Improved sprite routines

src/render/globaldata.rs

@@ -0,0 +1,76 @@
+use bytemuck;
+use std::mem;
+use wgpu;
+
+pub struct GlobalData {
+	pub buffer: wgpu::Buffer,
+	pub bind_group: wgpu::BindGroup,
+	pub bind_group_layout: wgpu::BindGroupLayout,
+	pub content: GlobalDataContent,
+}
+
+#[repr(C)]
+#[derive(Debug, Copy, Clone, Default, bytemuck::Pod, bytemuck::Zeroable)]
+pub struct GlobalDataContent {
+	/// Camera position, in game units
+	pub camera_position: [f32; 2],
+
+	/// Camera zoom value, in game units
+	pub camera_zoom: f32,
+
+	/// Aspect ratio of window (width / height)
+	pub window_aspect: f32,
+
+	/// Texture index of starfield sprites
+	pub starfield_texture: u32,
+
+	// Size of (square) starfield tile, in game units
+	pub starfield_tile_size: f32,
+
+	pub padding: [f32; 3],
+}
+
+impl GlobalDataContent {
+	const SIZE: u64 = mem::size_of::<Self>() as wgpu::BufferAddress;
+}
+
+impl GlobalData {
+	pub fn new(device: &wgpu::Device) -> Self {
+		let buffer = device.create_buffer(&wgpu::BufferDescriptor {
+			label: None,
+			size: GlobalDataContent::SIZE,
+			usage: wgpu::BufferUsages::UNIFORM | wgpu::BufferUsages::COPY_DST,
+			mapped_at_creation: false,
+		});
+
+		let bind_group_layout = device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
+			entries: &[wgpu::BindGroupLayoutEntry {
+				binding: 0,
+				visibility: wgpu::ShaderStages::VERTEX_FRAGMENT,
+				ty: wgpu::BindingType::Buffer {
+					ty: wgpu::BufferBindingType::Uniform,
+					has_dynamic_offset: false,
+					min_binding_size: None,
+				},
+				count: None,
+			}],
+			label: Some("camera_bind_group_layout"),
+		});
+
+		let bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
+			layout: &bind_group_layout,
+			entries: &[wgpu::BindGroupEntry {
+				binding: 0,
+				resource: buffer.as_entire_binding(),
+			}],
+			label: Some("camera_bind_group"),
+		});
+
+		return Self {
+			buffer,
+			bind_group,
+			bind_group_layout,
+			content: GlobalDataContent::default(),
+		};
+	}
+}

src/render/gpustate.rs

@@ -1,6 +1,6 @@
 use anyhow::Result;
 use bytemuck;
-use cgmath::{EuclideanSpace, Point2, Vector2};
+use cgmath::{EuclideanSpace, Matrix2, Point2};
 use std::{iter, rc::Rc};
 use wgpu;
 use winit::{self, dpi::PhysicalSize, window::Window};
@@ -8,12 +8,12 @@ use winit::{self, dpi::PhysicalSize, window::Window};
 use crate::Game;
 
 use super::{
+	globaldata::{GlobalData, GlobalDataContent},
 	pipeline::PipelineBuilder,
 	texturearray::TextureArray,
-	util::Transform,
 	vertexbuffer::{
 		data::{SPRITE_INDICES, SPRITE_VERTICES},
-		types::{PlainVertex, SpriteInstance, StarfieldInstance, TexturedVertex},
+		types::{SpriteInstance, StarfieldInstance, TexturedVertex},
 		VertexBuffer,
 	},
 };
@@ -32,6 +32,7 @@ pub struct GPUState {
 	starfield_pipeline: wgpu::RenderPipeline,
 
 	texture_array: TextureArray,
+	global_data: GlobalData,
 	vertex_buffers: VertexBuffers,
 }
 
@@ -44,7 +45,7 @@ impl GPUState {
 	// We can draw at most this many sprites on the screen.
 	// TODO: compile-time option
 	pub const SPRITE_INSTANCE_LIMIT: u64 = 100;
-	pub const STARFIELD_INSTANCE_LIMIT: u64 = 100;
+	pub const STARFIELD_INSTANCE_LIMIT: u64 = 501 * 9;
 
 	pub async fn new(window: Window) -> Result<Self> {
 		let window_size = window.inner_size();
@@ -118,18 +119,25 @@ impl GPUState {
 				Self::SPRITE_INSTANCE_LIMIT,
 			)),
 
