Add distance culling to shadow passes for CPU-bound shadow perf

All three shadow renderers (WMO, M2, Character) were iterating every
loaded instance with zero culling. Now skip instances outside the
180-unit shadow frustum radius via squared-distance check.

src/rendering/character_renderer.cpp

@@ -2302,7 +2302,8 @@ bool CharacterRenderer::initializeShadow(VkRenderPass shadowRenderPass) {
     return true;
 }
 
-void CharacterRenderer::renderShadow(VkCommandBuffer cmd, const glm::mat4& lightSpaceMatrix) {
+void CharacterRenderer::renderShadow(VkCommandBuffer cmd, const glm::mat4& lightSpaceMatrix,
+                                     const glm::vec3& shadowCenter, float shadowRadius) {
     if (!shadowPipeline_ || !shadowParamsSet_) return;
     if (instances.empty() || models.empty()) return;
 
@@ -2316,10 +2317,15 @@ void CharacterRenderer::renderShadow(VkCommandBuffer cmd, const glm::mat4& light
 
     struct ShadowPush { glm::mat4 lightSpaceMatrix; glm::mat4 model; };
 
+    const float shadowRadiusSq = shadowRadius * shadowRadius;
     for (auto& pair : instances) {
         auto& inst = pair.second;
         if (!inst.visible) continue;
 
+        // Distance cull against shadow frustum
+        glm::vec3 diff = inst.position - shadowCenter;
+        if (glm::dot(diff, diff) > shadowRadiusSq) continue;
+
         auto modelIt = models.find(inst.modelId);
         if (modelIt == models.end()) continue;
         const M2ModelGPU& gpuModel = modelIt->second;

src/rendering/m2_renderer.cpp

@@ -2607,11 +2607,13 @@ bool M2Renderer::initializeShadow(VkRenderPass shadowRenderPass) {
     return true;
 }
 
-void M2Renderer::renderShadow(VkCommandBuffer cmd, const glm::mat4& lightSpaceMatrix, float globalTime) {
+void M2Renderer::renderShadow(VkCommandBuffer cmd, const glm::mat4& lightSpaceMatrix, float globalTime,
+                              const glm::vec3& shadowCenter, float shadowRadius) {
     if (!shadowPipeline_ || !shadowParamsSet_) return;
     if (instances.empty() || models.empty()) return;
 
     struct ShadowPush { glm::mat4 lightSpaceMatrix; glm::mat4 model; };
+    const float shadowRadiusSq = shadowRadius * shadowRadius;
 
     // Helper lambda to draw instances with a given foliageSway setting
     auto drawPass = [&](bool foliagePass) {
@@ -2641,6 +2643,10 @@ void M2Renderer::renderShadow(VkCommandBuffer cmd, const glm::mat4& lightSpaceMa
         const M2ModelGPU* currentModel = nullptr;
 
         for (const auto& instance : instances) {
+            // Distance cull against shadow frustum
+            glm::vec3 diff = instance.position - shadowCenter;
+            if (glm::dot(diff, diff) > shadowRadiusSq) continue;
+
             auto modelIt = models.find(instance.modelId);
             if (modelIt == models.end()) continue;
             const M2ModelGPU& model = modelIt->second;

src/rendering/wmo_renderer.cpp

@@ -1671,7 +1671,8 @@ bool WMORenderer::initializeShadow(VkRenderPass shadowRenderPass) {
     return true;
 }
 
-void WMORenderer::renderShadow(VkCommandBuffer cmd, const glm::mat4& lightSpaceMatrix) {
+void WMORenderer::renderShadow(VkCommandBuffer cmd, const glm::mat4& lightSpaceMatrix,
+                               const glm::vec3& shadowCenter, float shadowRadius) {
     if (!shadowPipeline_ || !shadowParamsSet_) return;
     if (instances.empty() || loadedModels.empty()) return;
 
@@ -1681,7 +1682,11 @@ void WMORenderer::renderShadow(VkCommandBuffer cmd, const glm::mat4& lightSpaceM
 
     struct ShadowPush { glm::mat4 lightSpaceMatrix; glm::mat4 model; };
 
+    const float shadowRadiusSq = shadowRadius * shadowRadius;
     for (const auto& instance : instances) {
+        // Distance cull against shadow frustum
+        glm::vec3 diff = instance.position - shadowCenter;
+        if (glm::dot(diff, diff) > shadowRadiusSq) continue;
         auto modelIt = loadedModels.find(instance.modelId);
         if (modelIt == loadedModels.end()) continue;
         const ModelData& model = modelIt->second;