Renamed "parallax" into 3D coordinates,

polished starfield hiding.

content/system.toml

@@ -4,9 +4,8 @@ name = "12 Autumn above"
 
 [object.star]
 sprite = "star::star"
-position = [0.0, 0.0]
+position = [0.0, 0.0, 20.0]
 size = 1000
-parallax = 20.0
 
 
 [object.earth]
@@ -14,8 +13,8 @@ sprite = "planet::earth"
 position.center = "star"
 position.radius = 4000
 position.angle = 0
+position.z = 10.0
 size = 1000
-parallax = 10.0
 
 
 [object.luna]
@@ -23,6 +22,6 @@ sprite = "planet::luna"
 position.center = "earth"
 position.radius = 1600
 position.angle = 135
+position.z = 7.8
 size = 500
 angle = -45
-parallax = 7.8

src/consts.rs

@@ -3,19 +3,29 @@ use crate::physics::Pfloat;
 pub const ZOOM_MIN: Pfloat = 200.0;
 pub const ZOOM_MAX: Pfloat = 2000.0;
 
-// Z-axis range for starfield stars
-pub const STARFIELD_PARALLAX_MIN: f32 = 100.0;
-pub const STARFIELD_PARALLAX_MAX: f32 = 200.0;
-// Size of a square starfield tile, in game units.
-// A tile of size PARALLAX_MAX * screen-size-in-game-units
-// will completely cover a (square) screen. This depends on zoom!
-//
-// Use a value smaller than zoom_max for debug.
-pub const STARFIELD_SIZE: u64 = STARFIELD_PARALLAX_MAX as u64 * ZOOM_MAX as u64;
-// Average number of stars per game unit
+/// Z-axis range for starfield stars
+/// This does not affect scale.
+pub const STARFIELD_Z_MIN: f32 = 100.0;
+pub const STARFIELD_Z_MAX: f32 = 200.0;
+
+/// Size range for starfield stars, in game units.
+/// This is scaled for zoom, but NOT for distance.
+pub const STARFIELD_SIZE_MIN: f32 = 0.2;
+pub const STARFIELD_SIZE_MAX: f32 = 1.8;
+
+/// Size of a square starfield tile, in game units.
+/// A tile of size STARFIELD_Z_MAX * screen-size-in-game-units
+/// will completely cover a (square) screen. This depends on zoom!
+///
+/// Use a value smaller than zoom_max for debug.
+pub const STARFIELD_SIZE: u64 = STARFIELD_Z_MAX as u64 * ZOOM_MAX as u64;
+
+/// Average number of stars per game unit
 pub const STARFIELD_DENSITY: f64 = 0.01;
-// Number of stars in one starfield tile
-// Must fit inside an i32
+
+/// Number of stars in one starfield tile
+/// Must fit inside an i32
 pub const STARFIELD_COUNT: u64 = (STARFIELD_SIZE as f64 * STARFIELD_DENSITY) as u64;
 
+/// Root directory of game content
 pub const CONTENT_ROOT: &'static str = "./content";

src/content/syntax/system.rs

@@ -1,5 +1,5 @@
 use anyhow::{bail, Context, Result};
-use cgmath::{Deg, Point2};
+use cgmath::{Deg, Point3};
 use std::collections::{HashMap, HashSet};
 
 use crate::physics::{Pfloat, Polar};
@@ -27,7 +27,6 @@ pub(in crate::content) mod toml {
 		pub position: Position,
 
 		pub size: Pfloat,
-		pub parallax: Pfloat,
 
 		pub radius: Option<Pfloat>,
 		pub angle: Option<Pfloat>,
@@ -37,24 +36,25 @@ pub(in crate::content) mod toml {
 	#[serde(untagged)]
 	pub enum Position {
 		Polar(PolarCoords),
-		Cartesian(Coordinates),
+		Cartesian(CoordinatesThree),
 	}
 
 	#[derive(Debug, Deserialize)]
 	pub struct PolarCoords {
-		pub center: Coordinates,
+		pub center: CoordinatesTwo,
 		pub radius: Pfloat,
 		pub angle: Pfloat,
+		pub z: Pfloat,
 	}
 
 	#[derive(Debug, Deserialize)]
 	#[serde(untagged)]
-	pub enum Coordinates {
+	pub enum CoordinatesTwo {
 		Label(String),
 		Coords([Pfloat; 2]),
 	}
 
