ui hints

.clang-format

@@ -0,0 +1,9 @@
+BasedOnStyle: LLVM
+UseTab: Always
+TabWidth: 4
+IndentWidth: 4
+AccessModifierOffset: -4
+IndentCaseLabels: false
+ColumnLimit: 0
+PointerAlignment: Left
+PackConstructorInitializers: Never

.gitignore

@@ -1 +1,2 @@
 /target
+/build

CMakeLists.txt

@@ -0,0 +1,14 @@
+cmake_minimum_required(VERSION 3.18)
+
+project(photon_light VERSION 1.0.0 LANGUAGES CXX)
+
+set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+
+find_package(Qt6 REQUIRED COMPONENTS Gui Widgets)
+find_program(CARGO cargo REQUIRED)
+set(CARGO_TARGET_DIR "${CMAKE_BINARY_DIR}/cargo")
+
+qt_standard_project_setup()
+
+add_subdirectory(ui)

Cargo.lock

@@ -1165,6 +1165,17 @@ dependencies = [
  "winit",
 ]
 
+[[package]]
+name = "photon-light-impl"
+version = "0.1.0"
+dependencies = [
+ "glam",
+ "photon-light",
+ "pollster",
+ "raw-window-handle",
+ "wgpu",
+]
+
 [[package]]
 name = "pin-project"
 version = "1.1.10"

Cargo.toml

@@ -1,3 +1,6 @@
+[workspace]
+members = ["ui"]
+
 [package]
 name = "photon-light"
 version = "0.1.0"

