Background BLP texture pre-decoding + deferred WMO normal maps (12x streaming perf)

Move CPU-heavy BLP texture decoding from main thread to background worker
threads for all hot paths: terrain M2 models, WMO doodad M2s, WMO textures,
creature models, and gameobject WMOs. Each renderer (M2, WMO, Character) now
accepts a pre-decoded BLP cache that loadTexture() checks before falling back
to synchronous decode.

Defer WMO normal/height map generation (3 per-pixel passes: luminance, box
blur, Sobel) during terrain streaming finalization — this was the dominant
remaining bottleneck after BLP pre-decoding.

Terrain streaming stalls: 1576ms → 124ms worst case.

include/rendering/character_renderer.hpp

@@ -1,6 +1,7 @@
 #pragma once
 
 #include "pipeline/m2_loader.hpp"
+#include "pipeline/blp_loader.hpp"
 #include <vulkan/vulkan.h>
 #include <vk_mem_alloc.h>
 #include <glm/glm.hpp>
@@ -114,7 +115,11 @@ public:
     void setShadowMap(VkTexture*, const glm::mat4&) {}
     void clearShadowMap() {}
 
+    // Pre-decoded BLP cache: set before calling loadModel() to skip main-thread BLP decode
+    void setPredecodedBLPCache(std::unordered_map<std::string, pipeline::BLPImage>* cache) { predecodedBLPCache_ = cache; }
+
 private:
+    std::unordered_map<std::string, pipeline::BLPImage>* predecodedBLPCache_ = nullptr;
     // GPU representation of M2 model
     struct M2ModelGPU {
         VkBuffer vertexBuffer = VK_NULL_HANDLE;
@@ -180,6 +185,7 @@ private:
 
         // Bone update throttling (skip frames for distant characters)
         uint32_t boneUpdateCounter = 0;
+        const M2ModelGPU* cachedModel = nullptr;  // Avoid per-frame hash lookups
 
         // Per-instance bone SSBO (double-buffered per frame)
         VkBuffer boneBuffer[2] = {};

include/rendering/m2_renderer.hpp

@@ -1,6 +1,7 @@
 #pragma once
 
 #include "pipeline/m2_loader.hpp"
+#include "pipeline/blp_loader.hpp"
 #include <vulkan/vulkan.h>
 #include <vk_mem_alloc.h>
 #include <glm/glm.hpp>
@@ -188,6 +189,7 @@ struct M2Instance {
     bool skipCollision = false;    // WMO interior doodads — skip player wall collision
     float cachedBoundRadius = 0.0f;
     float portalSpinAngle = 0.0f;  // Accumulated spin angle for portal rotation
+    const M2ModelGPU* cachedModel = nullptr;  // Avoid per-frame hash lookups
 
     // Frame-skip optimization (update distant animations less frequently)
     uint8_t frameSkipCounter = 0;
@@ -328,6 +330,10 @@ public:
 
     std::vector<glm::vec3> getWaterVegetationPositions(const glm::vec3& camPos, float maxDist) const;
 
+    // Pre-decoded BLP cache: set by terrain manager before calling loadModel()
+    // so loadTexture() can skip the expensive assetManager->loadTexture() call.
+    void setPredecodedBLPCache(std::unordered_map<std::string, pipeline::BLPImage>* cache) { predecodedBLPCache_ = cache; }
+
 private:
     bool initialized_ = false;
     bool insideInterior = false;
@@ -414,6 +420,8 @@ private:
     uint32_t modelLimitRejectWarnings_ = 0;
 