-			starfield: Rc::new(VertexBuffer::new::<PlainVertex, StarfieldInstance>(
+			starfield: Rc::new(VertexBuffer::new::<TexturedVertex, StarfieldInstance>(
 				"starfield",
 				&device,
-				None,
-				None,
+				Some(SPRITE_VERTICES),
+				Some(SPRITE_INDICES),
 				Self::STARFIELD_INSTANCE_LIMIT,
 			)),
 		};
 
-		// Load textures
+		// Load uniforms
+		let global_data = GlobalData::new(&device);
 		let texture_array = TextureArray::new(&device, &queue)?;
 
+		// Make sure these match the indices in each shader
+		let bind_group_layouts = &[
+			&texture_array.bind_group_layout,
+			&global_data.bind_group_layout,
+		];
+
 		// Create render pipelines
 		let sprite_pipeline = PipelineBuilder::new("sprite", &device)
 			.set_shader(include_str!(concat!(
@@ -140,7 +148,7 @@ impl GPUState {
 			.set_format(config.format)
 			.set_triangle(true)
 			.set_vertex_buffer(&vertex_buffers.sprite)
-			.set_bind_group_layouts(&[&texture_array.bind_group_layout])
+			.set_bind_group_layouts(bind_group_layouts)
 			.build();
 
 		let starfield_pipeline = PipelineBuilder::new("starfield", &device)
@@ -150,8 +158,9 @@ impl GPUState {
 				"starfield.wgsl"
 			)))
 			.set_format(config.format)
-			.set_triangle(false)
+			.set_triangle(true)
 			.set_vertex_buffer(&vertex_buffers.starfield)
+			.set_bind_group_layouts(bind_group_layouts)
 			.build();
 
 		return Ok(Self {
@@ -168,6 +177,7 @@ impl GPUState {
 			starfield_pipeline,
 
 			texture_array,
+			global_data,
 			vertex_buffers,
 		});
 	}
@@ -229,19 +239,12 @@ impl GPUState {
 			//
 			// We can't use screen_pos to exclude off-screen sprites because
 			// it can't account for height and width.
-			let scale = height / game.camera.zoom;
-			let screen_pos: Point2<f32> = pos / game.camera.zoom;
 
 			instances.push(SpriteInstance {
-				transform: Transform {
-					pos: screen_pos,
-					sprite_aspect: texture.aspect,
-					window_aspect: self.window_aspect,
-					rotate: s.angle,
-					scale,
-				}
-				.to_matrix()
-				.into(),
+				position: pos.into(),
+				aspect: texture.aspect,
+				rotation: Matrix2::from_angle(s.angle).into(),
+				height,
 				texture_index: texture.index,
 			})
 		}
@@ -259,22 +262,25 @@ 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> = (-10..10)
-			.map(|x| StarfieldInstance {
-				position: Vector2 {
-					x: x as f32 / 10.0,
-					y: 0.0,
-				}
-				.into(),
-			})
-			.collect();
+	fn make_starfield_instances(&self, game: &Game) -> Vec<StarfieldInstance> {
+		let mut instances = Vec::new();
+		for s in &game.system.starfield {
+			// TODO: minimize operations here
+			//let pos = Sprite::post_parallax(s.parallax, s.pos * 500.0, game.camera)
+			//	- game.camera.pos.to_vec();
+			instances.push(StarfieldInstance {
+				position: s.pos.into(),
+				parallax: s.parallax,
+				height: 2.0,
+			});
+		}
 
 		// Enforce starfield limit
 		if instances.len() as u64 > Self::STARFIELD_INSTANCE_LIMIT {
 			// TODO: no panic, handle this better.
 			unreachable!("Starfield limit exceeded!")
 		}
+
 		return instances;
 	}
 
@@ -311,6 +317,20 @@ impl GPUState {
 			timestamp_writes: None,
 		});
 