src/lib.rs

@@ -0,0 +1,401 @@
+#![feature(gen_blocks)]
+
+use std::{convert::identity, error::Error, f32::consts::PI};
+
+use glam::{Mat4, UVec2, Vec2, Vec3, vec3};
+use rand_distr::Distribution as _;
+
+use crate::{
+	camera::OrbitalCamera,
+	ray::Ray,
+	render::lines::{LookParams, Mesh, Pipeline, Vertex},
+	trace::{Hit, Lambertian, Reflector, Scene, Source, Sphere},
+};
+
+mod camera;
+mod ray;
+mod render;
+mod trace;
+
+const OUTPUT_FORMAT: wgpu::TextureFormat = wgpu::TextureFormat::Bgra8UnormSrgb;
+
+#[derive(Debug, Clone, Copy, PartialEq)]
+#[repr(C)]
+pub struct SphericalPosition {
+	pub yaw: f32,
+	pub pitch: f32,
+	pub distance: f32,
+}
+
+#[derive(Debug, Clone, Copy)]
+#[repr(C)]
+pub struct RedrawArgs {
+	pub camera_position: SphericalPosition,
+	pub light_position: SphericalPosition,
+	pub light_radius: f32,
+	pub light_spread: f32,
+	pub accum_sigma: f32,
+	pub accum_scale: f32,
+	pub reflections: u32,
+	pub show_axes: bool,
+	pub show_shapes: bool,
+	pub show_hit_emission: bool,
+	pub show_miss_emission: bool,
+	pub show_direct_hit: bool,
+	pub show_indirect_hit: bool,
+	pub show_light: bool,
+}
+
+pub struct Gpu {
+	device: wgpu::Device,
+	queue: wgpu::Queue,
+	surface: wgpu::Surface<'static>,
+}
+
+pub struct Core {
+	device: wgpu::Device,
+	queue: wgpu::Queue,
+	surface: wgpu::Surface<'static>,
+
+	pipeline: Pipeline,
+	tripod: Mesh,
+}
+
+pub fn new_tripod(device: &wgpu::Device) -> Mesh {
+	Mesh::new(
+		device,
+		&[
+			Vertex::new(vec3(0., 0., 0.), vec3(1., 0., 0.)),
+			Vertex::new(vec3(1., 0., 0.), vec3(1., 0., 0.)),
+			Vertex::new(vec3(0., 0., 0.), vec3(0., 1., 0.)),
+			Vertex::new(vec3(0., 1., 0.), vec3(0., 1., 0.)),
+			Vertex::new(vec3(0., 0., 0.), vec3(0., 0., 1.)),
+			Vertex::new(vec3(0., 0., 1.), vec3(0., 0., 1.)),
+		],
+	)
+}
+
+fn loop_list<T: Clone>(iter: impl IntoIterator<Item = T>) -> impl Iterator<Item = T> {
+	loop_list_ex(iter, identity, identity)
+}
+
+fn loop_list_ex<T: Clone, U>(
+	iter: impl IntoIterator<Item = T>,
+	mut fa: impl FnMut(T) -> U,
+	mut fb: impl FnMut(T) -> U,
+) -> impl Iterator<Item = U> {
+	gen move {
+		let mut iter = iter.into_iter();
+		let Some(first) = iter.next() else { return };
+		yield fa(first.clone());
+		for item in iter {
+			yield fb(item.clone());
+			yield fa(item);
+		}
+		yield fb(first);
+	}
+}
+
+impl OrbitalCamera {
+	fn make_ray(&self, rng: &mut impl rand::Rng) -> Ray {
+		let off: f32 = rand_distr::StandardUniform.sample(rng);
+		let side: Vec2 = rand_distr::UnitCircle.sample(rng).into();
+
+		let m = self.transform().inverse();
+		let fwd = 1. - 0.1 * off;
+		let side_scale = (1. - fwd.powi(2)).sqrt();
+		let dir = Vec3::from((side_scale * side, fwd));
+		Ray {
+			base: self.position(),
+			dir: m.transform_vector3(dir),
+		}
+	}
+}
+
+impl Core {
+	pub fn new(gpu: Gpu) -> Self {
+		let Gpu {
+			device,
+			queue,
+			surface,
+		} = gpu;
+
+		let pipeline = Pipeline::new(&device, OUTPUT_FORMAT);
+		let tripod = new_tripod(&device);
+		queue.submit([]); // flush buffer updates
+
+		Self {
+			device,
+			queue,
+			surface,
+			pipeline,
+			tripod,
+		}
+	}
+
+	fn render(&self, output: &wgpu::Texture, args: &RedrawArgs) {
+		let camera = OrbitalCamera {
+			position_yaw: args.camera_position.yaw,
+			position_pitch: args.camera_position.pitch,
+			distance: args.camera_position.distance,
+		};
+		let aspect = {
+			let size = output.size();
+			let w = size.width as f32;
+			let h = size.height as f32;
+			w / h
+		};
+		let perspective = Mat4::perspective_lh(PI / 3., aspect, 1e-2, 1e2);
+		self.pipeline.set_look(
+			&self.queue,
+			LookParams {
+				m: perspective * camera.transform(),
+			},
+		);
+		self.queue.submit([]); // flush buffer updates
+
+		let view = output.create_view(&wgpu::TextureViewDescriptor::default());
+		let mut encoder = self
+			.device
+			.create_command_encoder(&wgpu::CommandEncoderDescriptor::default());
+		let mut pass = encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
+			color_attachments: &[Some(wgpu::RenderPassColorAttachment {
+				view: &view,
+				depth_slice: None,
+				resolve_target: None,
+				ops: wgpu::Operations {
+					load: wgpu::LoadOp::Clear(wgpu::Color::BLACK),
+					store: wgpu::StoreOp::Store,
+				},
+			})],
+			depth_stencil_attachment: None,
+			..Default::default()
+		});
+		if args.show_axes {
+			self.pipeline.render(&mut pass, [&self.tripod]);
+		}
+
+		let source = Source {
+			position_yaw: args.light_position.yaw,
+			position_pitch: args.light_position.pitch,
+			distance: args.light_position.distance,
+			radius: args.light_radius,
+			spread: args.light_spread,
+		};
+
+		if args.show_shapes {
+			let contour: Vec<Vertex> = loop_list(source.contour(17))
+				.map(|pos| Vertex {
+					pos,
+					color: vec3(1., 1., 1.),
+				})
+				.collect();
+			self.pipeline
+				.render(&mut pass, [&Mesh::new(&self.device, &contour)]);
+		}
+
+		const BASE_R: f32 = 2.;
+		const BASE_POS: Vec3 = vec3(0., 0., -BASE_R);
+		const BASE: Sphere = Sphere {
+			position: vec3(0., 0., -BASE_R),
+			radius: BASE_R,
+		};
+		fn sphere(pos: Vec3) -> Sphere {
+			Sphere {
+				position: pos,
+				radius: BASE_POS.distance(pos) - BASE_R,
+			}
+		}
+		let scene = Scene {
+			objects: vec![
+				BASE,
+				sphere(vec3(0., 0., 0.1)),
+				sphere(vec3(0.3, 0., 0.1)),
+				sphere(vec3(0.1, 0.3, 0.1)),
+			],
+		};
+
+		let mut prng = rand_pcg::Pcg64::new(42, 0);
+		let source_rays: Vec<Ray> = (0..10240).map(|_| source.make_ray(&mut prng)).collect();
+		let camera_rays: Vec<Ray> = (0..10240).map(|_| camera.make_ray(&mut prng)).collect();
+		let mut source_ray_display: Vec<Vertex> = Vec::with_capacity(source_rays.len());
+		let mut hits: Vec<Hit> = Vec::with_capacity(source_rays.len());
+		for ray in source_rays {
+			if let Some(hit) = scene.trace_ray(ray) {
+				hits.push(hit);
+				if args.show_hit_emission {
+					source_ray_display.extend([
+						Vertex {
+							pos: ray.base,
+							color: vec3(1., 1., 1.),
+						},
+						Vertex {
+							pos: ray.base + 0.1 * ray.dir,
+							color: vec3(0., 1., 0.),
+						},
+					]);
+				}
+				if args.show_direct_hit {
+					source_ray_display.extend([
+						Vertex {
+							pos: hit.incident.base - 0.02 * hit.incident.dir,
+							color: vec3(0., 0., 1.),
+						},
+						Vertex {
+							pos: hit.incident.base,
+							color: vec3(1., 1., 1.),
+						},
+					]);
+				}
+			} else {
+				if args.show_miss_emission {
+					source_ray_display.extend([
+						Vertex {
+							pos: ray.base,
+							color: vec3(1., 1., 1.),
+						},
+						Vertex {
+							pos: ray.base + 0.1 * ray.dir,
+							color: vec3(1., 0., 0.),
+						},
+					]);
+				}
+			}
+		}
+		if args.reflections > 0 {
+			let mut hits1 = hits.clone();
+			for _ in 0..args.reflections {
+				let mut hits2: Vec<Hit> = Vec::with_capacity(hits1.len());
+				for hit in &hits1 {
+					let reflector = Lambertian;
+					let reflected = reflector.reflect(&mut prng, hit.normal, hit.incident.dir);
+					let ray = Ray::new(hit.incident.base, reflected);
+					let Some(hit2) = scene.trace_ray(ray) else {
+						continue;
+					};
+					hits2.push(hit2);
+					if args.show_indirect_hit {
+						source_ray_display.extend([
+							Vertex {
+								pos: hit2.incident.base - 0.02 * hit2.incident.dir,
+								color: vec3(1., 0., 1.),
+							},
+							Vertex {
+								pos: hit2.incident.base,
+								color: vec3(1., 1., 1.),
+							},
+						]);
+					}
+				}
+				hits.extend(&hits2);
+				hits1 = hits2;
+			}
+		}
+		let mut camera_ray_display: Vec<Vertex> = Vec::with_capacity(camera_rays.len());
+		if args.show_light {
+			let sigma2 = args.accum_sigma.powi(2);
+			let accum_normalizator = (2. * PI * sigma2).sqrt().recip();
+			for ray in camera_rays {
+				let Some(hit) = scene.trace_ray(ray) else {
+					continue;
+				};
+				let mut total_cd = 0.0f32;
+				for light_hit in &hits {
+					let d2 = hit.incident.base.distance_squared(light_hit.incident.base);
+					if d2 > 9. * sigma2 {
+						continue;
+					}
+					assert!(hit.normal.is_normalized());
+					assert!(hit.incident.dir.is_normalized());
+					let reflector = Lambertian;
+					let in_lm = 1.0;
+					let out_cd = in_lm
+						* hit.normal.dot(-hit.incident.dir)
+						* reflector.brdf(hit.normal, hit.incident.dir, -ray.dir);
+					let weight = accum_normalizator * (-0.5 * d2 / sigma2).exp();
+					total_cd += weight * out_cd;
+				}
+				let brightness = 3. * (1. - (1. + total_cd * args.accum_scale).recip());
+				let r = args.accum_sigma;
+				let color = vec3(brightness, brightness - 1., brightness - 2.)
+					.clamp(Vec3::splat(0.), Vec3::splat(1.));
+				let vertex = |off: Vec3| Vertex {
+					pos: hit.incident.base + r * off,
+					color,
+				};
+				camera_ray_display.extend([
+					vertex(-Vec3::X),
+					vertex(Vec3::X),
+					vertex(-Vec3::Y),
+					vertex(Vec3::Y),
+					vertex(-Vec3::Z),
+					vertex(Vec3::Z),
+				]);
+			}
+		}
+		if !source_ray_display.is_empty() {
+			self.pipeline
+				.render(&mut pass, [&Mesh::new(&self.device, &source_ray_display)]);
+		}
+		if !camera_ray_display.is_empty() {
+			self.pipeline
+				.render(&mut pass, [&Mesh::new(&self.device, &camera_ray_display)]);
+		}
+
+		drop(pass);
+		self.queue.submit(std::iter::once(encoder.finish()));
+	}
+
+	/// Configures the renderer for a given target size.
+	pub fn configure(&mut self, pixel_size: UVec2) {
+		self.surface.configure(
+			&self.device,
+			&wgpu::SurfaceConfiguration {
+				usage: wgpu::TextureUsages::RENDER_ATTACHMENT | wgpu::TextureUsages::COPY_DST,
+				format: OUTPUT_FORMAT,
+				width: pixel_size.x,
+				height: pixel_size.y,
+				present_mode: wgpu::PresentMode::Fifo,
+				alpha_mode: wgpu::CompositeAlphaMode::Auto,
+				view_formats: vec![],
+				desired_maximum_frame_latency: 2,
+			},
+		);
+	}
+
+	/// Redraws the entire surface.
+	///
+	/// [`Self::configure`] must be called at least once before this.
+	pub fn redraw(&mut self, args: &RedrawArgs) {
+		let output = self.surface.get_current_texture().unwrap();
+		self.render(&output.texture, args);
+		output.present();
+	}
+}
+
+pub async fn init_gpu_inner<E: Error + 'static>(
+	make_surface: impl FnOnce(&wgpu::Instance) -> Result<wgpu::Surface<'static>, E>,
+) -> Result<Gpu, Box<dyn Error>> {
+	let instance = wgpu::Instance::new(&wgpu::InstanceDescriptor {
+		backends: wgpu::Backends::PRIMARY,
+		..Default::default()
+	});
+	let surface = make_surface(&instance)?;
+	let adapter = instance
+		.request_adapter(&wgpu::RequestAdapterOptions {
+			power_preference: wgpu::PowerPreference::default(),
+			compatible_surface: Some(&surface),
+			force_fallback_adapter: false,
+		})
+		.await
+		.unwrap();
+	let (device, queue) = adapter
+		.request_device(&wgpu::DeviceDescriptor::default())
+		.await
+		.unwrap();
+	Ok(Gpu {
+		device,
+		queue,
+		surface,
+	})
+}