-	impl ToString for Coordinates {
+	impl ToString for CoordinatesTwo {
 		fn to_string(&self) -> String {
 			match self {
 				Self::Label(s) => s.to_owned(),
@@ -62,6 +62,44 @@ pub(in crate::content) mod toml {
 			}
 		}
 	}
+
+	impl CoordinatesTwo {
+		/// Transform a CoordinatesThree into a CoordinatesTwo by adding a NaN z component.
+		/// Labels are not changed.
+		pub fn to_three(&self) -> CoordinatesThree {
+			match self {
+				Self::Label(s) => CoordinatesThree::Label(s.clone()),
+				Self::Coords(v) => CoordinatesThree::Coords([v[0], v[1], f32::NAN]),
+			}
+		}
+	}
+
+	#[derive(Debug, Deserialize)]
+	#[serde(untagged)]
+	pub enum CoordinatesThree {
+		Label(String),
+		Coords([Pfloat; 3]),
+	}
+
+	impl ToString for CoordinatesThree {
+		fn to_string(&self) -> String {
+			match self {
+				Self::Label(s) => s.to_owned(),
+				Self::Coords(v) => format!("{:?}", v),
+			}
+		}
+	}
+
+	impl CoordinatesThree {
+		/// Transform a CoordinatesThree into a CoordinatesTwo by deleting z component.
+		/// Labels are not changed.
+		pub fn to_two(&self) -> CoordinatesTwo {
+			match self {
+				Self::Label(s) => CoordinatesTwo::Label(s.clone()),
+				Self::Coords(v) => CoordinatesTwo::Coords([v[0], v[1]]),
+			}
+		}
+	}
 }
 
 #[derive(Debug)]
@@ -73,20 +111,20 @@ pub struct System {
 #[derive(Debug)]
 pub struct Object {
 	pub sprite: String,
-	pub position: Point2<f32>,
+	pub position: Point3<f32>,
 	pub size: Pfloat,
-	pub parallax: Pfloat,
 	pub angle: Deg<Pfloat>,
 }
 
+// Helper function for resolve_position, never called on its own.
 fn resolve_coordinates(
 	objects: &HashMap<String, toml::Object>,
-	cor: &toml::Coordinates,
+	cor: &toml::CoordinatesThree,
 	mut cycle_detector: HashSet<String>,
-) -> Result<Point2<f32>> {
+) -> Result<Point3<f32>> {
 	match cor {
-		toml::Coordinates::Coords(c) => Ok((*c).into()),
-		toml::Coordinates::Label(l) => {
+		toml::CoordinatesThree::Coords(c) => Ok((*c).into()),
+		toml::CoordinatesThree::Label(l) => {
 			if cycle_detector.contains(l) {
 				bail!(
 					"Found coordinate cycle: `{}`",
@@ -111,19 +149,28 @@ fn resolve_coordinates(
 	}
 }
 
+/// Given an object, resolve it's position as a Point3.
 fn resolve_position(
 	objects: &HashMap<String, toml::Object>,
 	obj: &toml::Object,
 	cycle_detector: HashSet<String>,
-) -> Result<Point2<f32>> {
+) -> Result<Point3<f32>> {
 	match &obj.position {
-		toml::Position::Cartesian(c) => Ok(resolve_coordinates(objects, c, cycle_detector)?),
-		toml::Position::Polar(p) => Ok(Polar {
-			center: resolve_coordinates(&objects, &p.center, cycle_detector)?,
+		toml::Position::Cartesian(c) => Ok(resolve_coordinates(objects, &c, cycle_detector)?),
+		toml::Position::Polar(p) => {
+			let r = resolve_coordinates(&objects, &p.center.to_three(), cycle_detector)?;
+			let plane = Polar {
+				center: (r.x, r.y).into(),
 				radius: p.radius,
 				angle: Deg(p.angle),
 			}
-		.to_cartesian()),
+			.to_cartesian();
+			Ok(Point3 {
+				x: plane.x,
+				y: plane.y,
+				z: p.z,
+			})
+		}
 	}
 }
 