+		// Update global values
+		self.queue.write_buffer(
+			&self.global_data.buffer,
+			0,
+			bytemuck::cast_slice(&[GlobalDataContent {
+				camera_position: game.camera.pos.into(),
+				camera_zoom: game.camera.zoom,
+				window_aspect: self.window_aspect,
+				starfield_texture: 1,
+				starfield_tile_size: 1000.0,
+				padding: Default::default(),
+			}]),
+		);
+
 		// Create sprite instances
 		let sprite_instances = self.make_sprite_instances(game);
 		self.queue.write_buffer(
@@ -327,12 +347,21 @@ impl GPUState {
 			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, &[]);
+		render_pass.set_bind_group(1, &self.global_data.bind_group, &[]);
 
 		// 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 _,
+		);
 
 		// Sprite pipeline
 		self.vertex_buffers.sprite.set_in_pass(&mut render_pass);

src/render/mod.rs

@@ -1,18 +1,17 @@
+mod globaldata;
 mod gpustate;
 mod pipeline;
 mod rawtexture;
 mod texturearray;
-mod util;
 mod vertexbuffer;
 
 pub use gpustate::GPUState;
 pub use texturearray::Texture;
 
-use cgmath::Matrix4;
-
-/// API correction matrix.
-/// cgmath uses OpenGL's matrix format, which
-/// needs to be converted to wgpu's matrix format.
+// API correction matrix.
+// cgmath uses OpenGL's matrix format, which
+// needs to be converted to wgpu's matrix format.
+/*
 #[rustfmt::skip]
 const OPENGL_TO_WGPU_MATRIX: Matrix4<f32> = Matrix4::new(
 	1.0, 0.0, 0.0, 0.0,
@@ -20,3 +19,4 @@ const OPENGL_TO_WGPU_MATRIX: Matrix4<f32> = Matrix4::new(
 	0.0, 0.0, 0.5, 0.5,
 	0.0, 0.0, 0.0, 1.0,
 );
+*/

src/render/shaders/sprite.wgsl

@@ -1,10 +1,11 @@
 // Vertex shader
 struct InstanceInput {
-	@location(2) transform_matrix_0: vec4<f32>,
-	@location(3) transform_matrix_1: vec4<f32>,
-	@location(4) transform_matrix_2: vec4<f32>,
-	@location(5) transform_matrix_3: vec4<f32>,
-	@location(6) texture_idx: u32,
+	@location(2) rotation_matrix_0: vec2<f32>,
+	@location(3) rotation_matrix_1: vec2<f32>,
+	@location(4) position: vec2<f32>,
+	@location(5) height: f32,
+	@location(6) aspect: f32,
+	@location(7) texture_idx: u32,
 };
 
 struct VertexInput {
@@ -13,26 +14,57 @@ struct VertexInput {
 }
 
 struct VertexOutput {
-	@builtin(position) clip_position: vec4<f32>,
+	@builtin(position) position: vec4<f32>,
 	@location(0) texture_coords: vec2<f32>,
 	@location(1) index: u32,
 }
 
+
+@group(1) @binding(0)
+var<uniform> global: GlobalUniform;
+struct GlobalUniform {
+	camera_position: vec2<f32>,
+	camera_zoom: f32,
+	window_aspect: f32,
+	starfield_texture: u32,
+	starfield_tile_size: f32
+};
+
+
 @vertex
 fn vertex_shader_main(
-	model: VertexInput,
+	vertex: VertexInput,
 	instance: InstanceInput,
 ) -> VertexOutput {
-	let transform_matrix = mat4x4<f32>(
-		instance.transform_matrix_0,
-		instance.transform_matrix_1,
-		instance.transform_matrix_2,
-		instance.transform_matrix_3,
+
+	// Apply sprite aspect ratio & scale factor
+	// This must be done *before* rotation.
+	let scale = instance.height / global.camera_zoom;
+	var pos: vec2<f32> = vec2<f32>(
+		vertex.position.x * instance.aspect * scale,
+		vertex.position.y * scale
+	);
+
+	// Rotate
+	pos = mat2x2<f32>(
+		instance.rotation_matrix_0,
+		instance.rotation_matrix_1,
+	) * pos;
+
+	// Apply screen aspect ratio, again preserving height.
+	// This must be done AFTER rotation... think about it!
+	pos = pos / vec2<f32>(global.window_aspect, 1.0);
+
+	// Translate
+	pos = pos + (
+		// Don't forget to correct distance for screen aspect ratio too!
+		(instance.position / global.camera_zoom)
+		/ vec2<f32>(global.window_aspect, 1.0)
 	);
 