src/main.rs

@@ -1,8 +1,7 @@
-#![feature(gen_blocks)]
+use std::{f32::consts::PI, sync::Arc};
 
-use std::{convert::identity, error::Error, f32::consts::PI, sync::Arc};
-
-use glam::{Mat4, Vec3, vec3};
+use glam::uvec2;
+use photon_light::{Core, RedrawArgs, SphericalPosition, init_gpu_inner};
 use winit::{
 	application::ApplicationHandler,
 	event::WindowEvent,
@@ -10,236 +9,58 @@ use winit::{
 	window::Window,
 };
 
-use crate::{
-	camera::OrbitalCamera,
-	render::lines::{LookParams, Mesh, Pipeline, Vertex},
-	trace::{Scene, Source, Sphere},
-};
-
-mod camera;
-mod ray;
-mod render;
-mod trace;
-
 const TITLE: &str = "WGPU example";
-const OUTPUT_FORMAT: wgpu::TextureFormat = wgpu::TextureFormat::Bgra8UnormSrgb;
 
 struct MainWindow {
-	handle: Arc<Window>,
-	device: wgpu::Device,
-	queue: wgpu::Queue,
-	surface: wgpu::Surface<'static>,
-	surface_configured: bool,
-
-	pipeline: Pipeline,
-	tripod: Mesh,
-}
-
-pub fn new_tripod(device: &wgpu::Device) -> Mesh {
-	Mesh::new(
-		device,
-		&[
-			Vertex::new(vec3(0., 0., 0.), vec3(1., 0., 0.)),
-			Vertex::new(vec3(1., 0., 0.), vec3(1., 0., 0.)),
-			Vertex::new(vec3(0., 0., 0.), vec3(0., 1., 0.)),
-			Vertex::new(vec3(0., 1., 0.), vec3(0., 1., 0.)),
-			Vertex::new(vec3(0., 0., 0.), vec3(0., 0., 1.)),
-			Vertex::new(vec3(0., 0., 1.), vec3(0., 0., 1.)),
-		],
-	)
-}
-
-fn loop_list<T: Clone>(iter: impl IntoIterator<Item = T>) -> impl Iterator<Item = T> {
-	loop_list_ex(iter, identity, identity)
-}
-
-fn loop_list_ex<T: Clone, U>(
-	iter: impl IntoIterator<Item = T>,
-	mut fa: impl FnMut(T) -> U,
-	mut fb: impl FnMut(T) -> U,
-) -> impl Iterator<Item = U> {
-	gen move {
-		let mut iter = iter.into_iter();
-		let Some(first) = iter.next() else { return };
-		yield fa(first.clone());
-		for item in iter {
-			yield fb(item.clone());
-			yield fa(item);
-		}
-		yield fb(first);
-	}
+	window: Arc<Window>,
+	core: Core,
 }
 
 impl MainWindow {
 	fn new(event_loop: &ActiveEventLoop) -> Self {
-		let handle = event_loop
+		let window = event_loop
 			.create_window(Window::default_attributes().with_title(TITLE))
 			.unwrap();
-		let handle = Arc::new(handle);
-
-		let (device, queue, surface) = pollster::block_on(init_gpu(Arc::clone(&handle))).unwrap();
-		let pipeline = Pipeline::new(&device, OUTPUT_FORMAT);
-		let tripod = new_tripod(&device);
-		queue.submit([]); // flush buffer updates
-
-		Self {
-			handle,
-			device,
-			queue,
-			surface,
-			surface_configured: false,
-			pipeline,
-			tripod,
-		}
-	}
-
-	fn render(&self, output: &wgpu::Texture) {
-		let camera = OrbitalCamera {
-			position_yaw: PI / 4.,
-			position_pitch: 0.5f32.sqrt().atan(),
-			distance: 3.0,
-		};
-		let aspect = {
-			let size = output.size();
-			let w = size.width as f32;
-			let h = size.height as f32;
-			w / h
-		};
-		let perspective = Mat4::perspective_lh(PI / 3., aspect, 1e-2, 1e2);
-		self.pipeline.set_look(
-			&self.queue,
-			LookParams {
-				m: perspective * camera.transform(),
-			},
-		);
-		self.queue.submit([]); // flush buffer updates
-
-		let view = output.create_view(&wgpu::TextureViewDescriptor::default());
-		let mut encoder = self
-			.device
-			.create_command_encoder(&wgpu::CommandEncoderDescriptor::default());
-		let mut pass = encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
-			color_attachments: &[Some(wgpu::RenderPassColorAttachment {
-				view: &view,
-				depth_slice: None,
-				resolve_target: None,
-				ops: wgpu::Operations {
-					load: wgpu::LoadOp::Clear(wgpu::Color {
-						r: 0.1,
-						g: 0.2,
-						b: 0.8,
-						a: 1.0,
-					}),
-					store: wgpu::StoreOp::Store,
-				},
-			})],
-			depth_stencil_attachment: None,
-			..Default::default()
-		});
-		self.pipeline.render(&mut pass, [&self.tripod]);
-
-		let source = Source {
-			position_yaw: 0.0,
-			position_pitch: PI / 3.,
-			distance: 1.0,
-			radius: 0.125,
-			spread: 0.125,
-		};
-
-		let contour: Vec<Vertex> = loop_list(source.contour(17))
-			.map(|pos| Vertex {
-				pos,
-				color: vec3(1., 1., 1.),
-			})
-			.collect();
-		self.pipeline
-			.render(&mut pass, [&Mesh::new(&self.device, &contour)]);
-
-		const BASE_R: f32 = 2.;
-		const BASE_POS: Vec3 = vec3(0., 0., -BASE_R);
-		const BASE: Sphere = Sphere {
-			position: vec3(0., 0., -BASE_R),
-			radius: BASE_R,
-		};
-		fn sphere(pos: Vec3) -> Sphere {
-			Sphere {
-				position: pos,
-				radius: BASE_POS.distance(pos) - BASE_R,
-			}
-		}
-		let scene = Scene {
-			objects: vec![
-				BASE,
-				sphere(vec3(0., 0., 0.1)),
-				sphere(vec3(0.3, 0., 0.1)),
-				sphere(vec3(0.1, 0.3, 0.1)),
-			],
-		};
-
-		let mut prng = rand_pcg::Pcg64::new(42, 0);
-		let rays: Vec<Vertex> = (0..10000)
-			.flat_map(|_| {
-				let ray = source.make_ray(&mut prng);
-				if let Some(ray) = scene.trace_ray(ray) {
-					[
-						Vertex {
-							pos: ray.base - 0.02 * ray.dir,
-							color: vec3(1., 1., 1.),
-						},
-						Vertex {
-							pos: ray.base,
-							color: vec3(0., 1., 0.),
-						},
-					]
-				} else {
-					[
-						Vertex {
-							pos: ray.base,
-							color: vec3(1., 1., 1.),
-						},
-						Vertex {
-							pos: ray.base + 0.1 * ray.dir,
-							color: vec3(1., 0., 0.),
-						},
-					]
-				}
-			})
-			.collect();
-		self.pipeline
-			.render(&mut pass, [&Mesh::new(&self.device, &rays)]);
-
-		drop(pass);
-		self.queue.submit(std::iter::once(encoder.finish()));
+		let window = Arc::new(window);
+		let gpu = pollster::block_on(init_gpu_inner(|instance| {
+			instance.create_surface(Arc::clone(&window))
+		}))
+		.unwrap();
+		let mut core = Core::new(gpu);
+		core.configure(uvec2(1, 1));
+		Self { window, core }
 	}
 