@@ -140,7 +187,6 @@ impl System {
 				position: resolve_position(&value.object, &obj, cycle_detector)
 					.with_context(|| format!("In object {:#?}", label))?,
 				size: obj.size,
-				parallax: obj.parallax,
 				angle: Deg(obj.angle.unwrap_or(0.0)),
 			});
 		}

src/game/doodad.rs

@@ -1,11 +1,10 @@
-use cgmath::{Deg, Point2};
+use cgmath::{Deg, Point3};
 
 use crate::{physics::Pfloat, render::Sprite, render::SpriteTexture, render::Spriteable};
 
 pub struct Doodad {
 	pub sprite: SpriteTexture,
-	pub pos: Point2<Pfloat>,
-	pub parallax: Pfloat,
+	pub pos: Point3<Pfloat>,
 	pub size: Pfloat,
 	pub angle: Deg<Pfloat>,
 }
@@ -18,7 +17,6 @@ impl Spriteable for Doodad {
 			pos: self.pos,
 			angle: self.angle,
 			size: self.size,
-			parallax: self.parallax,
 		};
 	}
 }

src/game/game.rs

@@ -75,9 +75,8 @@ impl Game {
 		// Make sure sprites are drawn in the correct order
 		// (note the reversed a, b in the comparator)
 		//
-		// TODO: use a gpu depth buffer with parallax as z-coordinate?
-		// Might be overkill.
-		sprites.sort_by(|a, b| b.parallax.total_cmp(&a.parallax));
+		// TODO: use a gpu depth buffer instead.
+		sprites.sort_by(|a, b| b.pos.z.total_cmp(&a.pos.z));
 
 		return sprites;
 	}

src/game/ship.rs

@@ -41,11 +41,10 @@ impl Ship {
 impl Spriteable for Ship {
 	fn get_sprite(&self) -> Sprite {
 		return Sprite {
-			pos: self.body.pos,
+			pos: (self.body.pos.x, self.body.pos.y, 1.0).into(),
 			texture: self.kind.sprite(),
 			angle: self.body.angle,
 			scale: 1.0,
-			parallax: 1.0,
 			size: self.kind.size(),
 		};
 	}

src/game/system.rs

@@ -1,4 +1,4 @@
-use cgmath::{Point2, Vector2};
+use cgmath::{Point3, Vector2};
 use rand::{self, Rng};
 
 use super::Doodad;
@@ -9,14 +9,14 @@ use crate::{
 pub struct StarfieldStar {
 	/// Star coordinates, in world space.
 	/// These are relative to the center of a starfield tile.
-	pub pos: Point2<Pfloat>,
+	pub pos: Point3<Pfloat>,
 
-	// TODO: z-coordinate?
-	pub parallax: Pfloat,
+	/// Height in game units.
+	/// Will be scaled for zoom, but not for distance.
 	pub size: Pfloat,
 
-	/// Color/brightness variation.
-	/// See shader.
+	/// Color/brightness variation. Random between 0 and 1.
+	/// Used in starfield shader.
 	pub tint: Vector2<Pfloat>,
 }
 
@@ -35,13 +35,12 @@ impl System {
 			bodies: Vec::new(),
 			starfield: (0..consts::STARFIELD_COUNT)
 				.map(|_| StarfieldStar {
-					pos: Point2 {
+					pos: Point3 {
 						x: rng.gen_range(-sz..=sz),
 						y: rng.gen_range(-sz..=sz),
+						z: rng.gen_range(consts::STARFIELD_Z_MIN..consts::STARFIELD_Z_MAX),
 					},
-					parallax: rng
-						.gen_range(consts::STARFIELD_PARALLAX_MIN..consts::STARFIELD_PARALLAX_MAX),
-					size: rng.gen_range(0.2..0.8), // TODO: configurable
+					size: rng.gen_range(consts::STARFIELD_SIZE_MIN..consts::STARFIELD_SIZE_MAX),
 					tint: Vector2 {
 						x: rng.gen_range(0.0..=1.0),
 						y: rng.gen_range(0.0..=1.0),
@@ -55,7 +54,6 @@ impl System {
 				pos: o.position,
 				sprite: SpriteTexture(o.sprite.to_owned()),
 				size: o.size,
-				parallax: o.parallax,
 				angle: o.angle,
 			});
 		}

src/render/globaldata.rs

@@ -21,23 +21,29 @@ pub struct GlobalDataContent {
 	pub camera_position: [f32; 2],
 
 	/// Camera zoom value, in game units.
-	/// Only first component has meaning.
+	/// Second component is ignored.
 	pub camera_zoom: [f32; 2],
 
+	/// Camera zoom min and max.
+	pub camera_zoom_limits: [f32; 2],
+
 	/// Size ratio of window, in physical pixels
 	pub window_size: [f32; 2],
 
 	// Aspect ration of window
-	/// Only first component has meaning.
+	/// Second component is ignored.
 	pub window_aspect: [f32; 2],
 