 	var out: VertexOutput;
-	out.texture_coords = model.texture_coords;
-	out.clip_position = transform_matrix * vec4<f32>(model.position, 1.0);
+	out.position = vec4<f32>(pos, 0.0, 1.0);
+	out.texture_coords = vertex.texture_coords;
 	out.index = instance.texture_idx;
 	return out;
 }

src/render/shaders/starfield.wgsl

@@ -1,25 +1,94 @@
 // Vertex shader
 struct InstanceInput {
 	@location(2) position: vec2<f32>,
+	@location(3) parallax: f32,
+	@location(4) height: f32,
 };
 
+struct VertexInput {
+	@location(0) position: vec3<f32>,
+	@location(1) texture_coords: vec2<f32>,
+}
+
 struct VertexOutput {
-	@builtin(position) clip_position: vec4<f32>,
+	@builtin(position) position: vec4<f32>,
+	@location(0) texture_coords: vec2<f32>,
+}
+
+@group(1) @binding(0)
+var<uniform> global: GlobalUniform;
+struct GlobalUniform {
+	camera_position: vec2<f32>,
+	camera_zoom: f32,
+	window_aspect: f32,
+	starfield_texture: u32,
+	starfield_tile_size: f32
+};
+
+
+fn fmod(x: vec2<f32>, m: f32) -> vec2<f32> {
+	return x - floor(x * (1.0 / m)) * m;
 }
 
 @vertex
 fn vertex_shader_main(
+	vertex: VertexInput,
 	instance: InstanceInput,
 ) -> VertexOutput {
-	// Stars consist of only one vertex, so we don't need to pass a buffer into this shader.
-	// We need one instance per star, and that's it!
+
+	// Center of the tile the camera is currently in, in game coordinates.
+	// x div y = x - (x mod y)
+	let tile_center = (
+		global.camera_position
+		- (
+			fmod(
+				global.camera_position + global.starfield_tile_size/2.0,
+				global.starfield_tile_size
+			) - global.starfield_tile_size/2.0
+		)
+	);
+
+	// Apply sprite aspect ratio & scale factor
+	// also applies screen aspect ratio
+	let scale = instance.height / global.camera_zoom;
+	var pos: vec2<f32> = vec2<f32>(
+		vertex.position.x * scale / global.window_aspect,
+		vertex.position.y * scale
+	);
+
+	// 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;
+	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 + parallax_vector) / global.camera_zoom)
+		/ vec2<f32>(global.window_aspect, 1.0)
+	);
+
 	var out: VertexOutput;
-	out.clip_position = vec4<f32>(instance.position, 0.0, 1.0);
+	out.position = vec4<f32>(pos, 0.0, 1.0);
+	out.texture_coords = vertex.texture_coords;
 	return out;
 }
 
+
+@group(0) @binding(0)
+var texture_array: binding_array<texture_2d<f32>>;
+@group(0) @binding(1)
+var sampler_array: binding_array<sampler>;
+
 // Fragment shader
 @fragment
 fn fragment_shader_main(in: VertexOutput) -> @location(0) vec4<f32> {
-	return vec4<f32>(1.0, 1.0, 1.0, 1.0);
+	return textureSampleLevel(
+		texture_array[1],
+		sampler_array[1],
+		in.texture_coords,
+		0.0
+	).rgba * vec4<f32>(0.5, 0.5, 0.5, 1.0);
 }

