add an example for sprites with a custom shape

Cargo.toml

@@ -104,6 +104,10 @@ path = "examples/hello_world.rs"
 name = "contributors"
 path = "examples/2d/contributors.rs"
 
+[[example]]
+name = "custom_sprites"
+path = "examples/2d/custom_sprites.rs"
+
 [[example]]
 name = "mesh"
 path = "examples/2d/mesh.rs"

examples/2d/custom_sprites.rs

@@ -0,0 +1,157 @@
+use bevy::prelude::*;
+
+// This example shows how to use a custom mesh with a `SpriteBundle`. It won't go into most
+// of the details of the mesh creation, as those are covered by the example 2d/mesh.rs, which
+// use a `MeshBundle`. The `SpriteBundle` has two more components:
+// - `Handle<ColorMaterial>` used to specify either the color or the texture
+// - `Sprite` used to set the size of the image
+// These two components let us use the default pipeline instead of defining our own with
+// a custom shader as can be seen in the mesh example, but are less flexible if you need
+// to do custom things for the color
+
+fn main() {
+    App::new()
+        .add_plugins(DefaultPlugins)
+        .add_startup_system(camera)
+        // We will do two shapes: stars and discs, they are both simple meshes to generate
+        .add_startup_system(stars)
+        .add_startup_system(discs)
+        .run();
+}
+
+fn camera(mut commands: Commands) {
+    commands.spawn_bundle(OrthographicCameraBundle::new_2d());
+}
+
+// Number of points the generated polygons will have
+// For stars, the more points, the pointier the star will be. A 5 points star is a pentagram
+// For discs, the more points, the roundier the disc will be. A 3 points disc is a triangle
+const POINTS: [u32; 10] = [3, 4, 5, 6, 7, 8, 10, 15, 30, 50];
+
+fn stars(
+    mut commands: Commands,
+    mut meshes: ResMut<Assets<Mesh>>,
+    mut materials: ResMut<Assets<ColorMaterial>>,
+    asset_server: Res<AssetServer>,
+) {
+    let texture_handle = asset_server.load("branding/icon.png");
+    let material = materials.add(texture_handle.into());
+
+    // We will do two lines of stars: one with a texture, the other with a plain color
+    let with_image = SpriteBundle {
+        // Use the material for the texture
+        material: material.clone(),
+        ..Default::default()
+    };
+
+    let with_plain_color = SpriteBundle {
+        // Use the material for a plain color
+        material: materials.add(Color::rgb(0.25, 0.25, 0.75).into()),
+        ..Default::default()
+    };
+
+    for (line, basis) in [with_image, with_plain_color].iter().enumerate() {
+        for (pos, star_points) in POINTS.iter().enumerate() {
+            let mut star = Mesh::new(bevy::render::pipeline::PrimitiveTopology::TriangleList);
+
+            let mut v_pos = vec![[0.0, 0.0, 0.0]];
+            // The default pipeline needs two other mesh attributes:
+            // - Normals - it can be ignored in 2d and just use `[0.0, 0.0, 1.0]` for every point
+            // - UVs - it's the position of the 2d texture applied to the mesh. While
+            // `[0.0, 0.0, 0.0]` is the center of the mesh, `[0.0, 0.0]` is the top left corner
+            // of the texture
+            let mut v_normals = vec![[0.0, 0.0, 1.0]];
+            let mut v_uvs = vec![[0.5, 0.5]];
+
+            for i in 0..(star_points * 2) {
+                let a = std::f32::consts::FRAC_PI_2
+                    - i as f32 * std::f32::consts::TAU / (star_points * 2) as f32;
+                let r = if i % 2 == 0 { 1.0 } else { 0.4 };
+                v_pos.push([r * a.cos(), r * a.sin(), 0.0]);
+                // Just use the same normal for every point
+                v_normals.push([0.0, 0.0, 1.0]);
+                // Those UV values won't deform the original image, but will cut parts that are
+                // out of the star.
