Send many rays per pixel manually

src/bin/minitracer/main.rs

@@ -32,6 +32,7 @@ fn make_viewport(w: u32, h: u32) -> [Vertex; 4] {
 }
 
 const N_SPHERES: u32 = 100;
+const RAYS_PER_PIXEL: u32 = 4;
 
 fn main() {
 	let event_loop = EventLoop::new().unwrap();
@@ -89,7 +90,6 @@ fn main() {
 						return;
 					}
 					time += 1. / 60.;
-					frame += 1;
 					let spheres: Vec<_> = sphere_params.iter().map(|p| p.to_sphere(time)).collect();
 					let data = TracerData::new(&device, &tracer, &spheres);
 
@@ -98,11 +98,7 @@ fn main() {
 					let size = output.texture.size();
 					let hdr = device.create_texture(&wgpu::TextureDescriptor {
 						label: None,
-						size: wgpu::Extent3d {
+						size,
-							width: 2 * size.width,
-							height: 2 * size.height,
-							depth_or_array_layers: 1,
-						},
 						mip_level_count: 1,
 						sample_count: 1,
 						dimension: wgpu::TextureDimension::D2,
@@ -127,6 +123,8 @@ fn main() {
 							occlusion_query_set: None,
 							timestamp_writes: None,
 						});
+						for _ in 0..RAYS_PER_PIXEL {
+							frame += 1;
 							tracer.render(
 								&mut render_pass,
 								&data,
@@ -139,6 +137,7 @@ fn main() {
 								},
 							);
 						}
+					}
 					{
 						let mut render_pass = encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
 							label: None,
@@ -154,7 +153,14 @@ fn main() {
 							occlusion_query_set: None,
 							timestamp_writes: None,
 						});
-						presenter.render(&device, &mut render_pass, &hdr);
+						presenter.render(
+							&device,
+							&mut render_pass,
+							&hdr,
+							present::Params {
+								divisor: RAYS_PER_PIXEL as f32,
+							},
+						);
 					}
 					queue.submit(std::iter::once(encoder.finish()));
 					output.present();

src/bin/minitracer/present.rs

@@ -10,6 +10,12 @@ struct Vertex {
 	pub screen: Vec2,
 }
 
+#[derive(Debug, Clone, Copy, Pod, Zeroable)]
+#[repr(C)]
+pub struct Params {
+	pub divisor: f32,
+}
+
 pub struct Presenter {
 	view_buf: wgpu::Buffer,
 	sampler: wgpu::Sampler,
@@ -80,7 +86,18 @@ impl Presenter {
 		}
 	}
 
-	pub fn render(&self, device: &wgpu::Device, pass: &mut wgpu::RenderPass, texture: &wgpu::TextureView) {
+	pub fn render(
+		&self,
+		device: &wgpu::Device,
+		pass: &mut wgpu::RenderPass,
+		texture: &wgpu::TextureView,
+		params: Params,
+	) {
+		let params_buf = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
+			label: None,
+			contents: bytes_of(&params),
+			usage: wgpu::BufferUsages::UNIFORM,
+		});
 		let bindings = device.create_bind_group(&wgpu::BindGroupDescriptor {
 			label: None,
 			layout: &self.pipeline.get_bind_group_layout(0),
@@ -93,6 +110,10 @@ impl Presenter {
 					binding: 1,
 					resource: wgpu::BindingResource::TextureView(texture),
 				},
+				wgpu::BindGroupEntry {
+					binding: 2,
+					resource: params_buf.as_entire_binding(),
+				},
 			],
 		});
 		pass.set_pipeline(&self.pipeline);

src/bin/minitracer/present.wgsl

@@ -1,3 +1,7 @@
+struct Params {
+	divisor: f32,
+}
+
 struct Vertex {
 	@location(0) screen: vec2f,
 }
@@ -9,6 +13,7 @@ struct Varying {
 
 @group(0) @binding(0) var smp: sampler;
 @group(0) @binding(1) var tex: texture_2d<f32>;
+@group(0) @binding(2) var<uniform> params: Params;
 
 @vertex
 fn on_vertex(in: Vertex) -> Varying {
@@ -19,7 +24,7 @@ fn on_vertex(in: Vertex) -> Varying {
 
 @fragment
 fn on_fragment(in: Varying) -> @location(0) vec4f {
-	let pixel = textureSample(tex, smp, in.tex);
+	let pixel = textureSample(tex, smp, in.tex) / params.divisor;
 	return vec4(rational_tone_map(pixel.xyz), 1.0);
 }
 

src/bin/minitracer/trace.wgsl

@@ -69,7 +69,9 @@ fn trace_fragment(in: Varying) -> vec4f {
 	var result = vec4(0.0, 0.0, 0.0, 0.0);
 	var color = vec3(1.0, 1.0, 1.0);
 	pos = in.eye;
-	ray = normalize(in.world - in.eye);
+	let off_px = vec2(rand_float(), rand_float()) - .5;
+	let off_w = mat2x3(dpdx(in.world), dpdy(in.world));
+	ray = normalize(in.world + off_w * off_px - in.eye);
 
 	for (var k = 0; k < params.max_reflections; k++) {
 		var sphere = -1;