Only generate starfield when necessary

src/main.rs

@@ -165,6 +165,8 @@ pub async fn run() -> Result<()> {
 	let mut gpu = GPUState::new(window).await?;
 	let mut game = Game::new();
 
+	gpu.on_new_system(&game);
+
 	event_loop.run(move |event, _, control_flow| {
 		match event {
 			Event::RedrawRequested(window_id) if window_id == gpu.window().id() => {

src/render/gpustate.rs

@@ -30,6 +30,7 @@ pub struct GPUState {
 
 	sprite_pipeline: wgpu::RenderPipeline,
 	starfield_pipeline: wgpu::RenderPipeline,
+	starfield_count: u32,
 
 	texture_array: TextureArray,
 	global_data: GlobalData,
@@ -179,6 +180,7 @@ impl GPUState {
 			texture_array,
 			global_data,
 			vertex_buffers,
+			starfield_count: 0,
 		});
 	}
 
@@ -252,17 +254,28 @@ impl GPUState {
 	/// Will panic if STARFIELD_INSTANCE_LIMIT is exceeded.
 	///
 	/// This is only called inside self.render()
-	fn make_starfield_instances(&self, game: &Game) -> Vec<StarfieldInstance> {
-		let instances: Vec<StarfieldInstance> = game
-			.system
-			.starfield
-			.iter()
-			.map(|s| StarfieldInstance {
-				position: s.pos.into(),
-				parallax: s.parallax,
-				height: s.height,
-			})
-			.collect();
+	fn make_starfield_instances(&mut self, game: &Game) -> Vec<StarfieldInstance> {
+		let mut instances = Vec::new();
+		let sz = STARFIELD_SIZE as f32;
+		for offset in [
+			Vector2 { x: 0.0, y: 0.0 },
+			Vector2 { x: 0.0, y: sz },
+			Vector2 { x: sz, y: sz },
+			Vector2 { x: sz, y: 0.0 },
+			Vector2 { x: sz, y: -sz },
+			Vector2 { x: 0.0, y: -sz },
+			Vector2 { x: -sz, y: -sz },
+			Vector2 { x: -sz, y: 0.0 },
+			Vector2 { x: -sz, y: sz },
+		] {
+			for s in &game.system.starfield {
+				instances.push(StarfieldInstance {
+					position: (s.pos + offset).into(),
+					parallax: s.parallax,
+					height: s.height,
+				})
+			}
+		}
 
 		// Enforce starfield limit
 		if instances.len() as u64 > Self::STARFIELD_INSTANCE_LIMIT {
@@ -270,9 +283,20 @@ impl GPUState {
 			unreachable!("Starfield limit exceeded!")
 		}
 
+		self.starfield_count = instances.len() as u32;
 		return instances;
 	}
 
+	pub fn on_new_system(&mut self, game: &Game) {
+		// Create starfield instances
+		let starfield_instances = self.make_starfield_instances(game);
+		self.queue.write_buffer(
+			&self.vertex_buffers.starfield.instances,
+			0,
+			bytemuck::cast_slice(&starfield_instances),
+		);
+	}
+
 	pub fn render(&mut self, game: &Game) -> Result<(), wgpu::SurfaceError> {
 		let output = self.surface.get_current_texture()?;
 		let view = output
@@ -328,14 +352,6 @@ impl GPUState {
 			bytemuck::cast_slice(&sprite_instances),
 		);
 
-		// Create starfield instances
-		let starfield_instances = self.make_starfield_instances(game);
-		self.queue.write_buffer(
-			&self.vertex_buffers.starfield.instances,
-			0,
-			bytemuck::cast_slice(&starfield_instances),
-		);
-
 		// These should match the indices in each shader,
 		// and should each have a corresponding bind group layout.
 		render_pass.set_bind_group(0, &self.texture_array.bind_group, &[]);
@@ -344,13 +360,7 @@ impl GPUState {
 		// Starfield pipeline
 		self.vertex_buffers.starfield.set_in_pass(&mut render_pass);
 		render_pass.set_pipeline(&self.starfield_pipeline);
-
-		render_pass.draw(0..1, 0..starfield_instances.len() as _);
-		render_pass.draw_indexed(
-			0..SPRITE_INDICES.len() as u32,
-			0,
-			0..starfield_instances.len() as _,
-		);
+		render_pass.draw_indexed(0..SPRITE_INDICES.len() as u32, 0, 0..self.starfield_count);
 
 		// Sprite pipeline
 		self.vertex_buffers.sprite.set_in_pass(&mut render_pass);