From 7441ac1a01d1f875747765227f6d9bfc807551cf Mon Sep 17 00:00:00 2001
From: Carter Anderson <mcanders1@gmail.com>
Date: Fri, 26 Jun 2020 21:40:09 -0700
Subject: [PATCH] add breakout example game

---
 Cargo.toml                             |   4 +
 crates/bevy_sprite/src/collide_aabb.rs |  62 +++++++
 crates/bevy_sprite/src/lib.rs          |   1 +
 crates/bevy_sprite/src/sprite.rs       |   2 +-
 examples/game/breakout/main.rs         | 231 +++++++++++++++++++++++++
 5 files changed, 299 insertions(+), 1 deletion(-)
 create mode 100644 crates/bevy_sprite/src/collide_aabb.rs
 create mode 100644 examples/game/breakout/main.rs

diff --git a/Cargo.toml b/Cargo.toml
index 3479df334a..376d4cef3c 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -139,6 +139,10 @@ path = "examples/ecs/startup_system.rs"
 name = "ecs_guide"
 path = "examples/ecs/ecs_guide.rs"
 
+[[example]]
+name = "breakout"
+path = "examples/game/breakout/main.rs"
+
 [[example]]
 name = "mouse_input"
 path = "examples/input/mouse_input.rs"
diff --git a/crates/bevy_sprite/src/collide_aabb.rs b/crates/bevy_sprite/src/collide_aabb.rs
new file mode 100644
index 0000000000..021f395eca
--- /dev/null
+++ b/crates/bevy_sprite/src/collide_aabb.rs
@@ -0,0 +1,62 @@
+use glam::{Vec3, Vec2};
+
+#[derive(Debug)]
+pub enum Collision {
+    Left,
+    Right,
+    Top,
+    Bottom,
+}
+
+// TODO: ideally we can remove this once bevy gets a physics system
+/// Axis-aligned bounding box collision with "side" detection
+pub fn collide(a_pos: Vec3, a_size: Vec2, b_pos: Vec3, b_size: Vec2) -> Option<Collision> {
+    let a_min = a_pos.truncate() - a_size / 2.0;
+    let a_max = a_pos.truncate() + a_size / 2.0;
+
+    let b_min = b_pos.truncate() - b_size / 2.0;
+    let b_max = b_pos.truncate() + b_size / 2.0;
+
+    // check to see if the two rectangles are intersecting
+    if a_min.x() < b_max.x()
+        && a_max.x() > b_min.x()
+        && a_min.y() < b_max.y()
+        && a_max.y() > b_min.y()
+    {
+        // check to see if we hit on the left or right side
+        let (x_collision, x_depth) =
+            if a_min.x() < b_min.x() && a_max.x() > b_min.x() && a_max.x() < b_max.x() {
+                (Some(Collision::Left), b_min.x() - a_max.x())
+            } else if a_min.x() > b_min.x() && a_min.x() < b_max.x() && a_max.x() > b_max.x() {
+                (Some(Collision::Right), a_min.x() - b_max.x())
+            } else {
+                (None, 0.0)
+            };
+
+        // check to see if we hit on the top or bottom side
+        let (y_collision, y_depth) =
+            if a_min.y() < b_min.y() && a_max.y() > b_min.y() && a_max.y() < b_max.y() {
+                (Some(Collision::Bottom), b_min.y() - a_max.y())
+            } else if a_min.y() > b_min.y() && a_min.y() < b_max.y() && a_max.y() > b_max.y() {
+                (Some(Collision::Top), a_min.y() - b_max.y())
+            } else {
+                (None, 0.0)
+            };
+
+        // if we had an "x" and a "y" collision, pick the "primary" side using penetration depth
+        match (x_collision, y_collision) {
+            (Some(x_collision), Some(y_collision)) => {
+                if y_depth < x_depth {
+                    Some(y_collision)
+                } else {
+                    Some(x_collision)
+                }
+            }
+            (Some(x_collision), None) => Some(x_collision),
+            (None, Some(y_collision)) => Some(y_collision),
+            (None, None) => None,
+        }
+    } else {
+        None
+    }
+}
diff --git a/crates/bevy_sprite/src/lib.rs b/crates/bevy_sprite/src/lib.rs
index 5c795b4e9d..eccd4e247c 100644
--- a/crates/bevy_sprite/src/lib.rs
+++ b/crates/bevy_sprite/src/lib.rs
@@ -1,6 +1,7 @@
 mod color_material;
 mod dynamic_texture_atlas_builder;
 pub mod entity;
+pub mod collide_aabb;
 mod rect;
 mod render;
 mod sprite;
diff --git a/crates/bevy_sprite/src/sprite.rs b/crates/bevy_sprite/src/sprite.rs
index 2021244a32..4d8700ba3c 100644
--- a/crates/bevy_sprite/src/sprite.rs
+++ b/crates/bevy_sprite/src/sprite.rs
@@ -12,7 +12,7 @@ use glam::Vec2;
