From 3cbb12d1b4691fbdb49bc7c68695be71009f2de8 Mon Sep 17 00:00:00 2001
From: Johann Muszynski <johann.muszynski@gmail.com>
Date: Mon, 24 Jun 2024 17:36:48 +0300
Subject: [PATCH] temporal accumulation with EMA

---
 src/pt/deferred_renderer.cpp               |  4 +++-
 src/pt/deferred_renderer.hpp               |  7 ++++---
 src/pt/deferred_renderer_resolve_pass.wgsl | 13 ++++++++++++-
 src/pt/shader_source.hpp                   | 13 ++++++++++++-
 4 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/src/pt/deferred_renderer.cpp b/src/pt/deferred_renderer.cpp
index b1457a1..1f94670 100644
--- a/src/pt/deferred_renderer.cpp
+++ b/src/pt/deferred_renderer.cpp
@@ -361,6 +361,7 @@ void DeferredRenderer::render(
             renderDesc.targetTextureView,
             framebufferSize,
             renderDesc.exposure,
+            frameCount,
             gui);
     }
     wgpuCommandEncoderWriteTimestamp(
@@ -1970,10 +1971,11 @@ void DeferredRenderer::ResolvePass::render(
     WGPUTextureView          targetTextureView,
     const Extent2f&          fbsize,
     const float              exposure,
+    const std::uint32_t      frameCount,
     Gui&                     gui)
 {
     {
-        const Uniforms uniforms{glm::vec2(fbsize.x, fbsize.y), exposure, 0.f};
+        const Uniforms uniforms{glm::vec2(fbsize.x, fbsize.y), exposure, frameCount};
         wgpuQueueWriteBuffer(
             gpuContext.queue, mUniformBuffer.ptr(), 0, &uniforms, sizeof(Uniforms));
     }
diff --git a/src/pt/deferred_renderer.hpp b/src/pt/deferred_renderer.hpp
index ec10102..b656605 100644
--- a/src/pt/deferred_renderer.hpp
+++ b/src/pt/deferred_renderer.hpp
@@ -245,9 +245,9 @@ class DeferredRenderer
 
         struct Uniforms
         {
-            glm::vec2 framebufferSize;
-            float     exposure;
-            float     _padding;
+            glm::vec2     framebufferSize;
+            float         exposure;
+            std::uint32_t frameCount;
         };
 
     public:
@@ -270,6 +270,7 @@ class DeferredRenderer
             WGPUTextureView    targetTextureView,
             const Extent2f&    framebufferSize,
             float              exposure,
+            std::uint32_t      frameCount,
             Gui&               gui);
     };
 
diff --git a/src/pt/deferred_renderer_resolve_pass.wgsl b/src/pt/deferred_renderer_resolve_pass.wgsl
index 527e27f..18e6c24 100644
--- a/src/pt/deferred_renderer_resolve_pass.wgsl
+++ b/src/pt/deferred_renderer_resolve_pass.wgsl
@@ -20,6 +20,7 @@ fn vsMain(in: VertexInput) -> VertexOutput {
 struct Uniforms {
     framebufferSize: vec2f,
     exposure: f32,
+    frameCount: u32,
 }
 
 // TODO: consider merging these into one bind group
@@ -35,7 +36,17 @@ fn fsMain(in: VertexOutput) -> @location(0) vec4f {
     let textureIdx = vec2u(floor(uv * uniforms.framebufferSize));
     let sampleBufferIdx = textureIdx.y * u32(uniforms.framebufferSize.x) + textureIdx.x;
     let sample: array<f32, 3> = sampleBuffer[sampleBufferIdx];
-    let color = vec3f(sample[0], sample[1], sample[2]);
+    let currentColor = vec3f(sample[0], sample[1], sample[2]);
+    var color = vec3f(0f);
+    if uniforms.frameCount == 0u {
+        accumulationBuffer[sampleBufferIdx] = sample;
+        color = currentColor;
+    } else {
+        let previousSample: array<f32, 3> = accumulationBuffer[sampleBufferIdx];
+        let previousColor = vec3f(previousSample[0], previousSample[1], previousSample[2]);
+        color = 0.1 * currentColor + 0.9 * previousColor;
+        accumulationBuffer[sampleBufferIdx] = array<f32, 3>(color.r, color.g, color.b);
+    }
 
     let rgb = acesFilmic(uniforms.exposure * color);
     let srgb = pow(rgb, vec3(1f / 2.2f));
diff --git a/src/pt/shader_source.hpp b/src/pt/shader_source.hpp
index 88680b3..144dc3f 100644
--- a/src/pt/shader_source.hpp
+++ b/src/pt/shader_source.hpp
@@ -1295,6 +1295,7 @@ fn vsMain(in: VertexInput) -> VertexOutput {
 struct Uniforms {
     framebufferSize: vec2f,
     exposure: f32,
+    frameCount: u32,
 }
 
 // TODO: consider merging these into one bind group
@@ -1310,7 +1311,17 @@ fn fsMain(in: VertexOutput) -> @location(0) vec4f {
     let textureIdx = vec2u(floor(uv * uniforms.framebufferSize));
     let sampleBufferIdx = textureIdx.y * u32(uniforms.framebufferSize.x) + textureIdx.x;
     let sample: array<f32, 3> = sampleBuffer[sampleBufferIdx];
-    let color = vec3f(sample[0], sample[1], sample[2]);
+    let currentColor = vec3f(sample[0], sample[1], sample[2]);
+    var color = vec3f(0f);
+    if uniforms.frameCount == 0u {
+        accumulationBuffer[sampleBufferIdx] = sample;
+        color = currentColor;
+    } else {
+        let previousSample: array<f32, 3> = accumulationBuffer[sampleBufferIdx];
+        let previousColor = vec3f(previousSample[0], previousSample[1], previousSample[2]);
+        color = 0.1 * currentColor + 0.9 * previousColor;
+        accumulationBuffer[sampleBufferIdx] = array<f32, 3>(color.r, color.g, color.b);
+    }
 
     let rgb = acesFilmic(uniforms.exposure * color);
     let srgb = pow(rgb, vec3(1f / 2.2f));