a lot of code from the 2d/3d gizmo examples since it
supersedes this portion of code.

Depends on: #11699

Cargo.toml

@@ -2644,6 +2644,17 @@ description = "Demonstrates creating and using custom Ui materials"
 category = "UI (User Interface)"
 wasm = true
 
+[[example]]
+name = "render_primitives"
+path = "examples/math/render_primitives.rs"
+doc-scrape-examples = true
+
+[package.metadata.example.render_primitives]
+name = "Rendering Primitives"
+description = "Shows off rendering for all math primitives as both Meshes and Gizmos"
+category = "Math"
+wasm = true
+
 [profile.wasm-release]
 inherits = "release"
 opt-level = "z"

examples/2d/2d_gizmos.rs

@@ -6,74 +6,24 @@ use bevy::prelude::*;
 
 fn main() {
     App::new()
-        .init_state::<PrimitiveState>()
         .add_plugins(DefaultPlugins)
         .init_gizmo_group::<MyRoundGizmos>()
         .add_systems(Startup, setup)
         .add_systems(Update, (draw_example_collection, update_config))
-        .add_systems(Update, (draw_primitives, update_primitives))
         .run();
 }
 
 // We can create our own gizmo config group!
 #[derive(Default, Reflect, GizmoConfigGroup)]
 struct MyRoundGizmos {}
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, States, Default)]
-enum PrimitiveState {
-    #[default]
-    Nothing,
-    Circle,
-    Ellipse,
-    Capsule,
-    Line,
-    Plane,
-    Segment,
-    Triangle,
-    Rectangle,
-    RegularPolygon,
-}
-
-impl PrimitiveState {
-    const ALL: [Self; 10] = [
-        Self::Nothing,
-        Self::Circle,
-        Self::Ellipse,
-        Self::Capsule,
-        Self::Line,
-        Self::Plane,
-        Self::Segment,
-        Self::Triangle,
-        Self::Rectangle,
-        Self::RegularPolygon,
-    ];
-    fn next(self) -> Self {
-        Self::ALL
-            .into_iter()
-            .cycle()
-            .skip_while(|&x| x != self)
-            .nth(1)
-            .unwrap()
-    }
-    fn last(self) -> Self {
-        Self::ALL
-            .into_iter()
-            .rev()
-            .cycle()
-            .skip_while(|&x| x != self)
-            .nth(1)
-            .unwrap()
-    }
-}
-
 fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
     commands.spawn(Camera2dBundle::default());
     // text
     commands.spawn(TextBundle::from_section(
         "Hold 'Left' or 'Right' to change the line width of straight gizmos\n\
         Hold 'Up' or 'Down' to change the line width of round gizmos\n\
-        Press '1' or '2' to toggle the visibility of straight gizmos or round gizmos\n\
-        Press 'K' or 'J' to cycle through primitives rendered with gizmos",
+        Press '1' or '2' to toggle the visibility of straight gizmos or round gizmos",
         TextStyle {
             font: asset_server.load("fonts/FiraMono-Medium.ttf"),
             font_size: 24.,
@@ -130,92 +80,6 @@ fn draw_example_collection(
     );
 }
 
-fn draw_primitives(
-    mut gizmos: Gizmos,
-    time: Res<Time>,
-    primitive_state: Res<State<PrimitiveState>>,
-) {
-    let angle = time.elapsed_seconds();
-    let rotation = Mat2::from_angle(angle);
-    let position = rotation * Vec2::X;
-    let color = Color::WHITE;
-
-    const SIZE: f32 = 50.0;
-    match primitive_state.get() {
-        PrimitiveState::Nothing => {}
-        PrimitiveState::Circle => {
-            gizmos.primitive_2d(Circle { radius: SIZE }, position, angle, color);
-        }
-        PrimitiveState::Ellipse => gizmos.primitive_2d(
-            Ellipse {
-                half_size: Vec2::new(SIZE, SIZE * 0.5),
-            },
-            position,
-            angle,
-            color,
-        ),
-        PrimitiveState::Capsule => gizmos.primitive_2d(
-            Capsule2d {
-                radius: SIZE * 0.5,
-                half_length: SIZE,
-            },
-            position,
-            angle,
-            color,
-        ),
-        PrimitiveState::Line => drop(gizmos.primitive_2d(
-            Line2d {
-                direction: Direction2d::X,
-            },
-            position,
-            angle,
-            color,
-        )),
-        PrimitiveState::Plane => gizmos.primitive_2d(
-            Plane2d {
-                normal: Direction2d::Y,
-            },
-            position,
-            angle,
-            color,
-        ),
-        PrimitiveState::Segment => drop(gizmos.primitive_2d(
-            Segment2d {
-                direction: Direction2d::X,
-                half_length: SIZE * 0.5,
-            },
-            position,
-            angle,
-            color,
-        )),
-        PrimitiveState::Triangle => gizmos.primitive_2d(
-            Triangle2d {
-                vertices: [Vec2::ZERO, Vec2::Y, Vec2::X].map(|p| p * SIZE * 0.5),
-            },
-            position,
-            angle,
-            color,
-        ),
-        PrimitiveState::Rectangle => gizmos.primitive_2d(
-            Rectangle {
-                half_size: Vec2::splat(SIZE * 0.5),
-            },
-            position,
-            angle,
-            color,
-        ),
-        PrimitiveState::RegularPolygon => gizmos.primitive_2d(
-            RegularPolygon {
-                circumcircle: Circle { radius: SIZE * 0.5 },
-                sides: 5,
-            },
-            position,
-            angle,
-            color,
-        ),
-    }
-}
-
 fn update_config(
     mut config_store: ResMut<GizmoConfigStore>,
     keyboard: Res<ButtonInput<KeyCode>>,
@@ -247,16 +111,3 @@ fn update_config(
         my_config.enabled ^= true;
     }
 }
-
-fn update_primitives(
-    keyboard: Res<ButtonInput<KeyCode>>,
-    mut next_primitive_state: ResMut<NextState<PrimitiveState>>,
-    primitive_state: Res<State<PrimitiveState>>,
-) {
-    if keyboard.just_pressed(KeyCode::KeyJ) {
-        next_primitive_state.set(primitive_state.get().last());
-    }
-    if keyboard.just_pressed(KeyCode::KeyK) {
-        next_primitive_state.set(primitive_state.get().next());
-    }
-}