 	/// Texture index of starfield sprites
-	/// Only first component has meaning.
+	/// Second component is ignored.
 	pub starfield_texture: [u32; 2],
 
 	// Size of (square) starfield tiles, in game units
-	/// Only first component has meaning.
+	/// Second component is ignored.
 	pub starfield_tile_size: [f32; 2],
+
+	// Min and max starfield star size, in game units
+	pub starfield_size_limits: [f32; 2],
 }
 
 impl GlobalDataContent {

src/render/gpustate.rs

@@ -1,6 +1,6 @@
 use anyhow::Result;
 use bytemuck;
-use cgmath::{EuclideanSpace, Matrix2, Point2, Vector2};
+use cgmath::{EuclideanSpace, Matrix2, Point2, Vector2, Vector3};
 use std::{iter, rc::Rc};
 use wgpu;
 use winit::{self, dpi::PhysicalSize, window::Window};
@@ -16,7 +16,7 @@ use super::{
 		VertexBuffer,
 	},
 };
-use crate::{consts, game::Game};
+use crate::{consts, game::Game, physics::Pfloat};
 
 pub struct GPUState {
 	device: wgpu::Device,
@@ -209,14 +209,20 @@ impl GPUState {
 		let clip_sw = Point2::from((self.window_aspect, -1.0)) * game.camera.zoom;
 
 		for s in game.get_sprites() {
-			// Parallax is computed here, so we can check if this sprite is visible.
-			let pos = (s.pos - game.camera.pos.to_vec())
-				/ (s.parallax + game.camera.zoom / consts::ZOOM_MIN);
+			// Compute post-parallax position and distance-adjusted scale.
+			// We do this here so we can check if a sprite is on the screen.
+			let pos: Point2<Pfloat> = {
+				(Point2 {
+					x: s.pos.x,
+					y: s.pos.y,
+				} - game.camera.pos.to_vec())
+					/ (s.pos.z + game.camera.zoom / consts::ZOOM_MIN)
+			};
 			let texture = self.texture_array.get_sprite_texture(s.texture);
 
 			// Game dimensions of this sprite post-scale.
 			// Don't divide by 2, we use this later.
-			let height = s.size * s.scale / s.parallax;
+			let height = s.size * s.scale / s.pos.z;
 			let width = height * texture.aspect;
 
 			// Don't draw (or compute matrices for)
@@ -233,7 +239,7 @@ impl GPUState {
 				position: pos.into(),
 				aspect: texture.aspect,
 				rotation: Matrix2::from_angle(s.angle).into(),
-				height,
+				size: height,
 				texture_index: texture.index,
 			})
 		}
@@ -262,7 +268,7 @@ impl GPUState {
 			// Parallax correction.
 			// Also, adjust v for mod to work properly
 			// (v is centered at 0)
-			let v: Point2<f32> = clip_nw * consts::STARFIELD_PARALLAX_MIN;
+			let v: Point2<f32> = clip_nw * consts::STARFIELD_Z_MIN;
 			let v_adj: Point2<f32> = (v.x + (sz / 2.0), v.y + (sz / 2.0)).into();
 
 			#[rustfmt::skip]
@@ -296,14 +302,14 @@ impl GPUState {
 		let mut instances = Vec::new();
 		for x in (-nw_tile.x)..=nw_tile.x {
 			for y in (-nw_tile.y)..=nw_tile.y {
-				let offset = Vector2 {
+				let offset = Vector3 {
 					x: sz * x as f32,
 					y: sz * y as f32,
+					z: 0.0,
 				};
 				for s in &game.system.starfield {
 					instances.push(StarfieldInstance {
 						position: (s.pos + offset).into(),
-						parallax: s.parallax,
 						size: s.size,
 						tint: s.tint.into(),
 					})
@@ -364,6 +370,7 @@ impl GPUState {
 			bytemuck::cast_slice(&[GlobalDataContent {
 				camera_position: game.camera.pos.into(),
 				camera_zoom: [game.camera.zoom, 0.0],
+				camera_zoom_limits: [consts::ZOOM_MIN, consts::ZOOM_MAX],
 				window_size: [
 					self.window_size.width as f32,
 					self.window_size.height as f32,
@@ -371,6 +378,7 @@ impl GPUState {
 				window_aspect: [self.window_aspect, 0.0],
 				starfield_texture: [self.texture_array.get_starfield_texture().index, 0],
 				starfield_tile_size: [consts::STARFIELD_SIZE as f32, 0.0],
+				starfield_size_limits: [consts::STARFIELD_SIZE_MIN, consts::STARFIELD_SIZE_MAX],
 			}]),
 		);
 