 	fn event(&mut self, event_loop: &ActiveEventLoop, event: WindowEvent) {
 		match event {
 			WindowEvent::CloseRequested => event_loop.exit(),
-			WindowEvent::Resized(physical_size) => {
-				self.surface.configure(
-					&self.device,
-					&wgpu::SurfaceConfiguration {
-						usage: wgpu::TextureUsages::RENDER_ATTACHMENT
-							| wgpu::TextureUsages::COPY_DST,
-						format: OUTPUT_FORMAT,
-						width: physical_size.width,
-						height: physical_size.height,
-						present_mode: wgpu::PresentMode::Fifo,
-						alpha_mode: wgpu::CompositeAlphaMode::Auto,
-						view_formats: vec![],
-						desired_maximum_frame_latency: 2,
+			WindowEvent::Resized(physical_size) => self
+				.core
+				.configure(uvec2(physical_size.width, physical_size.height)),
+			WindowEvent::RedrawRequested => self.core.redraw(&RedrawArgs {
+				camera_position: SphericalPosition {
+					yaw: PI / 4.,
+					pitch: 0.5f32.sqrt().atan(),
+					distance: 3.0,
 				},
-				);
-				self.surface_configured = true;
-			}
-			WindowEvent::RedrawRequested => {
-				if !self.surface_configured {
-					return;
-				}
-				let output = self.surface.get_current_texture().unwrap();
-				self.render(&output.texture);
-				output.present();
-			}
+				light_position: SphericalPosition {
+					yaw: 0.0,
+					pitch: PI / 3.,
+					distance: 1.0,
+				},
+				light_radius: 0.125,
+				light_spread: 0.125,
+				accum_sigma: 0.025,
+				accum_scale: 0.01,
+				reflections: 2,
+				show_axes: true,
+				show_shapes: true,
+				show_hit_emission: false,
+				show_miss_emission: false,
+				show_direct_hit: false,
+				show_indirect_hit: false,
+				show_light: true,
+			}),
 			_ => {}
 		}
 	}
@@ -270,34 +91,11 @@ impl ApplicationHandler for Application {
 			.main_window
 			.as_mut()
 			.expect("window must exist to recieve events");
-		assert_eq!(window.handle.id(), window_id);
+		assert_eq!(window.window.id(), window_id);
 		window.event(event_loop, event);
 	}
 }
 
-async fn init_gpu<'window>(
-	wnd: impl wgpu::WindowHandle + 'window,
-) -> Result<(wgpu::Device, wgpu::Queue, wgpu::Surface<'window>), Box<dyn Error>> {
-	let instance = wgpu::Instance::new(&wgpu::InstanceDescriptor {
-		backends: wgpu::Backends::PRIMARY,
-		..Default::default()
-	});
-	let surface = instance.create_surface(wnd)?;
-	let adapter = instance
-		.request_adapter(&wgpu::RequestAdapterOptions {
-			power_preference: wgpu::PowerPreference::default(),
-			compatible_surface: Some(&surface),
-			force_fallback_adapter: false,
-		})
-		.await
-		.unwrap();
-	let (device, queue) = adapter
-		.request_device(&wgpu::DeviceDescriptor::default())
-		.await
-		.unwrap();
-	Ok((device, queue, surface))
-}
-
 fn main() {
 	let event_loop = EventLoop::new().unwrap();
 	event_loop.set_control_flow(ControlFlow::Wait);

src/trace.rs

@@ -1,7 +1,7 @@
 use std::f32::consts::PI;
 
 use glam::{Mat4, Vec2, Vec3, vec3};
-use rand_distr::Distribution;
+use rand_distr::{Distribution, UnitSphere};
 
 use crate::{camera::OrbitalCamera, ray::Ray};
 
@@ -78,8 +78,14 @@ pub struct Sphere {
 	pub radius: f32,
 }
 
+struct Hit1 {
+	pos: Vec3,
+	dist: f32,
+	normal: Vec3,
+}
+
 impl Sphere {
-	fn trace_ray(&self, ray: Ray) -> Option<f32> {
+	fn trace_ray(&self, ray: Ray) -> Option<Hit1> {
 		// let t: f32;
 		// let hit = ray.base + t * ray.dir;
 		// (hit - self.position).length() == self.radius;
@@ -94,7 +100,10 @@ impl Sphere {
 		if d4 < 0. {
 			return None;
 		}
-		Some((-b2 - d4.sqrt()) / a)
+		let dist = (-b2 - d4.sqrt()) / a;
+		let pos = ray.advance(dist).base;
+		let normal = (pos - self.position).normalize();
+		Some(Hit1 { pos, dist, normal })
 	}
 }
 
@@ -103,13 +112,51 @@ pub struct Scene {
 	pub objects: Vec<Sphere>,
 }
 
+#[derive(Debug, Clone, Copy)]
+pub struct Hit {
+	pub incident: Ray,
+	pub normal: Vec3,
+}
+
 impl Scene {
-	pub fn trace_ray(&self, ray: Ray) -> Option<Ray> {
-		let dist = self
+	pub fn trace_ray(&self, ray: Ray) -> Option<Hit> {
+		const EPS: f32 = -1e-3;
+		let hit = self
 			.objects
 			.iter()
 			.filter_map(|obj| obj.trace_ray(ray))
-			.min_by(f32::total_cmp);
-		Some(ray.advance(dist?))
+			.filter(|h| h.dist >= EPS)
+			.min_by(|a, b| f32::total_cmp(&a.dist, &b.dist))?;
+		Some(Hit {
+			incident: Ray {
+				base: hit.pos,
+				dir: ray.dir,
+			},
+			normal: hit.normal,
+		})
+	}
+}
+
+pub trait Reflector {
+	fn brdf(&self, normal: Vec3, incident: Vec3, reflected: Vec3) -> f32 /* 1/sr */;
+	fn reflect(&self, rgen: &mut impl rand::Rng, normal: Vec3, incident: Vec3) -> Vec3;
+}
+
+pub struct Lambertian;
+
+impl Reflector for Lambertian {
+	fn brdf(&self, _normal: Vec3, _incident: Vec3, _reflected: Vec3) -> f32 {
+		1. / PI
+	}
+
+	fn reflect(&self, rgen: &mut impl rand::Rng, normal: Vec3, _incident: Vec3) -> Vec3 {
+		let sphere: Vec3 = UnitSphere.sample(rgen).into();
+		let sphere_n = normal.dot(sphere); // uniform on [-1, 1]!
+		let sphere_t = sphere - sphere_n * normal;
+
+		let out_n_len2 = sphere_n.abs();
+		let out_t = (1. + out_n_len2).recip().sqrt() * sphere_t;
+		let out_n = out_n_len2.sqrt() * normal;
+		out_t + out_n
 	}
 }

