From 2c5e0dd313d56fb7885b2f9996f96c8d356bac27 Mon Sep 17 00:00:00 2001
From: Kelsi <kelsihates2fa@gmail.com>
Date: Sun, 22 Feb 2026 09:47:39 -0800
Subject: [PATCH] Fix Vulkan shadow light direction and restore ground-clutter
 cutout visibility

---
 assets/shaders/m2.frag.glsl   | 5 ++++-
 src/rendering/m2_renderer.cpp | 6 ++++--
 src/rendering/renderer.cpp    | 6 ++++--
 3 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/assets/shaders/m2.frag.glsl b/assets/shaders/m2.frag.glsl
index c1a08392..bdc8e0e9 100644
--- a/assets/shaders/m2.frag.glsl
+++ b/assets/shaders/m2.frag.glsl
@@ -42,6 +42,9 @@ void main() {
     if (alphaTest == 2) {
         // Vegetation cutout: lower threshold to preserve leaf coverage at grazing angles.
         alphaCutoff = 0.33;
+    } else if (alphaTest == 3) {
+        // Ground detail clutter (grass/small cards) needs softer clipping.
+        alphaCutoff = 0.20;
     } else if (alphaTest != 0) {
         alphaCutoff = 0.35;
     }
@@ -112,7 +115,7 @@ void main() {
     }
     // Foliage cutout should stay opaque after alpha discard to avoid
     // view-angle translucency artifacts.
-    if (alphaTest == 2) {
+    if (alphaTest == 2 || alphaTest == 3) {
         outAlpha = 1.0 * fadeAlpha;
     }
     outColor = vec4(result, outAlpha);
diff --git a/src/rendering/m2_renderer.cpp b/src/rendering/m2_renderer.cpp
index 2d8a34f6..dd4f3ac0 100644
--- a/src/rendering/m2_renderer.cpp
+++ b/src/rendering/m2_renderer.cpp
@@ -2073,7 +2073,7 @@ void M2Renderer::render(VkCommandBuffer cmd, VkDescriptorSet perFrameSet, const
         }
         if (model.isGroundDetail) {
             // Keep clutter local so distant grass doesn't overdraw the scene.
-            effectiveMaxDistSq *= 0.45f;
+            effectiveMaxDistSq *= 0.75f;
         }
         // Removed aggressive small-object distance caps to prevent city pop-out
         // Small props (barrels, lanterns, etc.) now use same distance as larger objects
@@ -2360,7 +2360,9 @@ void M2Renderer::render(VkCommandBuffer cmd, VkDescriptorSet perFrameSet, const
                     }
                     // Cutout path for foliage/cards.
                     if (forceCutout) {
-                        mat->alphaTest = foliageCutout ? 2 : 1;
+                        // Ground clutter uses a softer dedicated cutout mode so thin
+                        // grass cards are not over-discarded.
+                        mat->alphaTest = model.isGroundDetail ? 3 : (foliageCutout ? 2 : 1);
                         if (model.isGroundDetail) {
                             mat->unlit = 0;
                         }
diff --git a/src/rendering/renderer.cpp b/src/rendering/renderer.cpp
index e5b143aa..1e714d21 100644
--- a/src/rendering/renderer.cpp
+++ b/src/rendering/renderer.cpp
@@ -3596,12 +3596,14 @@ glm::mat4 Renderer::computeLightSpaceMatrix() {
     constexpr float kShadowNearPlane = 1.0f;
     constexpr float kShadowFarPlane = 600.0f;
 
-    // Use active lighting direction so shadow projection matches sun/celestial.
+    // Use active lighting direction so shadow projection matches main shading.
+    // Fragment shaders derive lighting with `ldir = normalize(-lightDir.xyz)`,
+    // therefore shadow rays must use -directionalDir to stay aligned.
     glm::vec3 sunDir = glm::normalize(glm::vec3(-0.3f, -0.7f, -0.6f));
     if (lightingManager) {
         const auto& lighting = lightingManager->getLightingParams();
         if (glm::length(lighting.directionalDir) > 0.001f) {
-            sunDir = glm::normalize(lighting.directionalDir);
+            sunDir = glm::normalize(-lighting.directionalDir);
         }
     }
     // Shadow camera expects light rays pointing downward in render space (Z up).