Fixed parallax

src/main.rs

@@ -1,5 +1,5 @@
 use anyhow::Result;
-use cgmath::{Deg, EuclideanSpace, Point2};
+use cgmath::{Deg, Point2};
 use winit::{
 	event::{
 		ElementState, Event, KeyboardInput, MouseButton, MouseScrollDelta, TouchPhase,
@@ -65,20 +65,6 @@ struct Sprite {
 	parallax: Pfloat,
 }
 
-impl Sprite {
-	const PARALLAX_STRENGTH: Pfloat = 0.1;
-
-	pub fn post_parallax(parallax: Pfloat, pos: Point2<Pfloat>, camera: Camera) -> Point2<Pfloat> {
-		let v = camera.pos.to_vec() - pos.to_vec();
-		return pos + (v * parallax * Self::PARALLAX_STRENGTH);
-	}
-
-	/// Returns post-parallax position in game coordinates.
-	pub fn post_parallax_position(&self, camera: Camera) -> Point2<Pfloat> {
-		return Self::post_parallax(self.parallax, self.pos, camera);
-	}
-}
-
 struct Game {
 	input: InputStatus,
 	last_update: Instant,

src/render/gpustate.rs

@@ -211,7 +211,8 @@ impl GPUState {
 		let clip_sw = Point2::from((1.0, -1.0)) * game.camera.zoom;
 
 		for s in game.sprites() {
-			let pos = s.post_parallax_position(game.camera) - game.camera.pos.to_vec();
+			// Parallax is computed here, so we can check if this sprite is visible.
+			let pos = (s.pos - game.camera.pos.to_vec()) / s.parallax;
 			let texture = self.texture_array.get_texture(&s.name[..]);
 
 			// Game dimensions of this sprite post-scale.
@@ -263,17 +264,16 @@ impl GPUState {
 	///
 	/// This is only called inside self.render()
 	fn make_starfield_instances(&self, game: &Game) -> Vec<StarfieldInstance> {
-		let mut instances = Vec::new();
+		let instances: Vec<StarfieldInstance> = game
-		for s in &game.system.starfield {
+			.system
-			// TODO: minimize operations here
+			.starfield
-			//let pos = Sprite::post_parallax(s.parallax, s.pos * 500.0, game.camera)
+			.iter()
-			//	- game.camera.pos.to_vec();
+			.map(|s| StarfieldInstance {
-			instances.push(StarfieldInstance {
 				position: s.pos.into(),
 				parallax: s.parallax,
-				height: 2.0,
+				height: s.height,
-			});
+			})
-		}
+			.collect();
 
 		// Enforce starfield limit
 		if instances.len() as u64 > Self::STARFIELD_INSTANCE_LIMIT {
@@ -326,7 +326,7 @@ impl GPUState {
 				camera_zoom: game.camera.zoom,
 				window_aspect: self.window_aspect,
 				starfield_texture: 1,
-				starfield_tile_size: 1000.0,
+				starfield_tile_size: 80000.0,
 				padding: Default::default(),
 			}]),
 		);

src/render/shaders/starfield.wgsl

@@ -60,18 +60,16 @@ fn vertex_shader_main(
 	// (Note that instance position is in a different
 	// coordinate system than usual)
 	let camera_pos = (instance.position + tile_center) - global.camera_position;
-	let parallax_vector = -camera_pos * instance.parallax * 0.1;
 
 	// Translate
 	pos = pos + (
 		// Don't forget to correct distance for screen aspect ratio too!
-		// The minus in "minus parallax_vector" is important.
+		(camera_pos / (global.camera_zoom * instance.parallax))
-		((camera_pos + parallax_vector) / global.camera_zoom)
 		/ vec2<f32>(global.window_aspect, 1.0)
 	);
 
 	var out: VertexOutput;
-	out.position = vec4<f32>(pos, 0.0, 1.0);
+	out.position = vec4<f32>(pos, 0.0, 1.0) * instance.parallax;
 	out.texture_coords = vertex.texture_coords;
 	return out;
 }

src/ship.rs

@@ -41,7 +41,7 @@ impl Spriteable for Ship {
 			name: self.kind.sprite().to_owned(),
 			angle: self.body.angle,
 			scale: 1.0,
-			parallax: 0.0,
+			parallax: 1.0,
 			height: self.kind.height(),
 		};
 	}

src/system.rs

@@ -10,6 +10,7 @@ pub struct StarfieldStar {
 	// These are relative to the center of a starfield tile.
 	pub pos: Point2<Pfloat>,
 	pub parallax: Pfloat,
+	pub height: Pfloat,
 }
 
 pub struct System {
@@ -22,13 +23,14 @@ impl System {
 		let mut rng = rand::thread_rng();
 		let mut s = System {
 			bodies: Vec::new(),
-			starfield: (0..500)
+			starfield: (0..1000)
 				.map(|_| StarfieldStar {
 					pos: Point2 {
-						x: rng.gen_range(-500.0..500.0),
+						x: rng.gen_range(-40000.0..40000.0),
-						y: rng.gen_range(-500.0..500.0),
+						y: rng.gen_range(-40000.0..40000.0),
 					},
-					parallax: rng.gen_range(10.0..11.0),
+					parallax: rng.gen_range(100.0..150.0),
+					height: rng.gen_range(1.0..2.0),
 				})
 				.collect(),
 		};
@@ -36,19 +38,19 @@ impl System {
 		s.bodies.push(Doodad {
 			pos: (0.0, 0.0).into(),
 			sprite: "a0".to_owned(),
-			parallax: 3.0,
+			parallax: 4.0,
 			height: 80.0,
 		});
 
 		s.bodies.push(Doodad {
 			pos: Polar {
 				center: (0.0, 0.0).into(),
-				radius: 100.0,
+				radius: 200.0,
 				angle: Deg { 0: 31.0 },
 			}
 			.to_cartesian(),
 			sprite: "earth".to_owned(),
-			parallax: 1.0,
+			parallax: 2.0,
 			height: 120.0,
 		});
 
@@ -60,7 +62,7 @@ impl System {
 			}
 			.to_cartesian(),
 			sprite: "small".to_owned(),
-			parallax: -1.0,
+			parallax: 0.5,
 			height: 50.0,
 		});