+                v_uvs.push([(r * a.cos() + 1.0) / 2.0, 1.0 - (r * a.sin() + 1.0) / 2.0]);
+            }
+            star.set_attribute(Mesh::ATTRIBUTE_POSITION, v_pos);
+            star.set_attribute(Mesh::ATTRIBUTE_NORMAL, v_normals);
+            star.set_attribute(Mesh::ATTRIBUTE_UV_0, v_uvs);
+
+            let mut indices = vec![0, 1, (star_points * 2)];
+            for i in 2..=(star_points * 2) {
+                indices.extend_from_slice(&[0, i, i - 1]);
+            }
+            star.set_indices(Some(bevy::render::mesh::Indices::U32(indices)));
+
+            commands.spawn_bundle(SpriteBundle {
+                mesh: meshes.add(star),
+                sprite: Sprite::new(Vec2::new(50., 50.)),
+                transform: Transform::from_xyz(
+                    (pos as f32 - POINTS.len() as f32 / 2.0 + 0.5) * 110.0,
+                    (line as f32 + 0.5) * 110.0,
+                    0.0,
+                ),
+                ..basis.clone()
+            });
+        }
+    }
+}
+
+fn discs(
+    mut commands: Commands,
+    mut meshes: ResMut<Assets<Mesh>>,
+    mut materials: ResMut<Assets<ColorMaterial>>,
+    asset_server: Res<AssetServer>,
+) {
+    let texture_handle = asset_server.load("branding/icon.png");
+    let material = materials.add(texture_handle.into());
+
+    let with_image = SpriteBundle {
+        material: material.clone(),
+        ..Default::default()
+    };
+
+    let with_plain_color = SpriteBundle {
+        material: materials.add(Color::rgb(0.25, 0.75, 0.25).into()),
+        ..Default::default()
+    };
+
+    for (line, basis) in [with_image, with_plain_color].iter().enumerate() {
+        for (pos, disc_points) in POINTS.iter().enumerate() {
+            let mut disc = Mesh::new(bevy::render::pipeline::PrimitiveTopology::TriangleList);
+
+            let mut v_pos = vec![[0.0, 0.0, 0.0]];
+            let mut v_normals = vec![[0.0, 0.0, 1.0]];
+            let mut v_uvs = vec![[0.5, 0.5]];
+
+            for i in 0..*disc_points {
+                let a = std::f32::consts::FRAC_PI_2
+                    - i as f32 * std::f32::consts::TAU / (*disc_points as f32);
+                v_pos.push([a.cos(), a.sin(), 0.0]);
+                v_normals.push([0.0, 0.0, 1.0]);
+                v_uvs.push([(a.cos() + 1.0) / 2.0, 1.0 - (a.sin() + 1.0) / 2.0]);
+            }
+            disc.set_attribute(Mesh::ATTRIBUTE_POSITION, v_pos);
+            disc.set_attribute(Mesh::ATTRIBUTE_NORMAL, v_normals);
+            disc.set_attribute(Mesh::ATTRIBUTE_UV_0, v_uvs);
+
+            let mut indices = vec![0, 1, *disc_points];
+            for i in 2..=*disc_points {
+                indices.extend_from_slice(&[0, i, i - 1]);
+            }
+            disc.set_indices(Some(bevy::render::mesh::Indices::U32(indices)));
+
+            commands.spawn_bundle(SpriteBundle {
+                mesh: meshes.add(disc),
+                sprite: Sprite::new(Vec2::new(50., 50.)),
+                transform: Transform::from_xyz(
+                    (pos as f32 - POINTS.len() as f32 / 2.0 + 0.5) * 110.0,
+                    (line as f32 - 1.5) * 110.0,
+                    0.0,
+                ),
+                ..basis.clone()
+            });
+        }
+    }
+}

examples/README.md

@@ -83,6 +83,7 @@ Example | File | Description
 Example | File | Description
 --- | --- | ---
 `contributors` | [`2d/contributors.rs`](./2d/contributors.rs) | Displays each contributor as a bouncy bevy-ball!
+`custom_sprites` | [`2d/custom_sprites.rs`](2d/custom_sprites.rs) | Renders sprites with a custom shape
 `many_sprites` | [`2d/many_sprites.rs`](./2d/many_sprites.rs) | Displays many sprites in a grid arragement! Used for performance testing.
 `mesh` | [`2d/mesh.rs`](./2d/mesh.rs) | Renders a custom mesh
 `sprite` | [`2d/sprite.rs`](./2d/sprite.rs) | Renders a sprite