[Merged by Bors] - Add RegularPolygon and Circle meshes

Cargo.toml

@@ -140,8 +140,8 @@ name = "mesh2d_manual"
 path = "examples/2d/mesh2d_manual.rs"
 
 [[example]]
-name = "rect"
-path = "examples/2d/rect.rs"
+name = "shapes"
+path = "examples/2d/shapes.rs"
 
 [[example]]
 name = "sprite"

crates/bevy_render/src/mesh/shape/mod.rs

@@ -224,11 +224,13 @@ impl From<Plane> for Mesh {
 
 mod capsule;
 mod icosphere;
+mod regular_polygon;
 mod torus;
 mod uvsphere;
 
 pub use capsule::{Capsule, CapsuleUvProfile};
 pub use icosphere::Icosphere;
+pub use regular_polygon::{Circle, RegularPolygon};
 pub use torus::Torus;
 pub use uvsphere::UVSphere;
 use wgpu::PrimitiveTopology;

crates/bevy_render/src/mesh/shape/regular_polygon.rs

@@ -0,0 +1,103 @@
+use crate::mesh::{Indices, Mesh};
+use wgpu::PrimitiveTopology;
+
+/// A regular polygon in the xy plane
+#[derive(Debug, Copy, Clone)]
+pub struct RegularPolygon {
+    /// Inscribed radius in the xy plane.
+    pub radius: f32,
+    /// Number of sides.
+    pub sides: usize,
+}
+
+impl Default for RegularPolygon {
+    fn default() -> Self {
+        Self {
+            radius: 0.5,
+            sides: 6,
+        }
+    }
+}
+
+impl RegularPolygon {
+    /// Creates a regular polygon in the xy plane
+    pub fn new(radius: f32, sides: usize) -> Self {
+        Self { radius, sides }
+    }
+}
+
+impl From<RegularPolygon> for Mesh {
+    fn from(polygon: RegularPolygon) -> Self {
+        let RegularPolygon { radius, sides } = polygon;
+
+        debug_assert!(sides > 2, "RegularPolygon requires at least 3 sides.");
+
+        let mut positions = Vec::with_capacity(sides);
+        let mut normals = Vec::with_capacity(sides);
+        let mut uvs = Vec::with_capacity(sides);
+
+        let step = std::f32::consts::TAU / sides as f32;
+        for i in 0..sides {
+            let theta = std::f32::consts::FRAC_PI_2 - i as f32 * step;
+            let (sin, cos) = theta.sin_cos();
+
+            positions.push([cos * radius, sin * radius, 0.0]);
+            normals.push([0.0, 0.0, 1.0]);
+            uvs.push([0.5 * (cos + 1.0), 1.0 - 0.5 * (sin + 1.0)]);
+        }
+
+        let mut indices = Vec::with_capacity((sides - 2) * 3);
+        for i in 1..(sides as u32 - 1) {
+            indices.extend_from_slice(&[0, i + 1, i]);
+        }
+
+        let mut mesh = Mesh::new(PrimitiveTopology::TriangleList);
+        mesh.insert_attribute(Mesh::ATTRIBUTE_POSITION, positions);
+        mesh.insert_attribute(Mesh::ATTRIBUTE_NORMAL, normals);
+        mesh.insert_attribute(Mesh::ATTRIBUTE_UV_0, uvs);
+        mesh.set_indices(Some(Indices::U32(indices)));
+        mesh
+    }
+}
+
+/// A circle in the xy plane
+pub struct Circle {
+    /// Inscribed radius in the xy plane.
+    pub radius: f32,
+    /// The number of vertices used.
+    pub vertices: usize,
+}
+
+impl Default for Circle {
+    fn default() -> Self {
+        Self {
+            radius: 0.5,
+            vertices: 64,
+        }
+    }
+}
+
+impl Circle {
+    /// Creates a circle in the xy plane
+    pub fn new(radius: f32) -> Self {
+        Self {
+            radius,
+            ..Default::default()
+        }
+    }
+}
+
+impl From<Circle> for RegularPolygon {
+    fn from(circle: Circle) -> Self {
+        Self {
+            radius: circle.radius,
+            sides: circle.vertices,
+        }
+    }
+}
+
+impl From<Circle> for Mesh {
+    fn from(circle: Circle) -> Self {
+        Mesh::from(RegularPolygon::from(circle))
+    }
+}

examples/2d/shapes.rs

@@ -0,0 +1,42 @@
+use bevy::{prelude::*, sprite::MaterialMesh2dBundle};
+
+fn main() {
+    App::new()
+        .add_plugins(DefaultPlugins)
+        .add_startup_system(setup)
+        .run();
+}
+
+fn setup(
+    mut commands: Commands,
+    mut meshes: ResMut<Assets<Mesh>>,
+    mut materials: ResMut<Assets<ColorMaterial>>,
+) {
+    commands.spawn_bundle(OrthographicCameraBundle::new_2d());
+
+    // Rectangle
+    commands.spawn_bundle(SpriteBundle {
+        sprite: Sprite {
+            color: Color::rgb(0.25, 0.25, 0.75),
+            custom_size: Some(Vec2::new(50.0, 100.0)),
+            ..default()
+        },
+        ..default()
+    });
+
+    // Circle
+    commands.spawn_bundle(MaterialMesh2dBundle {
+        mesh: meshes.add(shape::Circle::new(50.).into()).into(),
+        material: materials.add(ColorMaterial::from(Color::PURPLE)),
+        transform: Transform::from_translation(Vec3::new(-100., 0., 0.)),
+        ..default()
+    });
+
+    // Hexagon
+    commands.spawn_bundle(MaterialMesh2dBundle {
+        mesh: meshes.add(shape::RegularPolygon::new(50., 6).into()).into(),
+        material: materials.add(ColorMaterial::from(Color::TURQUOISE)),
+        transform: Transform::from_translation(Vec3::new(100., 0., 0.)),
+        ..default()
+    });
+}

examples/README.md

@@ -87,7 +87,7 @@ Example | File | Description
 `move_sprite` | [`2d/move_sprite.rs`](./2d/move_sprite.rs) | Changes the transform of a sprite.
 `mesh2d` | [`2d/mesh2d.rs`](./2d/mesh2d.rs) | Renders a 2d mesh
 `mesh2d_manual` | [`2d/mesh2d_manual.rs`](./2d/mesh2d_manual.rs) | Renders a custom mesh "manually" with "mid-level" renderer apis.
-`rect` | [`2d/rect.rs`](./2d/rect.rs) | Renders a rectangle
+`shapes` | [`2d/shapes.rs`](./2d/shapes.rs) | Renders a rectangle, circle, and hexagon
 `sprite` | [`2d/sprite.rs`](./2d/sprite.rs) | Renders a sprite
 `sprite_sheet` | [`2d/sprite_sheet.rs`](./2d/sprite_sheet.rs) | Renders an animated sprite
 `text2d` | [`2d/text2d.rs`](./2d/text2d.rs) | Generates text in 2d