ui/CMakeLists.txt

@@ -0,0 +1,13 @@
+include(impl.cmake)
+
+qt_add_executable(photon_light
+	src/api.cxx
+	src/main.cxx
+	src/main_window.cxx
+	src/main_window.ui
+	src/viewport.cxx
+)
+
+target_link_libraries(photon_light PRIVATE Qt6::Gui Qt6::Widgets)
+target_link_libraries(photon_light PRIVATE photon_light_impl)
+target_include_directories(photon_light PRIVATE src)

ui/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "photon-light-impl"
+version = "0.1.0"
+edition = "2024"
+
+[lib]
+crate-type = ["staticlib"]
+
+[dependencies]
+photon-light = {path = "../"}
+
+glam = { version = "0.30" }
+pollster = "0.4.0"
+raw-window-handle = "0.6.2"
+wgpu = "27.0.1"

ui/impl.cmake

@@ -0,0 +1,22 @@
+set(impl_basename "${CARGO_TARGET_DIR}/release/libphoton_light_impl")
+
+add_custom_command(
+	OUTPUT ${impl_basename}.a
+	COMMAND env CARGO_TARGET_DIR=${CARGO_TARGET_DIR} ${CARGO} build --release --package photon-light-impl
+	WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
+	DEPFILE ${impl_basename}.d
+	USES_TERMINAL
+	JOB_SERVER_AWARE
+	DEPENDS_EXPLICIT_ONLY
+)
+
+# HACK ensure CMake *actually adds* the command above
+add_custom_target(build_impl
+	DEPENDS ${impl_basename}.a
+)
+
+add_library(photon_light_impl STATIC IMPORTED)
+
+set_target_properties(photon_light_impl PROPERTIES
+	IMPORTED_LOCATION ${impl_basename}.a
+)

ui/src/api.cxx

@@ -0,0 +1,57 @@
+#include "api.hxx"
+
+#include <stdexcept>
+#include <utility>
+
+namespace ffi {
+extern "C" Core* rt4_viewport_create(xcb_connection_t* connection, std::uint32_t window);
+extern "C" void rt4_viewport_destroy(Core* viewport);
+extern "C" void rt4_viewport_configure(Core* viewport, std::uint32_t width, std::uint32_t height);
+extern "C" void rt4_viewport_redraw(Core* viewport, const RedrawArgs* args);
+} // namespace ffi
+
+BoxCore::BoxCore(BoxCore&& b)
+	: ptr(std::exchange(b.ptr, {})) {
+}
+
+BoxCore::~BoxCore() {
+	reset();
+}
+
+BoxCore& BoxCore::operator=(BoxCore&& b) {
+	if (&b == this)
+		return *this;
+	std::swap(ptr, b.ptr);
+	b.reset();
+	return *this;
+}
+
+BoxCore BoxCore::from_xcb(xcb_connection_t* connection, std::uint32_t window) {
+	if (!connection)
+		throw std::logic_error("attempt to use a null connection");
+	if (!window)
+		throw std::logic_error("attempt to use a null window");
+	BoxCore out;
+	out.ptr.ptr = ffi::rt4_viewport_create(connection, window);
+	return out;
+}
+
+void BoxCore::reset() {
+	auto viewport = std::exchange(ptr, {});
+	if (viewport)
+		ffi::rt4_viewport_destroy(viewport.use());
+}
+
+ffi::Core* MutCore::use() const {
+	if (!ptr)
+		throw std::logic_error("attempt to use a null Core");
+	return ptr;
+}
+
+void MutCore::configure(std::uint32_t width, std::uint32_t height) const {
+	rt4_viewport_configure(use(), width, height);
+}
+
+void MutCore::redraw(const RedrawArgs& args) const {
+	rt4_viewport_redraw(use(), &args);
+}

ui/src/api.hxx

@@ -0,0 +1,69 @@
+#pragma once
+
+#include <cstdint>
+
+struct xcb_connection_t;
+
+namespace ffi {
+struct Core;
+
+struct SphericalPosition {
+	float yaw = 0.;
+	float pitch = 0.;
+	float distance = 1.;
+};
+
+struct RedrawArgs {
+	SphericalPosition camera_position;
+	SphericalPosition light_position;
+	float light_radius = 1.;
+	float light_spread = 0.;
+	float accum_sigma = 1.;
+	float accum_scale = 1.;
+	std::uint32_t reflections = 0;
+	bool show_axes = true;
+	bool show_shapes = true;
+	bool show_hit_emission = true;
+	bool show_miss_emission = true;
+	bool show_direct_hit = true;
+	bool show_indirect_hit = true;
+	bool show_light = true;
+};
+} // namespace ffi
+
+using ffi::RedrawArgs;
+using ffi::SphericalPosition;
+
+class MutCore {
+	friend class BoxCore;
+
+public:
+	explicit operator bool() const { return ptr; }
+
+	void configure(std::uint32_t width, std::uint32_t height) const;
+	void redraw(const RedrawArgs& args) const;
+
+private:
+	ffi::Core* ptr = nullptr;
+	ffi::Core* use() const;
+};
+
+class BoxCore {
+public:
+	BoxCore() = default;
+	BoxCore(const BoxCore&) = delete;
+	BoxCore(BoxCore&&);
+	BoxCore& operator=(const BoxCore&) = delete;
+	BoxCore& operator=(BoxCore&&);
+	~BoxCore();
+
+	explicit operator bool() const { return !!ptr; }
+	const MutCore* operator->() const { return &ptr; }
+
+	void reset();
+
+	static BoxCore from_xcb(xcb_connection_t* connection, std::uint32_t window);
+
+private:
+	MutCore ptr;
+};

