From a60a25e9ba5400bd308d302bd08b30a826a1e395 Mon Sep 17 00:00:00 2001
From: tolelom <98kimsungmin@naver.com>
Date: Thu, 26 Mar 2026 15:25:26 +0900
Subject: [PATCH] docs: add SSGI quality (bilateral blur + temporal
 accumulation) design spec

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
---
 .../specs/2026-03-26-ssgi-quality-design.md   | 107 ++++++++++++++++++
 1 file changed, 107 insertions(+)
 create mode 100644 docs/superpowers/specs/2026-03-26-ssgi-quality-design.md

diff --git a/docs/superpowers/specs/2026-03-26-ssgi-quality-design.md b/docs/superpowers/specs/2026-03-26-ssgi-quality-design.md
new file mode 100644
index 0000000..8c0d413
--- /dev/null
+++ b/docs/superpowers/specs/2026-03-26-ssgi-quality-design.md
@@ -0,0 +1,107 @@
+# SSGI Quality Improvement Design (Bilateral Blur + Temporal Accumulation)
+
+## Overview
+
+SSGI 출력의 노이즈를 줄이기 위해 bilateral blur와 temporal accumulation 필터를 추가한다.
+
+## Scope
+
+- Bilateral blur 셰이더: depth/normal 기반 edge-aware blur
+- Temporal accumulation: 이전 프레임 SSGI와 현재 프레임을 블렌딩
+- 각각 독립적 풀스크린 패스
+
+## Bilateral Blur
+
+Depth와 normal 차이를 가중치로 사용하여 edge를 보존하면서 노이즈를 줄이는 블러.
+
+### 셰이더 (bilateral_blur.wgsl)
+
+```wgsl
+@group(0) @binding(0) var input_tex: texture_2d<f32>;     // SSGI 출력
+@group(0) @binding(1) var depth_tex: texture_2d<f32>;     // G-Buffer depth
+@group(0) @binding(2) var normal_tex: texture_2d<f32>;    // G-Buffer normal
+@group(0) @binding(3) var output_tex: texture_storage_2d<rgba16float, write>;
+
+// 5x5 bilateral kernel
+// weight = gaussian(spatial_dist) * exp(-|depth_diff|/sigma_d) * max(dot(n1,n2),0)^sigma_n
+```
+
+컴퓨트 셰이더로 구현. 워크그룹 16x16.
+
+### BilateralBlur 구조체
+
+```rust
+pub struct BilateralBlur {
+    pipeline: wgpu::ComputePipeline,
+    bind_group_layout: wgpu::BindGroupLayout,
+}
+```
+
+- `new(device)` — 파이프라인 생성
+- `dispatch(encoder, ssgi_view, depth_view, normal_view, output_view, width, height)` — 실행
+
+### 파라미터
+- kernel_size: 5 (하드코딩)
+- sigma_spatial: 2.0
+- sigma_depth: 0.1
+- sigma_normal: 16.0
+
+## Temporal Accumulation
+
+이전 프레임의 결과와 현재 프레임을 블렌딩하여 시간에 따라 노이즈를 줄임.
+
+### 셰이더 (temporal_accum.wgsl)
+
+```wgsl
+@group(0) @binding(0) var current_tex: texture_2d<f32>;   // 현재 프레임 (blurred SSGI)
+@group(0) @binding(1) var history_tex: texture_2d<f32>;   // 이전 프레임 결과
+@group(0) @binding(2) var output_tex: texture_storage_2d<rgba16float, write>;
+
+// blend_factor = 0.1 (10% 새 프레임, 90% 히스토리)
+// output = mix(history, current, blend_factor)
+```
+
+### TemporalAccumulation 구조체
+
+```rust
+pub struct TemporalAccumulation {
+    pipeline: wgpu::ComputePipeline,
+    bind_group_layout: wgpu::BindGroupLayout,
+    history_texture: wgpu::Texture,  // 이전 프레임 저장
+    history_view: wgpu::TextureView,
+    pub blend_factor: f32,           // 0.1
+}
+```
+
+- `new(device, width, height)` — 히스토리 텍스처 + 파이프라인
+- `dispatch(encoder, current_view, output_view, width, height)` — 블렌딩 실행
+- `swap_history(new_view)` — 출력을 히스토리로 복사 (또는 ping-pong)
+
+### Ping-Pong 패턴
+텍스처 2개를 교대로 사용:
+- Frame N: read history_A, write history_B → output = history_B
+- Frame N+1: read history_B, write history_A → output = history_A
+
+## 적용 순서
+
+```
+SSGI Pass → [Bilateral Blur] → [Temporal Accumulation] → Lighting Pass (기존 SSGI 텍스처 대체)
+```
+
+## File Structure
+
+- `crates/voltex_renderer/src/bilateral_blur.rs` — BilateralBlur
+- `crates/voltex_renderer/src/bilateral_blur.wgsl` — 컴퓨트 셰이더
+- `crates/voltex_renderer/src/temporal_accum.rs` — TemporalAccumulation
+- `crates/voltex_renderer/src/temporal_accum.wgsl` — 컴퓨트 셰이더
+- `crates/voltex_renderer/src/lib.rs` — 모듈 추가
+
+## Testing
+
+### Bilateral Blur (순수 수학)
+- gaussian weight 계산 검증
+- bilateral weight: depth 차이 클수록 weight 작아지는지
+
+### Temporal Accumulation (순수 수학)
+- blend: factor=0.0 → history 그대로, factor=1.0 → current 그대로
+- factor=0.1 → 90% history + 10% current