Проектная работа - MVP

Создание нового проекта

snake-game/examples/cpu_draws.rs

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+//! Example of how to draw to a texture from the CPU.
+//!
+//! You can set the values of individual pixels to whatever you want.
+//! Bevy provides user-friendly APIs that work with [`Color`]
+//! values and automatically perform any necessary conversions and encoding
+//! into the texture's native pixel format.
+
+use bevy::asset::RenderAssetUsages;
+use bevy::color::{color_difference::EuclideanDistance, palettes::css};
+use bevy::prelude::*;
+use bevy::render::render_resource::{Extent3d, TextureDimension, TextureFormat};
+use rand::{RngExt, SeedableRng};
+use rand_chacha::ChaCha8Rng;
+
+const IMAGE_WIDTH: u32 = 256;
+const IMAGE_HEIGHT: u32 = 256;
+
+fn main() {
+    App::new()
+        .add_plugins(DefaultPlugins)
+        // In this example, we will use a fixed timestep to draw a pattern on the screen
+        // one pixel at a time, so the pattern will gradually emerge over time, and
+        // the speed at which it appears is not tied to the framerate.
+        // Let's make the fixed update very fast, so it doesn't take too long. :)
+        .insert_resource(Time::<Fixed>::from_hz(1024.0))
+        .add_systems(Startup, setup)
+        .add_systems(FixedUpdate, draw)
+        .run();
+}
+
+/// Store the image handle that we will draw to, here.
+#[derive(Resource)]
+struct MyProcGenImage(Handle<Image>);
+
+#[derive(Resource)]
+struct SeededRng(ChaCha8Rng);
+
+fn setup(mut commands: Commands, mut images: ResMut<Assets<Image>>) {
+    commands.spawn(Camera2d);
+
+    // Create an image that we are going to draw into
+    let mut image = Image::new_fill(
+        // 2D image of size 256x256
+        Extent3d {
+            width: IMAGE_WIDTH,
+            height: IMAGE_HEIGHT,
+            depth_or_array_layers: 1,
+        },
+        TextureDimension::D2,
+        // Initialize it with a beige color
+        &(css::BEIGE.to_u8_array()),
+        // Use the same encoding as the color we set
+        TextureFormat::Rgba8UnormSrgb,
+        RenderAssetUsages::MAIN_WORLD | RenderAssetUsages::RENDER_WORLD,
+    );
+
+    // To make it extra fancy, we can set the Alpha of each pixel,
+    // so that it fades out in a circular fashion.
+    for y in 0..IMAGE_HEIGHT {
+        for x in 0..IMAGE_WIDTH {
+            let center = Vec2::new(IMAGE_WIDTH as f32 / 2.0, IMAGE_HEIGHT as f32 / 2.0);
+            let max_radius = IMAGE_HEIGHT.min(IMAGE_WIDTH) as f32 / 2.0;
+            let r = Vec2::new(x as f32, y as f32).distance(center);
+            let a = 1.0 - (r / max_radius).clamp(0.0, 1.0);
+
+            // Here we will set the A value by accessing the raw data bytes.
+            // (it is the 4th byte of each pixel, as per our `TextureFormat`)
+
+            // Find our pixel by its coordinates
+            let pixel_bytes = image.pixel_bytes_mut(UVec3::new(x, y, 0)).unwrap();
+            // Convert our f32 to u8
+            pixel_bytes[3] = (a * u8::MAX as f32) as u8;
+        }
+    }
+
+    // Add it to Bevy's assets, so it can be used for rendering
+    // this will give us a handle we can use
+    // (to display it in a sprite, or as part of UI, etc.)
+    let handle = images.add(image);
+
+    // Create a sprite entity using our image
+    commands.spawn(Sprite::from_image(handle.clone()));
+    commands.insert_resource(MyProcGenImage(handle));
+
+    // We're seeding the PRNG here to make this example deterministic for testing purposes.
+    // This isn't strictly required in practical use unless you need your app to be deterministic.
+    let seeded_rng = ChaCha8Rng::seed_from_u64(19878367467712);
+    commands.insert_resource(SeededRng(seeded_rng));
+}
+
+/// Every fixed update tick, draw one more pixel to make a spiral pattern
+fn draw(
+    my_handle: Res<MyProcGenImage>,
+    mut images: ResMut<Assets<Image>>,
+    // Used to keep track of where we are
+    mut i: Local<u32>,
+    mut draw_color: Local<Color>,
+    mut seeded_rng: ResMut<SeededRng>,
+) {
+    if *i == 0 {
+        // Generate a random color on first run.
+        *draw_color = Color::linear_rgb(seeded_rng.0.random(), seeded_rng.0.random(), seeded_rng.0.random());
+    }
+
+    // Get the image from Bevy's asset storage.
+    let image = images.get_mut(&my_handle.0).expect("Image not found");
+
+    // Compute the position of the pixel to draw.
+
+    let center = Vec2::new(IMAGE_WIDTH as f32 / 2.0, IMAGE_HEIGHT as f32 / 2.0);
+    let max_radius = IMAGE_HEIGHT.min(IMAGE_WIDTH) as f32 / 2.0;
+    let rot_speed = 0.0123;
+    let period = 0.12345;
+
+    let r = ops::sin(*i as f32 * period) * max_radius;
+    let xy = Vec2::from_angle(*i as f32 * rot_speed) * r + center;
+    let (x, y) = (xy.x as u32, xy.y as u32);
+
+    // Get the old color of that pixel.
+    let old_color = image.get_color_at(x, y).unwrap();
+
+    // If the old color is our current color, change our drawing color.
+    let tolerance = 1.0 / 255.0;
+    if old_color.distance(&draw_color) <= tolerance {
+        *draw_color = Color::linear_rgb(seeded_rng.0.random(), seeded_rng.0.random(), seeded_rng.0.random());
+    }
+
+    // Set the new color, but keep old alpha value from image.
+    image.set_color_at(x, y, draw_color.with_alpha(old_color.alpha())).unwrap();
+
+    *i += 1;
+}