Two-pass render for a much smoother look

src/bin/minitracer/main.rs

@@ -2,6 +2,7 @@ use std::error::Error;
 
 use glam::{vec2, vec3};
 use image::ImageReader;
+use present::Presenter;
 use trace::{Tracer, TracerData, TracerEnv, Vertex};
 use winit::{
 	event::{Event, WindowEvent},
@@ -10,6 +11,7 @@ use winit::{
 };
 
 mod anim;
+mod present;
 mod trace;
 
 pub use trace::Sphere;
@@ -65,6 +67,8 @@ fn main() {
 	};
 	let tracer_env = TracerEnv::new(&device, &tracer, &envmap);
 
+	let presenter = Presenter::new(&device, format);
+
 	let mut time = 0.0;
 
 	let mut surface_configured = false;
@@ -101,7 +105,41 @@ fn main() {
 
 					let output = surface.get_current_texture().unwrap();
 					let view = output.texture.create_view(&wgpu::TextureViewDescriptor::default());
+					let size = output.texture.size();
+					let buf = device.create_texture(&wgpu::TextureDescriptor {
+						label: None,
+						size: wgpu::Extent3d {
+							width: 2 * size.width,
+							height: 2 * size.height,
+							depth_or_array_layers: 1,
+						},
+						mip_level_count: 1,
+						sample_count: 1,
+						dimension: wgpu::TextureDimension::D2,
+						format,
+						usage: wgpu::TextureUsages::RENDER_ATTACHMENT | wgpu::TextureUsages::TEXTURE_BINDING,
+						view_formats: &[],
+					});
+					let buf = buf.create_view(&wgpu::TextureViewDescriptor::default());
 					let mut encoder = device.create_command_encoder(&wgpu::CommandEncoderDescriptor { label: None });
+					{
+						let mut render_pass = encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
+							label: None,
+							color_attachments: &[Some(wgpu::RenderPassColorAttachment {
+								view: &buf,
+								resolve_target: None,
+								ops: wgpu::Operations {
+									load: wgpu::LoadOp::Clear(wgpu::Color::TRANSPARENT),
+									store: wgpu::StoreOp::Store,
+								},
+							})],
+							depth_stencil_attachment: None,
+							occlusion_query_set: None,
+							timestamp_writes: None,
+						});
+						tracer.render(&mut render_pass, &data, &tracer_env);
+					}
+					{
 						let mut render_pass = encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
 							label: None,
 							color_attachments: &[Some(wgpu::RenderPassColorAttachment {
@@ -116,8 +154,8 @@ fn main() {
 							occlusion_query_set: None,
 							timestamp_writes: None,
 						});
-					tracer.render(&mut render_pass, &data, &tracer_env);
-					drop(render_pass);
+						presenter.render(&device, &mut render_pass, &buf);
+					}
 					queue.submit(std::iter::once(encoder.finish()));
 					output.present();
 				}

src/bin/minitracer/present.rs

@@ -0,0 +1,103 @@
+use std::mem::offset_of;
+
+use bytemuck::{bytes_of, Pod, Zeroable};
+use glam::{vec2, Vec2};
+use wgpu::util::DeviceExt;
+
+#[derive(Debug, Clone, Copy, Pod, Zeroable)]
+#[repr(C)]
+struct Vertex {
+	pub screen: Vec2,
+}
+
+pub struct Presenter {
+	view_buf: wgpu::Buffer,
+	sampler: wgpu::Sampler,
+	pipeline: wgpu::RenderPipeline,
+}
+
+static SHADER: &str = include_str!("present.wgsl");
+
+impl Presenter {
+	pub fn new(device: &wgpu::Device, format: wgpu::TextureFormat) -> Self {
+		let view_buf = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
+			label: None,
+			contents: bytes_of(&[(0., 0.), (1., 0.), (0., 1.), (1., 1.)].map(|(x, y)| Vertex { screen: vec2(x, y) })),
+			usage: wgpu::BufferUsages::VERTEX,
+		});
+		let shader = device.create_shader_module(wgpu::ShaderModuleDescriptor {
+			label: None,
+			source: wgpu::ShaderSource::Wgsl(SHADER.into()),
+		});
+		let pipeline = device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
+			label: None,
+			layout: None,
+			vertex: wgpu::VertexState {
+				module: &shader,
+				entry_point: None,
+				compilation_options: wgpu::PipelineCompilationOptions::default(),
+				buffers: &[wgpu::VertexBufferLayout {
+					array_stride: size_of::<Vertex>() as u64,
+					step_mode: wgpu::VertexStepMode::Vertex,
+					attributes: &[wgpu::VertexAttribute {
+						shader_location: 0,
+						offset: offset_of!(Vertex, screen) as u64,
+						format: wgpu::VertexFormat::Float32x2,
+					}],
+				}],
+			},
+			primitive: wgpu::PrimitiveState {
+				topology: wgpu::PrimitiveTopology::TriangleStrip,
+				..Default::default()
+			},
+			depth_stencil: None,
+			multisample: wgpu::MultisampleState {
+				count: 1,
+				mask: !0,
+				alpha_to_coverage_enabled: false,
+			},
+			fragment: Some(wgpu::FragmentState {
+				module: &shader,
+				entry_point: None,
+				compilation_options: wgpu::PipelineCompilationOptions::default(),
+				targets: &[Some(wgpu::ColorTargetState {
+					format,
+					blend: Some(wgpu::BlendState::REPLACE),
+					write_mask: wgpu::ColorWrites::ALL,
+				})],
+			}),
+			multiview: None,
+			cache: None,
+		});
+		let sampler = device.create_sampler(&wgpu::SamplerDescriptor {
+			min_filter: wgpu::FilterMode::Linear,
+			..Default::default()
+		});
+		Self {
+			view_buf,
+			sampler,
+			pipeline,
+		}
+	}
+
+	pub fn render(&self, device: &wgpu::Device, pass: &mut wgpu::RenderPass, texture: &wgpu::TextureView) {
+		let bindings = device.create_bind_group(&wgpu::BindGroupDescriptor {
+			label: None,
+			layout: &self.pipeline.get_bind_group_layout(0),
+			entries: &[
+				wgpu::BindGroupEntry {
+					binding: 0,
+					resource: wgpu::BindingResource::Sampler(&self.sampler),
+				},
+				wgpu::BindGroupEntry {
+					binding: 1,
+					resource: wgpu::BindingResource::TextureView(texture),
+				},
+			],
+		});
+		pass.set_pipeline(&self.pipeline);
+		pass.set_vertex_buffer(0, self.view_buf.slice(..));
+		pass.set_bind_group(0, &bindings, &[]);
+		pass.draw(0..4, 0..1);
+	}
+}

src/bin/minitracer/present.wgsl

@@ -0,0 +1,21 @@
+struct Vertex {
+	@location(0) screen: vec2f,
+}
+
+struct Varying {
+	@location(0) tex: vec2f,
+	@builtin(position) v: vec4f,
+}
+
+@group(0) @binding(0) var smp: sampler;
+@group(0) @binding(1) var tex: texture_2d<f32>;
+
+@vertex
+fn on_vertex(in: Vertex) -> Varying {
+	return Varying(in.screen, vec4(2.0 * in.screen - 1.0, 0.0, 1.0));
+}
+
+@fragment
+fn on_fragment(in: Varying) -> @location(0) vec4f {
+	return textureSample(tex, smp, in.tex);
+}