     VkTexture* loadTexture(const std::string& path, uint32_t texFlags = 0);
+    std::unordered_map<std::string, pipeline::BLPImage>* predecodedBLPCache_ = nullptr;
+
     struct TextureCacheEntry {
         std::unique_ptr<VkTexture> texture;
         size_t approxBytes = 0;

include/rendering/terrain_manager.hpp

@@ -121,6 +121,12 @@ struct PendingTile {
     // Pre-loaded terrain texture BLP data (loaded on background thread to avoid
     // blocking file I/O on the main thread during finalizeTile)
     std::unordered_map<std::string, pipeline::BLPImage> preloadedTextures;
+
+    // Pre-decoded M2 model textures (decoded on background thread)
+    std::unordered_map<std::string, pipeline::BLPImage> preloadedM2Textures;
+
+    // Pre-decoded WMO textures (decoded on background thread)
+    std::unordered_map<std::string, pipeline::BLPImage> preloadedWMOTextures;
 };
 
 /**

include/rendering/vk_context.hpp

@@ -50,9 +50,12 @@ public:
     // Batch upload mode: records multiple upload commands into a single
     // command buffer, then submits with ONE fence wait instead of one per upload.
     void beginUploadBatch();
-    void endUploadBatch();
+    void endUploadBatch();       // Async: submits but does NOT wait for fence
+    void endUploadBatchSync();   // Sync: submits and waits (for load screens)
     bool isInUploadBatch() const { return inUploadBatch_; }
     void deferStagingCleanup(AllocatedBuffer staging);
+    void pollUploadBatches();    // Check completed async uploads, free staging buffers
+    void waitAllUploads();       // Block until all in-flight uploads complete
 
     // Accessors
     VkInstance getInstance() const { return instance; }
@@ -157,6 +160,14 @@ private:
     VkCommandBuffer batchCmd_ = VK_NULL_HANDLE;
     std::vector<AllocatedBuffer> batchStagingBuffers_;
 
+    // Async upload: in-flight batches awaiting GPU completion
+    struct InFlightBatch {
+        VkFence fence = VK_NULL_HANDLE;
+        VkCommandBuffer cmd = VK_NULL_HANDLE;
+        std::vector<AllocatedBuffer> stagingBuffers;
+    };
+    std::vector<InFlightBatch> inFlightBatches_;
+
     // Depth buffer (shared across all framebuffers)
     VkImage depthImage = VK_NULL_HANDLE;
     VkImageView depthImageView = VK_NULL_HANDLE;

include/rendering/wmo_renderer.hpp

@@ -1,5 +1,6 @@
 #pragma once
 
+#include "pipeline/blp_loader.hpp"
 #include <vulkan/vulkan.h>
 #include <vk_mem_alloc.h>
 #include <glm/glm.hpp>
@@ -325,6 +326,12 @@ public:
     // Pre-compute floor cache for all loaded WMO instances
     void precomputeFloorCache();
 
+    // Pre-decoded BLP cache: set before calling loadModel() to skip main-thread BLP decode
+    void setPredecodedBLPCache(std::unordered_map<std::string, pipeline::BLPImage>* cache) { predecodedBLPCache_ = cache; }
+
+    // Defer normal/height map generation during streaming to avoid CPU stalls
+    void setDeferNormalMaps(bool defer) { deferNormalMaps_ = defer; }
+
 private:
     // WMO material UBO — matches WMOMaterial in wmo.frag.glsl
     struct WMOMaterialUBO {
@@ -558,6 +565,7 @@ private:
      * Load a texture from path
      */
     VkTexture* loadTexture(const std::string& path);
+    std::unordered_map<std::string, pipeline::BLPImage>* predecodedBLPCache_ = nullptr;
 
     /**
      * Generate normal+height map from diffuse RGBA8 pixels
@@ -670,6 +678,7 @@ private:
 
     // Normal mapping / POM settings
     bool normalMappingEnabled_ = true;   // on by default
+    bool deferNormalMaps_ = false;       // skip normal map gen during streaming
     float normalMapStrength_ = 0.8f;     // 0.0 = flat, 1.0 = full, 2.0 = exaggerated
     bool pomEnabled_ = true;             // on by default
     int pomQuality_ = 1;                 // 0=Low(16), 1=Medium(32), 2=High(64)