src/render/util.rs

@@ -1,53 +0,0 @@
-use cgmath::{Deg, Matrix4, Point2, Vector3};
-
-use super::OPENGL_TO_WGPU_MATRIX;
-
-// Represents a sprite tranformation.
-//
-// This produces a single matrix we can apply to a brand-new sprite instance
-// to put it in the right place, at the right angle, with the right scale.
-pub struct Transform {
-	pub pos: Point2<f32>,   // position on screen
-	pub window_aspect: f32, // width / height. Screen aspect ratio.
-	pub sprite_aspect: f32, // width / height. Sprite aspect ratio.
-	pub scale: f32,         // if scale = 1, this sprite will be as tall as the screen.
-	pub rotate: Deg<f32>,   // Around this object's center, in degrees measured ccw from vertical
-}
-
-impl Transform {
-	/// Build the matrix that corresponds to this transformation.
-	pub fn to_matrix(&self) -> Matrix4<f32> {
-		// Note that our mesh starts centered at (0, 0).
-		// This is essential---we do not want scale and rotation
-		// changing our sprite's position!
-
-		// Apply sprite aspect ratio, preserving height.
-		// This must be done *before* rotation.
-		//
-		// We apply the provided scale here as well as a minor optimization
-		let sprite_aspect_and_scale =
-			Matrix4::from_nonuniform_scale(self.sprite_aspect * self.scale, self.scale, 1.0);
-
-		// Apply rotation
-		let rotate = Matrix4::from_angle_z(self.rotate);
-
-		// Apply screen aspect ratio, again preserving height.
-		// This must be done AFTER rotation... think about it!
-		let screen_aspect = Matrix4::from_nonuniform_scale(1.0 / self.window_aspect, 1.0, 1.0);
-
-		// After finishing all op, translate.
-		// This must be done last, all other operations
-		// require us to be at (0, 0).
-		let translate = Matrix4::from_translation(Vector3 {
-			x: self.pos.x,
-			y: self.pos.y,
-			z: 0.0,
-		});
-
-		// Order matters!
-		// The rightmost matrix is applied first.
-		return OPENGL_TO_WGPU_MATRIX
-			* translate * screen_aspect
-			* rotate * sprite_aspect_and_scale;
-	}
-}

src/render/vertexbuffer/types.rs

@@ -32,34 +32,20 @@ impl BufferObject for TexturedVertex {
 	}
 }
 
-// Represents a plain vertex in WGSL
-#[repr(C)]
-#[derive(Copy, Clone, Debug, bytemuck::Pod, bytemuck::Zeroable)]
-pub struct PlainVertex {
-	pub position: [f32; 3],
-}
-
-impl BufferObject for PlainVertex {
-	fn layout() -> wgpu::VertexBufferLayout<'static> {
-		wgpu::VertexBufferLayout {
-			array_stride: Self::SIZE,
-			step_mode: wgpu::VertexStepMode::Vertex,
-			attributes: &[wgpu::VertexAttribute {
-				offset: 0,
-				shader_location: 0,
-				format: wgpu::VertexFormat::Float32x3,
-			}],
-		}
-	}
-}
-
 // Represents a point in the starfield instance in WGSL
 #[repr(C)]
 #[derive(Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
 pub struct StarfieldInstance {
-	// All transformations we need to put this dot in its place
-	// TODO: we don't need that much data
+	/// 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,
+
+	/// Height of (unrotated) sprite in world units
+	pub height: f32,
 }
 
 impl BufferObject for StarfieldInstance {
@@ -67,11 +53,26 @@ impl BufferObject for StarfieldInstance {
 		wgpu::VertexBufferLayout {
 			array_stride: Self::SIZE,
 			step_mode: wgpu::VertexStepMode::Instance,
-			attributes: &[wgpu::VertexAttribute {
-				offset: 0,
-				shader_location: 2,
-				format: wgpu::VertexFormat::Float32x2,
-			}],
+			attributes: &[
+				// Position
+				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,
+				},
+				// Height
+				wgpu::VertexAttribute {
+					offset: mem::size_of::<[f32; 3]>() as wgpu::BufferAddress,
+					shader_location: 4,
+					format: wgpu::VertexFormat::Float32,
+				},
+			],
 		}
 	}
 }
@@ -80,11 +81,19 @@ impl BufferObject for StarfieldInstance {
 #[repr(C)]
 #[derive(Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
 pub struct SpriteInstance {
-	// All transformations we need to put this sprite in its place
-	pub transform: [[f32; 4]; 4],
+	/// Rotation matrix for this sprite
+	pub rotation: [[f32; 2]; 2],
 