ui/src/lib.rs

@@ -0,0 +1,45 @@
+use std::{ffi::c_void, num::NonZero, ptr::NonNull};
+
+use glam::uvec2;
+use photon_light::{Core, RedrawArgs, init_gpu_inner};
+use raw_window_handle::{RawDisplayHandle, RawWindowHandle, XcbDisplayHandle, XcbWindowHandle};
+
+unsafe fn create_viewport(
+	display: impl Into<RawDisplayHandle>,
+	window: impl Into<RawWindowHandle>,
+) -> Box<Core> {
+	let target = wgpu::SurfaceTargetUnsafe::RawHandle {
+		raw_display_handle: display.into(),
+		raw_window_handle: window.into(),
+	};
+	let gpu = pollster::block_on(init_gpu_inner(|instance| unsafe {
+		instance.create_surface_unsafe(target)
+	}))
+	.unwrap();
+	Box::new(Core::new(gpu))
+}
+
+#[unsafe(no_mangle)]
+unsafe extern "C" fn rt4_viewport_create(
+	connection: NonNull<c_void>,
+	window: NonZero<u32>,
+) -> Box<Core> {
+	let display = XcbDisplayHandle::new(Some(connection), 0);
+	let window = XcbWindowHandle::new(window);
+	unsafe { create_viewport(display, window) }
+}
+
+#[unsafe(no_mangle)]
+unsafe extern "C" fn rt4_viewport_destroy(viewport: Box<Core>) {
+	drop(viewport);
+}
+
+#[unsafe(no_mangle)]
+unsafe extern "C" fn rt4_viewport_configure(viewport: &mut Core, width: u32, height: u32) {
+	viewport.configure(uvec2(width, height));
+}
+
+#[unsafe(no_mangle)]
+unsafe extern "C" fn rt4_viewport_redraw(viewport: &mut Core, args: &RedrawArgs) {
+	viewport.redraw(args);
+}

ui/src/main.cxx

@@ -0,0 +1,12 @@
+#include "main_window.hxx"
+
+#include <QApplication>
+
+int main(int argc, char* argv[]) {
+	QApplication app(argc, argv);
+
+	auto w = new PhotonLight;
+	w->show();
+
+	return app.exec();
+}

ui/src/main_window.cxx

@@ -0,0 +1,54 @@
+#include "main_window.hxx"
+
+#include "ui_main_window.h"
+
+PhotonLight::PhotonLight(QWidget* parent)
+	: QMainWindow(parent),
+	  m_ui(new Ui::MainWindow) {
+	m_ui->setupUi(this);
+	updateView();
+}
+
+PhotonLight::~PhotonLight() = default;
+
+float deg_to_rad(float val) {
+	return val * float(M_PI / 180);
+}
+
+void PhotonLight::updateView() {
+	RedrawArgs args{
+		.camera_position = SphericalPosition{
+			.yaw = deg_to_rad(m_ui->cameraYaw->value()),
+			.pitch = deg_to_rad(m_ui->cameraPitch->value()),
+			.distance = m_ui->cameraDistance->value() / 10.0f,
+		},
+		.light_position = SphericalPosition{
+			.yaw = deg_to_rad(m_ui->lightYaw->value()),
+			.pitch = deg_to_rad(m_ui->lightPitch->value()),
+			.distance = m_ui->lightDistance->value() / 10.0f,
+		},
+		.light_radius = 0.125,
+		.light_spread = 0.125,
+		.accum_sigma = exp10f(m_ui->accumSigma->value() / 25.0),
+		.accum_scale = exp10f(m_ui->accumScale->value() / 25.0),
+		.reflections = std::uint32_t(m_ui->reflections->value()),
+		.show_axes = m_ui->displayAxes->isChecked(),
+		.show_shapes = m_ui->displayShapes->isChecked(),
+		.show_hit_emission = m_ui->displayEmitted->isChecked(),
+		.show_miss_emission = m_ui->displayEmitted->isChecked(),
+		.show_direct_hit = m_ui->displayDirectHits->isChecked(),
+		.show_indirect_hit = m_ui->displayIndirectHits->isChecked(),
+		.show_light = m_ui->displayResult->isChecked(),
+	};
+	m_ui->cameraYawLabel->setText(tr("Yaw: %1 deg").arg(QString::number(qRadiansToDegrees(args.camera_position.yaw))));
+	m_ui->cameraPitchLabel->setText(tr("Pitch: %1 deg").arg(QString::number(qRadiansToDegrees(args.camera_position.pitch))));
+	m_ui->cameraDistanceLabel->setText(tr("Distance: %1").arg(QString::number(args.camera_position.distance)));
+	m_ui->lightYawLabel->setText(tr("Yaw: %1 deg").arg(QString::number(qRadiansToDegrees(args.light_position.yaw))));
+	m_ui->lightPitchLabel->setText(tr("Pitch: %1 deg").arg(QString::number(qRadiansToDegrees(args.light_position.pitch))));
+	m_ui->lightDistanceLabel->setText(tr("Distance: %1").arg(QString::number(args.light_position.distance)));
+	m_ui->accumSigmaLabel->setText(tr("Averaging radius: %1").arg(QString::number(args.accum_sigma, 'f', 3)));
+	m_ui->accumScaleLabel->setText(tr("Brightness: %1").arg(QString::number(args.accum_scale, 'f', 3)));
+	m_ui->viewport->setView(args);
+}
+
+#include "moc_main_window.cpp"

ui/src/main_window.hxx

@@ -0,0 +1,22 @@
+#pragma once
+#include <QMainWindow>
+
+#include <memory>
+
+namespace Ui {
+class MainWindow;
+}
+
+class PhotonLight : public QMainWindow {
+	Q_OBJECT
+
+public:
+	explicit PhotonLight(QWidget* parent = nullptr);
+	~PhotonLight() override;
+
+public slots:
+	void updateView();
+
+private:
+	const std::unique_ptr<Ui::MainWindow> m_ui;
+};