src/render/shaders/sprite.wgsl

@@ -2,7 +2,7 @@ struct InstanceInput {
 	@location(2) rotation_matrix_0: vec2<f32>,
 	@location(3) rotation_matrix_1: vec2<f32>,
 	@location(4) position: vec2<f32>,
-	@location(5) height: f32,
+	@location(5) size: f32,
 	@location(6) aspect: f32,
 	@location(7) texture_idx: u32,
 };
@@ -24,10 +24,12 @@ var<uniform> global: GlobalUniform;
 struct GlobalUniform {
 	camera_position: vec2<f32>,
 	camera_zoom: vec2<f32>,
+	camera_zoom_limits: vec2<f32>,
 	window_size: vec2<f32>,
 	window_aspect: vec2<f32>,
 	starfield_texture: vec2<u32>,
 	starfield_tile_size: vec2<f32>,
+	starfield_size_limits: vec2<f32>,
 };
 
 
@@ -47,7 +49,7 @@ fn vertex_main(
 
 	// Apply sprite aspect ratio & scale factor
 	// This must be done *before* rotation.
-	let scale = instance.height / global.camera_zoom.x;
+	let scale = instance.size / global.camera_zoom.x;
 	var pos: vec2<f32> = vec2<f32>(
 		vertex.position.x * instance.aspect * scale,
 		vertex.position.y * scale

src/render/shaders/starfield.wgsl

@@ -1,8 +1,7 @@
 struct InstanceInput {
-	@location(2) position: vec2<f32>,
-	@location(3) parallax: f32,
-	@location(4) size: f32,
-	@location(5) tint: vec2<f32>,
+	@location(2) position: vec3<f32>,
+	@location(3) size: f32,
+	@location(4) tint: vec2<f32>,
 };
 
 struct VertexInput {
@@ -21,10 +20,12 @@ var<uniform> global: GlobalUniform;
 struct GlobalUniform {
 	camera_position: vec2<f32>,
 	camera_zoom: vec2<f32>,
+	camera_zoom_limits: vec2<f32>,
 	window_size: vec2<f32>,
 	window_aspect: vec2<f32>,
 	starfield_texture: vec2<u32>,
 	starfield_tile_size: vec2<f32>,
+	starfield_size_limits: vec2<f32>,
 };
 
 
@@ -62,19 +63,37 @@ fn vertex_main(
 		)
 	);
 
+
+	let zoom_min_times = (
+		global.camera_zoom.x / global.camera_zoom_limits.x
+	);
+
+	// Hide n% of the smallest stars
+	// If we wanted a constant number of stars on the screen, we would do
+	// `let hide_fraction = 1.0 - 1.0 / (zoom_min_times * zoom_min_times);`
+	// We, however, don't want this: a bigger screen should have more stars,
+	// but not *too* many. We thus scale linearly.
+	let hide_fraction = 1.0 - 1.0 / (zoom_min_times * 0.8);
+
+	// Hide some stars at large zoom levels.
+	if (
+		instance.size < (
+			hide_fraction * (global.starfield_size_limits.y - global.starfield_size_limits.x)
+			+ (global.starfield_size_limits.x)
+		)
+	) {
+		out.position = vec4<f32>(2.0, 2.0, 0.0, 1.0);
+		return out;
+	}
+
+
 	// Apply sprite aspect ratio & scale factor
 	// also applies screen aspect ratio
+	// Note that we do NOT scale for distance here---this is intentional.
 	var scale: f32 = instance.size / global.camera_zoom.x;
 
 	// Minimum scale to prevent flicker at large zoom levels
 	var real_size = scale * global.window_size.xy;
-	// TODO: configurable.
-	// Uniform distribution!
-	if (real_size.x < 0.5 || real_size.y < 0.5) {
-		// If this star is too small, don't even show it
-		out.position = vec4<f32>(2.0, 2.0, 0.0, 1.0);
-		return out;
-	}
 	if (real_size.x < 2.0 || real_size.y < 2.0) {
 		// Otherwise, clamp to a minimum scale
 		scale = 2.0 / max(global.window_size.x, global.window_size.y);
@@ -89,16 +108,16 @@ fn vertex_main(
 	// World position relative to camera
 	// (Note that instance position is in a different
 	// coordinate system than usual)
-	let camera_pos = (instance.position + tile_center) - global.camera_position.xy;
+	let camera_pos = (instance.position.xy + tile_center) - global.camera_position.xy;
 