-	// Which texture we should use for this sprite
-	// (see TextureArray)
+	/// World position, relative to camera
+	pub position: [f32; 2],
+
+	/// Height of (unrotated) sprite in world units
+	pub height: f32,
+
+	// Sprite aspect ratio (width / height)
+	pub aspect: f32,
+
+	// What texture to use for this sprite
 	pub texture_index: u32,
 }
 
@@ -97,29 +106,39 @@ impl BufferObject for SpriteInstance {
 			// instance when the shader starts processing a new instance
 			step_mode: wgpu::VertexStepMode::Instance,
 			attributes: &[
+				// 2 arrays = 1 2x2 matrix
 				wgpu::VertexAttribute {
 					offset: 0,
 					shader_location: 2,
-					format: wgpu::VertexFormat::Float32x4,
+					format: wgpu::VertexFormat::Float32x2,
 				},
+				wgpu::VertexAttribute {
+					offset: mem::size_of::<[f32; 2]>() as wgpu::BufferAddress,
+					shader_location: 3,
+					format: wgpu::VertexFormat::Float32x2,
+				},
+				// Position
 				wgpu::VertexAttribute {
 					offset: mem::size_of::<[f32; 4]>() as wgpu::BufferAddress,
-					shader_location: 3,
-					format: wgpu::VertexFormat::Float32x4,
+					shader_location: 4,
+					format: wgpu::VertexFormat::Float32x2,
 				},
+				// Height
+				wgpu::VertexAttribute {
+					offset: mem::size_of::<[f32; 6]>() as wgpu::BufferAddress,
+					shader_location: 5,
+					format: wgpu::VertexFormat::Float32,
+				},
+				// Aspect
+				wgpu::VertexAttribute {
+					offset: mem::size_of::<[f32; 7]>() as wgpu::BufferAddress,
+					shader_location: 6,
+					format: wgpu::VertexFormat::Float32,
+				},
+				// Texture
 				wgpu::VertexAttribute {
 					offset: mem::size_of::<[f32; 8]>() as wgpu::BufferAddress,
-					shader_location: 4,
-					format: wgpu::VertexFormat::Float32x4,
-				},
-				wgpu::VertexAttribute {
-					offset: mem::size_of::<[f32; 12]>() as wgpu::BufferAddress,
-					shader_location: 5,
-					format: wgpu::VertexFormat::Float32x4,
-				},
-				wgpu::VertexAttribute {
-					offset: mem::size_of::<[f32; 16]>() as wgpu::BufferAddress,
-					shader_location: 6,
+					shader_location: 7,
 					format: wgpu::VertexFormat::Uint32,
 				},
 			],

src/system.rs

@@ -1,13 +1,37 @@
-use crate::{physics::Polar, Doodad, Sprite, Spriteable};
-use cgmath::Deg;
+use crate::{
+	physics::{Pfloat, Polar},
+	Doodad, Sprite, Spriteable,
+};
+use cgmath::{Deg, Point2};
+use rand::{self, Rng};
+
+pub struct StarfieldStar {
+	// Star coordinates, in world space.
+	// These are relative to the center of a starfield tile.
+	pub pos: Point2<Pfloat>,
+	pub parallax: Pfloat,
+}
 
 pub struct System {
 	bodies: Vec<Doodad>,
+	pub starfield: Vec<StarfieldStar>,
 }
 
 impl System {
 	pub fn new() -> Self {
-		let mut s = System { bodies: Vec::new() };
+		let mut rng = rand::thread_rng();
+		let mut s = System {
+			bodies: Vec::new(),
+			starfield: (0..500)
+				.map(|_| StarfieldStar {
+					pos: Point2 {
+						x: rng.gen_range(-500.0..500.0),
+						y: rng.gen_range(-500.0..500.0),
+					},
+					parallax: rng.gen_range(10.0..11.0),
+				})
+				.collect(),
+		};
 
 		s.bodies.push(Doodad {
 			pos: (0.0, 0.0).into(),