 #[derive(Default, RenderResources, RenderResource)]
 #[render_resources(from_self)]
 pub struct Sprite {
-    size: Vec2,
+    pub size: Vec2,
 }
 
 // SAFE: sprite is repr(C) and only consists of byteables
diff --git a/examples/game/breakout/main.rs b/examples/game/breakout/main.rs
new file mode 100644
index 0000000000..7239c4fefe
--- /dev/null
+++ b/examples/game/breakout/main.rs
@@ -0,0 +1,231 @@
+use bevy::{
+    prelude::*,
+    sprite::collide_aabb::{collide, Collision},
+};
+
+fn main() {
+    App::build()
+        .add_default_plugins()
+        .add_resource(ClearColor(Color::rgb(0.7, 0.7, 0.7)))
+        .add_startup_system(setup.system())
+        .add_system(paddle_movement_system.system())
+        .add_system(ball_collision_system.system())
+        .add_system(ball_movement_system.system())
+        .run();
+}
+
+struct Paddle {
+    speed: f32,
+}
+
+struct Ball {
+    velocity: Vec3,
+}
+
+struct Brick;
+struct Wall;
+
+fn setup(command_buffer: &mut CommandBuffer, mut materials: ResMut<Assets<ColorMaterial>>) {
+    // Add the game's entities to our world
+    let mut builder = command_buffer.build();
+    builder
+        // camera
+        .entity_with(OrthographicCameraComponents::default())
+        // paddle
+        .entity_with(SpriteComponents {
+            material: materials.add(Color::rgb(0.2, 0.2, 0.8).into()),
+            translation: Translation(Vec3::new(0.0, -250.0, 0.0)),
+            sprite: Sprite {
+                size: Vec2::new(120.0, 30.0),
+            },
+            ..Default::default()
+        })
+        .with(Paddle { speed: 500.0 })
+        // ball
+        .entity_with(SpriteComponents {
+            material: materials.add(Color::rgb(0.8, 0.2, 0.2).into()),
+            translation: Translation(Vec3::new(0.0, -100.0, 1.0)),
+            sprite: Sprite {
+                size: Vec2::new(30.0, 30.0),
+            },
+            ..Default::default()
+        })
+        .with(Ball {
+            velocity: 400.0 * Vec3::new(0.5, -0.5, 0.0).normalize(),
+        });
+
+    // Add walls
+    let wall_material = materials.add(Color::rgb(0.5, 0.5, 0.5).into());
+    let wall_thickness = 10.0;
+    let bounds = Vec2::new(900.0, 600.0);
+
+    builder
+        // left
+        .entity_with(SpriteComponents {
+            material: wall_material,
+            translation: Translation(Vec3::new(-bounds.x() / 2.0, 0.0, 0.0)),
+            sprite: Sprite {
+                size: Vec2::new(wall_thickness, bounds.y() + wall_thickness),
+            },
+            ..Default::default()
+        })
+        .with(Wall)
+        // right
+        .entity_with(SpriteComponents {
+            material: wall_material,
+            translation: Translation(Vec3::new(bounds.x() / 2.0, 0.0, 0.0)),
+            sprite: Sprite {
+                size: Vec2::new(wall_thickness, bounds.y() + wall_thickness),
+            },
+            ..Default::default()
+        })
+        .with(Wall)
+        // bottom
+        .entity_with(SpriteComponents {
+            material: wall_material,
+            translation: Translation(Vec3::new(0.0, -bounds.y() / 2.0, 0.0)),
+            sprite: Sprite {
+                size: Vec2::new(bounds.x() + wall_thickness, wall_thickness),
+            },
+            ..Default::default()
+        })
+        .with(Wall)
+        // top
+        .entity_with(SpriteComponents {
+            material: wall_material,
+            translation: Translation(Vec3::new(0.0, bounds.y() / 2.0, 0.0)),
+            sprite: Sprite {
+                size: Vec2::new(bounds.x() + wall_thickness, wall_thickness),
+            },
+            ..Default::default()
+        })
+        .with(Wall);
+
+    // Add bricks
+    let brick_rows = 4;
+    let brick_columns = 5;
+    let brick_spacing = 20.0;
+    let brick_size = Vec2::new(150.0, 30.0);
+    let bricks_width = brick_columns as f32 * (brick_size.x() + brick_spacing) - brick_spacing;
+    // center the bricks and move them up a bit
+    let bricks_offset = Vec3::new(-(bricks_width - brick_size.x()) / 2.0, 100.0, 0.0);
+
+    for row in 0..brick_rows {
