From fd4fe52744e51ae3b25d4de4e501c861f5d7650e Mon Sep 17 00:00:00 2001
From: hydrogendeuteride <dumpsterowner@gmail.com>
Date: Wed, 22 Oct 2025 22:26:50 +0900
Subject: [PATCH] ADD: stabilized CSM 2

---
 src/scene/vk_scene.cpp | 34 ++++++++--------------------------
 1 file changed, 8 insertions(+), 26 deletions(-)

diff --git a/src/scene/vk_scene.cpp b/src/scene/vk_scene.cpp
index b680ebc..7933910 100644
--- a/src/scene/vk_scene.cpp
+++ b/src/scene/vk_scene.cpp
@@ -113,24 +113,19 @@ void SceneManager::update_scene()
         const glm::mat4 invView = glm::inverse(view);
         const glm::vec3 camPos = glm::vec3(invView[3]);
 
-        // Sun direction and light basis (robust)
         glm::vec3 L = glm::normalize(-glm::vec3(sceneData.sunlightDirection));
         if (glm::length(L) < 1e-5f) L = glm::vec3(0.0f, -1.0f, 0.0f);
         const glm::vec3 worldUp(0.0f, 1.0f, 0.0f);
         glm::vec3 right = glm::cross(L, worldUp);
         if (glm::length2(right) < 1e-6f) right = glm::vec3(1, 0, 0);
         right = glm::normalize(right);
-        glm::vec3 up = glm::normalize(glm::cross(right, L));
-
-        // 0) Legacy near/simple shadow (cascade 0 그대로)
-        {
+        glm::vec3 up = glm::normalize(glm::cross(right, L)); {
             const float orthoRange = 10.0f;
             const float nearDist = 0.1f;
             const float farDist = 200.0f;
-            const glm::vec3 lightPos = camPos - L * 180.0f;
+            const glm::vec3 lightPos = camPos - L * 50.0f;
             const glm::mat4 viewLight = glm::lookAtRH(lightPos, camPos, up);
 
-            // ⚠️ API에 맞게 ZO/NO를 고르세요 (Vulkan/D3D: ZO, OpenGL 기본: NO)
             const glm::mat4 projLight = glm::orthoRH_ZO(-orthoRange, orthoRange, -orthoRange, orthoRange,
                                                         nearDist, farDist);
 
@@ -139,10 +134,9 @@ void SceneManager::update_scene()
             sceneData.lightViewProjCascades[0] = lightVP;
         }
 
-        // 1) Cascade split distances (뷰공간 +Z를 "전방 거리"로 사용)
         const float farView = kShadowCSMFar;
-        const float nearSplit = 5.0f; // 0번(레거시)와 CSM 경계
-        const float lambda = 0.7f; // practical split
+        const float nearSplit = 5.0f;
+        const float lambda = 1.0f;
         float splits[3]{};
         for (int i = 1; i <= 3; ++i)
         {
@@ -153,9 +147,7 @@ void SceneManager::update_scene()
         }
         sceneData.cascadeSplitsView = glm::vec4(nearSplit, splits[0], splits[1], farView);
 
-        // 2) 뷰공간 슬라이스 [zn, zf]의 월드 코너 계산
         auto frustum_corners_world = [&](float zn, float zf) {
-            // 카메라는 뷰공간 -Z를 바라봄. 우리는 "전방거리"를 양수로 넣고 z는 -zn, -zf.
             const float tanHalfFov = tanf(fov * 0.5f);
             const float yN = tanHalfFov * zn;
             const float xN = yN * aspect;
@@ -175,14 +167,12 @@ void SceneManager::update_scene()
         auto build_light_matrix_for_slice = [&](float zNearVS, float zFarVS) {
             auto ws = frustum_corners_world(zNearVS, zFarVS);
 
-            // 라이트 뷰: 슬라이스 센터를 본다
             glm::vec3 center(0.0f);
             for (auto &p: ws) center += p;
             center *= (1.0f / 8.0f);
-            const float lightPullback = 50.0f; // 충분히 뒤로 빼서 안정화
+            const float lightPullback = 20.0f;
             glm::mat4 V = glm::lookAtRH(center - L * lightPullback, center, up);
 
-            // 라이트 공간으로 투영 후 AABB
             glm::vec3 minLS(FLT_MAX), maxLS(-FLT_MAX);
             for (auto &p: ws)
             {
@@ -191,35 +181,28 @@ void SceneManager::update_scene()
                 maxLS = glm::max(maxLS, q);
             }
 
-            // XY 반경/센터, 살짝 여유
             glm::vec2 extXY = glm::vec2(maxLS.x - minLS.x, maxLS.y - minLS.y);
             float radius = 0.5f * glm::max(extXY.x, extXY.y);
             radius = radius * kShadowCascadeRadiusScale + kShadowCascadeRadiusMargin;
 
             glm::vec2 centerXY = 0.5f * glm::vec2(maxLS.x + minLS.x, maxLS.y + minLS.y);
 
-            // Texel snapping (안정화)
             const float texel = (2.0f * radius) / float(kShadowMapResolution);
             centerXY.x = floorf(centerXY.x / texel) * texel;
             centerXY.y = floorf(centerXY.y / texel) * texel;
 
-            // 스냅된 XY 센터를 반영하도록 라이트 뷰를 라이트공간에서 평행이동
             glm::mat4 Vsnapped = glm::translate(glm::mat4(1.0f),
                                                 -glm::vec3(centerXY.x, centerXY.y, 0.0f)) * V;
 
-            // 깊이 범위(표준 Z, reversed-Z 안 씀)
-            // lookAtRH는 -Z 쪽을 앞(카메라 전방)으로 둔다: 가까운 점 z는 덜 음수(값이 큰 쪽), 먼 점은 더 음수(값이 작은 쪽)
-            const float zPad = 50.0f; // 슬라이스 앞뒤 여유
-            float zNear = glm::max(0.1f, -maxLS.z - zPad); // "가까움": -z(덜음수) → 양수 거리
-            float zFar = -minLS.z + zPad; // "멀리":   -z(더음수) → 더 큰 양수
+            const float zPad = 50.0f;
+            float zNear = glm::max(0.1f, -maxLS.z - zPad);
+            float zFar = -minLS.z + zPad;
 
-            // ⚠️ API에 맞게 ZO/NO를 선택
             glm::mat4 P = glm::orthoRH_ZO(-radius, radius, -radius, radius, zNear, zFar);
 
             return P * Vsnapped;
         };
 
-        // 3) Cascades 1..3 채우기
         float prev = nearSplit;
         for (int ci = 1; ci < kShadowCascadeCount; ++ci)
         {
@@ -229,7 +212,6 @@ void SceneManager::update_scene()
         }
     }
 
-
     auto end = std::chrono::system_clock::now();
     auto elapsed = std::chrono::duration_cast<std::chrono::microseconds>(end - start);
     stats.scene_update_time = elapsed.count() / 1000.f;