 	// Translate
 	pos = pos + (
 		// Don't forget to correct distance for screen aspect ratio too!
-		(camera_pos / (global.camera_zoom.x * (instance.parallax)))
+		(camera_pos / (global.camera_zoom.x * (instance.position.z)))
 		/ vec2<f32>(global.window_aspect.x, 1.0)
 	);
 
-	out.position = vec4<f32>(pos, 0.0, 1.0) * instance.parallax;
+	out.position = vec4<f32>(pos, 0.0, 1.0) * instance.position.z;
 	return out;
 }
 

src/render/sprite.rs

@@ -1,4 +1,4 @@
-use cgmath::{Deg, Point2};
+use cgmath::{Deg, Point3};
 
 use super::SpriteTexture;
 use crate::physics::Pfloat;
@@ -8,7 +8,7 @@ pub struct Sprite {
 	pub texture: SpriteTexture,
 
 	/// This object's position, in world coordinates.
-	pub pos: Point2<Pfloat>,
+	pub pos: Point3<Pfloat>,
 
 	/// The size of this sprite,
 	/// given as height in world units.
@@ -21,11 +21,6 @@ pub struct Sprite {
 	/// This sprite's rotation
 	/// (relative to north, measured ccw)
 	pub angle: Deg<Pfloat>,
-
-	/// Parallax factor.
-	/// Corresponds to z-distance, and affects
-	/// position and scale.
-	pub parallax: Pfloat,
 }
 
 pub trait Spriteable {

src/render/vertexbuffer/types.rs

@@ -36,15 +36,20 @@ impl BufferObject for TexturedVertex {
 #[repr(C)]
 #[derive(Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
 pub struct StarfieldInstance {
-	/// Position in origin field tile.
-	/// note that this is DIFFERENT from
-	/// the way we provide sprite positions!
-	pub position: [f32; 2],
-
-	/// Parallax factor (same unit as usual)
-	pub parallax: f32,
+	/// Position in the starfield.
+	///
+	/// This is NOT world position, i.e, different from sprite positioning!
+	/// The x and y coordinates here represent position relative to the center
+	/// of a starfield tile in world units, which is converted to world position
+	/// by the starfield vertex shader.
+	pub position: [f32; 3],
 
+	/// Star size, in world units. This does NOT scale with distance,
+	/// unlike sprite size.
 	pub size: f32,
+
+	/// Parameters for this star's color variation,
+	/// see the starfield fragment shader.
 	pub tint: [f32; 2],
 }
 
@@ -58,24 +63,18 @@ impl BufferObject for StarfieldInstance {
 				wgpu::VertexAttribute {
 					offset: 0,
 					shader_location: 2,
-					format: wgpu::VertexFormat::Float32x2,
-				},
-				// Parallax
-				wgpu::VertexAttribute {
-					offset: mem::size_of::<[f32; 2]>() as wgpu::BufferAddress,
-					shader_location: 3,
-					format: wgpu::VertexFormat::Float32,
+					format: wgpu::VertexFormat::Float32x3,
 				},
 				// Size
 				wgpu::VertexAttribute {
 					offset: mem::size_of::<[f32; 3]>() as wgpu::BufferAddress,
-					shader_location: 4,
+					shader_location: 3,
 					format: wgpu::VertexFormat::Float32,
 				},
 				// Tint
 				wgpu::VertexAttribute {
 					offset: mem::size_of::<[f32; 4]>() as wgpu::BufferAddress,
-					shader_location: 5,
+					shader_location: 4,
 					format: wgpu::VertexFormat::Float32x2,
 				},
 			],
@@ -91,10 +90,13 @@ pub struct SpriteInstance {
 	pub rotation: [[f32; 2]; 2],
 
 	/// World position, relative to camera
+	/// Note that this does NOT contain z-distance,
+	/// since sprite parallax and distance scaling
+	/// is applied beforehand.
 	pub position: [f32; 2],
 
 	/// Height of (unrotated) sprite in world units
-	pub height: f32,
+	pub size: f32,
 
 	// Sprite aspect ratio (width / height)
 	pub aspect: f32,
@@ -129,7 +131,7 @@ impl BufferObject for SpriteInstance {
 					shader_location: 4,
 					format: wgpu::VertexFormat::Float32x2,
 				},
-				// Height
+				// Size
 				wgpu::VertexAttribute {
 					offset: mem::size_of::<[f32; 6]>() as wgpu::BufferAddress,
 					shader_location: 5,