+        let y_position = row as f32 * (brick_size.y() + brick_spacing);
+        for column in 0..brick_columns {
+            let brick_position = Vec3::new(
+                column as f32 * (brick_size.x() + brick_spacing),
+                y_position,
+                0.0,
+            ) + bricks_offset;
+            builder
+                // brick
+                .entity_with(SpriteComponents {
+                    material: materials.add(Color::rgb(0.2, 0.2, 0.8).into()),
+                    sprite: Sprite { size: brick_size },
+                    translation: Translation(brick_position),
+                    ..Default::default()
+                })
+                .with(Brick);
+        }
+    }
+}
+
+fn paddle_movement_system(
+    world: &mut SubWorld,
+    time: Res<Time>,
+    keyboard_input: Res<Input<KeyCode>>,
+    query: &mut Query<(Read<Paddle>, Write<Translation>)>,
+) {
+    for (paddle, mut translation) in query.iter_mut(world) {
+        let mut direction = 0.0;
+        if keyboard_input.pressed(KeyCode::Left) {
+            direction -= 1.0;
+        }
+
+        if keyboard_input.pressed(KeyCode::Right) {
+            direction += 1.0;
+        }
+
+        *translation.0.x_mut() += time.delta_seconds * direction * paddle.speed;
+    }
+}
+
+fn ball_movement_system(
+    world: &mut SubWorld,
+    time: Res<Time>,
+    ball_query: &mut Query<(Read<Ball>, Write<Translation>)>,
+) {
+    for (ball, mut translation) in ball_query.iter_mut(world) {
+        translation.0 += ball.velocity * time.delta_seconds;
+    }
+}
+
+fn ball_collision_system(
+    command_buffer: &mut CommandBuffer,
+    world: &mut SubWorld,
+    ball_query: &mut Query<(Write<Ball>, Read<Translation>, Read<Sprite>)>,
+    paddle_query: &mut Query<(Read<Paddle>, Read<Translation>, Read<Sprite>)>,
+    brick_query: &mut Query<(Read<Brick>, Read<Translation>, Read<Sprite>)>,
+    wall_query: &mut Query<(Read<Wall>, Read<Translation>, Read<Sprite>)>,
+) {
+    for (mut ball, translation, sprite) in ball_query.iter_mut(world) {
+        let ball_position = translation.0;
+        let ball_size = sprite.size;
+        let velocity = &mut ball.velocity;
+        let mut collision = None;
+
+        // check collision with walls
+        for (_wall, translation, sprite) in wall_query.iter(world) {
+            if collision.is_some() {
+                break;
+            }
+
+            collision = collide(ball_position, ball_size, translation.0, sprite.size);
+        }
+
+        // check collision with paddle(s)
+        for (_paddle, translation, sprite) in paddle_query.iter(world) {
+            if collision.is_some() {
+                break;
+            }
+
+            collision = collide(ball_position, ball_size, translation.0, sprite.size);
+        }
+
+        // check collision with bricks
+        for (brick_entity, (_brick, translation, sprite)) in brick_query.iter_entities(world) {
+            if collision.is_some() {
+                break;
+            }
+
+            collision = collide(ball_position, ball_size, translation.0, sprite.size);
+            if collision.is_some() {
+                command_buffer.delete(brick_entity);
+            }
+        }
+
+        // reflect the ball when it collides
+        let mut reflect_x = false;
+        let mut reflect_y = false;
+
+        // only reflect if the ball's velocity is going in the opposite direction of the collision
+        match collision {
+            Some(Collision::Left) => reflect_x = velocity.x() > 0.0,
+            Some(Collision::Right) => reflect_x = velocity.x() < 0.0,
+            Some(Collision::Top) => reflect_y = velocity.y() < 0.0,
+            Some(Collision::Bottom) => reflect_y = velocity.y() > 0.0,
+            None => {}
+        }
+
+        // reflect velocity on the x-axis if we hit something on the x-axis
+        if reflect_x {
+            *velocity.x_mut() = -velocity.x();
+        }
+
+        // reflect velocity on the y-axis if we hit something on the y-axis
+        if reflect_y {
+            *velocity.y_mut() = -velocity.y();
+        }
+    }
+}