ui/src/main_window.ui

@@ -0,0 +1,644 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ui version="4.0">
+ <class>MainWindow</class>
+ <widget class="QMainWindow" name="MainWindow">
+  <property name="geometry">
+   <rect>
+    <x>0</x>
+    <y>0</y>
+    <width>1600</width>
+    <height>1200</height>
+   </rect>
+  </property>
+  <property name="windowTitle">
+   <string>MainWindow</string>
+  </property>
+  <widget class="QWidget" name="centralwidget">
+   <layout class="QHBoxLayout" name="horizontalLayout_2">
+    <item>
+     <widget class="Viewport" name="viewport" native="true"/>
+    </item>
+   </layout>
+  </widget>
+  <widget class="QMenuBar" name="menubar">
+   <property name="geometry">
+    <rect>
+     <x>0</x>
+     <y>0</y>
+     <width>1600</width>
+     <height>38</height>
+    </rect>
+   </property>
+  </widget>
+  <widget class="QStatusBar" name="statusbar"/>
+  <widget class="QDockWidget" name="dockWidget">
+   <property name="features">
+    <set>QDockWidget::DockWidgetFloatable|QDockWidget::DockWidgetMovable</set>
+   </property>
+   <attribute name="dockWidgetArea">
+    <number>2</number>
+   </attribute>
+   <widget class="QWidget" name="dockWidgetContents">
+    <layout class="QVBoxLayout" name="verticalLayout_2">
+     <item>
+      <widget class="QGroupBox" name="groupBox">
+       <property name="title">
+        <string>Camera</string>
+       </property>
+       <layout class="QVBoxLayout" name="verticalLayout">
+        <item>
+         <widget class="QLabel" name="cameraYawLabel">
+          <property name="text">
+           <string>Yaw</string>
+          </property>
+          <property name="buddy">
+           <cstring>cameraYaw</cstring>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QSlider" name="cameraYaw">
+          <property name="minimum">
+           <number>-180</number>
+          </property>
+          <property name="maximum">
+           <number>180</number>
+          </property>
+          <property name="pageStep">
+           <number>15</number>
+          </property>
+          <property name="value">
+           <number>45</number>
+          </property>
+          <property name="orientation">
+           <enum>Qt::Horizontal</enum>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QLabel" name="cameraPitchLabel">
+          <property name="text">
+           <string>Pitch</string>
+          </property>
+          <property name="buddy">
+           <cstring>cameraPitch</cstring>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QSlider" name="cameraPitch">
+          <property name="minimum">
+           <number>-90</number>
+          </property>
+          <property name="maximum">
+           <number>90</number>
+          </property>
+          <property name="pageStep">
+           <number>15</number>
+          </property>
+          <property name="value">
+           <number>35</number>
+          </property>
+          <property name="orientation">
+           <enum>Qt::Horizontal</enum>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QLabel" name="cameraDistanceLabel">
+          <property name="text">
+           <string>Distance</string>
+          </property>
+          <property name="buddy">
+           <cstring>cameraDistance</cstring>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QSlider" name="cameraDistance">
+          <property name="maximum">
+           <number>50</number>
+          </property>
+          <property name="value">
+           <number>30</number>
+          </property>
+          <property name="orientation">
+           <enum>Qt::Horizontal</enum>
+          </property>
+         </widget>
+        </item>
+       </layout>
+      </widget>
+     </item>
+     <item>
+      <widget class="QGroupBox" name="groupBox_2">
+       <property name="title">
+        <string>Light</string>
+       </property>
+       <layout class="QVBoxLayout" name="verticalLayout_3">
+        <item>
+         <widget class="QLabel" name="lightYawLabel">
+          <property name="text">
+           <string>Yaw</string>
+          </property>
+          <property name="buddy">
+           <cstring>lightYaw</cstring>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QSlider" name="lightYaw">
+          <property name="minimum">
+           <number>-180</number>
+          </property>
+          <property name="maximum">
+           <number>180</number>
+          </property>
+          <property name="pageStep">
+           <number>15</number>
+          </property>
+          <property name="orientation">
+           <enum>Qt::Horizontal</enum>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QLabel" name="lightPitchLabel">
+          <property name="text">
+           <string>Pitch</string>
+          </property>
+          <property name="buddy">
+           <cstring>lightPitch</cstring>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QSlider" name="lightPitch">
+          <property name="minimum">
+           <number>-90</number>
+          </property>
+          <property name="maximum">
+           <number>90</number>
+          </property>
+          <property name="pageStep">
+           <number>15</number>
+          </property>
+          <property name="value">
+           <number>60</number>
+          </property>
+          <property name="orientation">
+           <enum>Qt::Horizontal</enum>
+          </property>
+          <property name="invertedAppearance">
+           <bool>false</bool>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QLabel" name="lightDistanceLabel">
+          <property name="text">
+           <string>Distance</string>
+          </property>
+          <property name="buddy">
+           <cstring>lightDistance</cstring>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QSlider" name="lightDistance">
+          <property name="maximum">
+           <number>50</number>
+          </property>
+          <property name="value">
+           <number>10</number>
+          </property>
+          <property name="orientation">
+           <enum>Qt::Horizontal</enum>
+          </property>
+         </widget>
+        </item>
+       </layout>
+      </widget>
+     </item>
+     <item>
+      <widget class="QGroupBox" name="groupBox_3">
+       <property name="title">
+        <string>Lighting</string>
+       </property>
+       <layout class="QVBoxLayout" name="verticalLayout_4">
+        <item>
+         <widget class="QLabel" name="accumSigmaLabel">
+          <property name="text">
+           <string>Averaging radius</string>
+          </property>
+          <property name="buddy">
+           <cstring>accumSigma</cstring>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QSlider" name="accumSigma">
+          <property name="minimum">
+           <number>-100</number>
+          </property>
+          <property name="maximum">
+           <number>0</number>
+          </property>
+          <property name="value">
+           <number>-40</number>
+          </property>
+          <property name="orientation">
+           <enum>Qt::Horizontal</enum>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QLabel" name="accumScaleLabel">
+          <property name="text">
+           <string>Brightness</string>
+          </property>
+          <property name="buddy">
+           <cstring>accumScale</cstring>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QSlider" name="accumScale">
+          <property name="minimum">
+           <number>-100</number>
+          </property>
+          <property name="maximum">
+           <number>0</number>
+          </property>
+          <property name="value">
+           <number>-50</number>
+          </property>
+          <property name="orientation">
+           <enum>Qt::Horizontal</enum>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QLabel" name="label">
+          <property name="text">
+           <string>Reflections</string>
+          </property>
+          <property name="buddy">
+           <cstring>reflections</cstring>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QSpinBox" name="reflections">
+          <property name="maximum">
+           <number>20</number>
+          </property>
+          <property name="value">
+           <number>2</number>
+          </property>
+         </widget>
+        </item>
+       </layout>
+      </widget>
+     </item>
+     <item>
+      <widget class="QGroupBox" name="groupBox_4">
+       <property name="title">
+        <string>Show</string>
+       </property>
+       <layout class="QVBoxLayout" name="verticalLayout_5">
+        <item>
+         <widget class="QCheckBox" name="displayAxes">
+          <property name="text">
+           <string>Axes</string>
+          </property>
+          <property name="checked">
+           <bool>true</bool>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QCheckBox" name="displayShapes">
+          <property name="text">
+           <string>Shapes</string>
+          </property>
+          <property name="checked">
+           <bool>true</bool>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QCheckBox" name="displayEmitted">
+          <property name="text">
+           <string>Emitted rays</string>
+          </property>
+          <property name="checked">
+           <bool>false</bool>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QCheckBox" name="displayDirectHits">
+          <property name="text">
+           <string>Direct incident rays</string>
+          </property>
+          <property name="checked">
+           <bool>false</bool>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QCheckBox" name="displayIndirectHits">
+          <property name="text">
+           <string>Indirect incident rays</string>
+          </property>
+          <property name="checked">
+           <bool>false</bool>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QCheckBox" name="displayResult">
+          <property name="text">
+           <string>Average light</string>
+          </property>
+          <property name="checked">
+           <bool>true</bool>
+          </property>
+         </widget>
+        </item>
+       </layout>
+      </widget>
+     </item>
+     <item>
+      <spacer name="verticalSpacer">
+       <property name="orientation">
+        <enum>Qt::Vertical</enum>
+       </property>
+       <property name="sizeHint" stdset="0">
+        <size>
+         <width>20</width>
+         <height>385</height>
+        </size>
+       </property>
+      </spacer>
+     </item>
+    </layout>
+   </widget>
+  </widget>
+ </widget>
+ <customwidgets>
+  <customwidget>
+   <class>Viewport</class>
+   <extends>QWidget</extends>
+   <header>viewport.hxx</header>
+   <container>1</container>
+  </customwidget>
+ </customwidgets>
+ <resources/>
+ <connections>
+  <connection>
+   <sender>cameraYaw</sender>
+   <signal>valueChanged(int)</signal>
+   <receiver>MainWindow</receiver>
+   <slot>updateView()</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>1585</x>
+     <y>169</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>403</x>
+     <y>362</y>
+    </hint>
+   </hints>
+  </connection>
+  <connection>
+   <sender>cameraPitch</sender>
+   <signal>valueChanged(int)</signal>
+   <receiver>MainWindow</receiver>
+   <slot>updateView()</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>1585</x>
+     <y>225</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>403</x>
+     <y>362</y>
+    </hint>
+   </hints>
+  </connection>
+  <connection>
+   <sender>lightYaw</sender>
+   <signal>valueChanged(int)</signal>
+   <receiver>MainWindow</receiver>
+   <slot>updateView()</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>1585</x>
+     <y>385</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>403</x>
+     <y>362</y>
+    </hint>
+   </hints>
+  </connection>
+  <connection>
+   <sender>lightPitch</sender>
+   <signal>valueChanged(int)</signal>
+   <receiver>MainWindow</receiver>
+   <slot>updateView()</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>1585</x>
+     <y>441</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>403</x>
+     <y>362</y>
+    </hint>
+   </hints>
+  </connection>
+  <connection>
+   <sender>accumSigma</sender>
+   <signal>valueChanged(int)</signal>
+   <receiver>MainWindow</receiver>
+   <slot>updateView()</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>1585</x>
+     <y>601</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>399</x>
+     <y>299</y>
+    </hint>
+   </hints>
+  </connection>
+  <connection>
+   <sender>accumScale</sender>
+   <signal>valueChanged(int)</signal>
+   <receiver>MainWindow</receiver>
+   <slot>updateView()</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>1585</x>
+     <y>657</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>399</x>
+     <y>299</y>
+    </hint>
+   </hints>
+  </connection>
+  <connection>
+   <sender>cameraDistance</sender>
+   <signal>valueChanged(int)</signal>
+   <receiver>MainWindow</receiver>
+   <slot>updateView()</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>1489</x>
+     <y>271</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>799</x>
+     <y>599</y>
+    </hint>
+   </hints>
+  </connection>
+  <connection>
+   <sender>lightDistance</sender>
+   <signal>valueChanged(int)</signal>
+   <receiver>MainWindow</receiver>
+   <slot>updateView()</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>1489</x>
+     <y>487</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>799</x>
+     <y>599</y>
+    </hint>
+   </hints>
+  </connection>
+  <connection>
+   <sender>displayAxes</sender>
+   <signal>stateChanged(int)</signal>
+   <receiver>MainWindow</receiver>
+   <slot>updateView()</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>1489</x>
+     <y>799</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>799</x>
+     <y>599</y>
+    </hint>
+   </hints>
+  </connection>
+  <connection>
+   <sender>displayDirectHits</sender>
+   <signal>stateChanged(int)</signal>
+   <receiver>MainWindow</receiver>
+   <slot>updateView()</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>1489</x>
+     <y>901</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>799</x>
+     <y>599</y>
+    </hint>
+   </hints>
+  </connection>
+  <connection>
+   <sender>displayEmitted</sender>
+   <signal>stateChanged(int)</signal>
+   <receiver>MainWindow</receiver>
+   <slot>updateView()</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>1489</x>
+     <y>867</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>799</x>
+     <y>599</y>
+    </hint>
+   </hints>
+  </connection>
+  <connection>
+   <sender>displayIndirectHits</sender>
+   <signal>stateChanged(int)</signal>
+   <receiver>MainWindow</receiver>
+   <slot>updateView()</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>1489</x>
+     <y>935</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>799</x>
+     <y>599</y>
+    </hint>
+   </hints>
+  </connection>
+  <connection>
+   <sender>displayResult</sender>
+   <signal>stateChanged(int)</signal>
+   <receiver>MainWindow</receiver>
+   <slot>updateView()</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>1489</x>
+     <y>969</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>799</x>
+     <y>599</y>
+    </hint>
+   </hints>
+  </connection>
+  <connection>
+   <sender>displayShapes</sender>
+   <signal>stateChanged(int)</signal>
+   <receiver>MainWindow</receiver>
+   <slot>updateView()</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>1489</x>
+     <y>833</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>799</x>
+     <y>599</y>
+    </hint>
+   </hints>
+  </connection>
+  <connection>
+   <sender>reflections</sender>
+   <signal>valueChanged(int)</signal>
+   <receiver>MainWindow</receiver>
+   <slot>updateView()</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>1489</x>
+     <y>712</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>799</x>
+     <y>599</y>
+    </hint>
+   </hints>
+  </connection>
+ </connections>
+ <slots>
+  <slot>updateView()</slot>
+ </slots>
+</ui>

ui/src/viewport.cxx

@@ -0,0 +1,74 @@
+#include "viewport.hxx"
+
+#include <QApplication>
+#include <QEvent>
+#include <QGuiApplication>
+
+Viewport::Viewport(QWidget* parent, Qt::WindowFlags f)
+	: QWidget(parent, f) {
+	setAttribute(Qt::WA_DontCreateNativeAncestors);
+	setAttribute(Qt::WA_NativeWindow);
+	setAttribute(Qt::WA_PaintOnScreen);
+	setAttribute(Qt::WA_NoSystemBackground);
+}
+
+Viewport::~Viewport() = default;
+
+void Viewport::setView(RedrawArgs new_args) {
+	args = new_args;
+	update();
+}
+
+QPaintEngine* Viewport::paintEngine() const {
+	return nullptr;
+}
+
+bool Viewport::event(QEvent* event) {
+	switch (event->type()) {
+	case QEvent::Type::WinIdChange:
+		recreate();
+		break;
+	default:
+		break;
+	}
+	return QWidget::event(event);
+}
+
+void Viewport::paintEvent(QPaintEvent* event) {
+	if (!core)
+		recreate();
+	core->redraw(args);
+}
+
+void Viewport::resizeEvent(QResizeEvent* event) {
+	if (!core)
+		return;
+	updateSize();
+	QWidget::resizeEvent(event);
+}
+
+void Viewport::recreate() try {
+	auto* app = qobject_cast<QGuiApplication*>(QApplication::instance());
+	if (!app)
+		throw std::runtime_error("not a GUI application (WTF?)");
+
+	auto* native = app->nativeInterface<QNativeInterface::QX11Application>();
+	if (!native)
+		throw std::runtime_error("X11 interface is not available");
+
+	auto* xcb_connection = native->connection();
+	std::uint32_t x11_window = winId();
+
+	fprintf(stderr, "connection %p, window %#08x\n", xcb_connection, x11_window);
+
+	core.reset();
+	core = BoxCore::from_xcb(xcb_connection, x11_window);
+	updateSize();
+} catch (const std::exception& e) {
+	fprintf(stderr, "failed to recreate the viewport: %s", e.what());
+}
+
+void Viewport::updateSize() {
+	const QSize device_size = size() * devicePixelRatio();
+	core->configure(device_size.width(), device_size.height());
+}

ui/src/viewport.hxx

@@ -0,0 +1,28 @@
+#pragma once
+
+#include <QWidget>
+
+#include "api.hxx"
+
+class Viewport : public QWidget {
+	Q_OBJECT
+
+public:
+	explicit Viewport(QWidget* parent = nullptr, Qt::WindowFlags f = Qt::WindowFlags());
+	~Viewport() override;
+	QPaintEngine* paintEngine() const override;
+
+	void setView(RedrawArgs new_args);
+
+protected:
+	bool event(QEvent* event) override;
+	void paintEvent(QPaintEvent* event) override;
+	void resizeEvent(QResizeEvent* event) override;
+
+private:
+	BoxCore core;
+	RedrawArgs args = {};
+
+	void recreate();
+	void updateSize();
+};