fix(vulkan): defer resource frees until frame fence

include/rendering/vk_context.hpp

@@ -57,6 +57,15 @@ public:
     void pollUploadBatches();    // Check completed async uploads, free staging buffers
     void waitAllUploads();       // Block until all in-flight uploads complete
 
+    // Defer resource destruction until it is safe with multiple frames in flight.
+    //
+    // This queues work to run after the fence for the *current frame slot* has
+    // signaled the next time we enter beginFrame() for that slot (i.e. after
+    // MAX_FRAMES_IN_FLIGHT submissions). Use this for resources that may still
+    // be referenced by command buffers submitted in the previous frame(s),
+    // such as descriptor sets and buffers freed during streaming/unload.
+    void deferAfterFrameFence(std::function<void()>&& fn);
+
     // Accessors
     VkInstance getInstance() const { return instance; }
     VkPhysicalDevice getPhysicalDevice() const { return physicalDevice; }
@@ -173,6 +182,9 @@ private:
     };
     std::vector<InFlightBatch> inFlightBatches_;
 
+    void runDeferredCleanup(uint32_t frameIndex);
+    std::vector<std::function<void()>> deferredCleanup_[MAX_FRAMES_IN_FLIGHT];
+
     // Depth buffer (shared across all framebuffers)
     VkImage depthImage = VK_NULL_HANDLE;
     VkImageView depthImageView = VK_NULL_HANDLE;

src/rendering/terrain_renderer.cpp

@@ -990,42 +990,64 @@ void TerrainRenderer::clear() {
     }
     chunks.clear();
     renderedChunks = 0;
-
-    if (materialDescPool) {
-        vkResetDescriptorPool(vkCtx->getDevice(), materialDescPool, 0);
-    }
 }
 
 void TerrainRenderer::destroyChunkGPU(TerrainChunkGPU& chunk) {
+    if (!vkCtx) return;
+
+    VkDevice device = vkCtx->getDevice();
     VmaAllocator allocator = vkCtx->getAllocator();
 
-    if (chunk.vertexBuffer) {
-        AllocatedBuffer ab{}; ab.buffer = chunk.vertexBuffer; ab.allocation = chunk.vertexAlloc;
-        destroyBuffer(allocator, ab);
-        chunk.vertexBuffer = VK_NULL_HANDLE;
-    }
-    if (chunk.indexBuffer) {
-        AllocatedBuffer ab{}; ab.buffer = chunk.indexBuffer; ab.allocation = chunk.indexAlloc;
-        destroyBuffer(allocator, ab);
-        chunk.indexBuffer = VK_NULL_HANDLE;
-    }
-    if (chunk.paramsUBO) {
-        AllocatedBuffer ab{}; ab.buffer = chunk.paramsUBO; ab.allocation = chunk.paramsAlloc;
-        destroyBuffer(allocator, ab);
-        chunk.paramsUBO = VK_NULL_HANDLE;
-    }
-    // Return material descriptor set to the pool so it can be reused by new chunks
-    if (chunk.materialSet && materialDescPool) {
-        vkFreeDescriptorSets(vkCtx->getDevice(), materialDescPool, 1, &chunk.materialSet);
-    }
-    chunk.materialSet = VK_NULL_HANDLE;
+    // These resources may still be referenced by in-flight command buffers from
+    // previous frames. Defer actual destruction until this frame slot is safe.
+    ::VkBuffer vertexBuffer = chunk.vertexBuffer;
+    VmaAllocation vertexAlloc = chunk.vertexAlloc;
+    ::VkBuffer indexBuffer = chunk.indexBuffer;
+    VmaAllocation indexAlloc = chunk.indexAlloc;
+    ::VkBuffer paramsUBO = chunk.paramsUBO;
+    VmaAllocation paramsAlloc = chunk.paramsAlloc;
+    VkDescriptorPool pool = materialDescPool;
+    VkDescriptorSet materialSet = chunk.materialSet;
 
-    // Destroy owned alpha textures (VkTexture::~VkTexture is a no-op, must call destroy() explicitly)
-    VkDevice device = vkCtx->getDevice();
+    std::vector<VkTexture*> alphaTextures;
+    alphaTextures.reserve(chunk.ownedAlphaTextures.size());
     for (auto& tex : chunk.ownedAlphaTextures) {
-        if (tex) tex->destroy(device, allocator);
+        alphaTextures.push_back(tex.release());
     }
+
+    chunk.vertexBuffer = VK_NULL_HANDLE;
+    chunk.vertexAlloc = VK_NULL_HANDLE;
+    chunk.indexBuffer = VK_NULL_HANDLE;
+    chunk.indexAlloc = VK_NULL_HANDLE;
+    chunk.paramsUBO = VK_NULL_HANDLE;
+    chunk.paramsAlloc = VK_NULL_HANDLE;
+    chunk.materialSet = VK_NULL_HANDLE;
     chunk.ownedAlphaTextures.clear();
+
+    vkCtx->deferAfterFrameFence([device, allocator, vertexBuffer, vertexAlloc, indexBuffer, indexAlloc,
+                                 paramsUBO, paramsAlloc, pool, materialSet, alphaTextures]() {
+        if (vertexBuffer) {
+            AllocatedBuffer ab{}; ab.buffer = vertexBuffer; ab.allocation = vertexAlloc;
+            destroyBuffer(allocator, ab);
+        }
+        if (indexBuffer) {
+            AllocatedBuffer ab{}; ab.buffer = indexBuffer; ab.allocation = indexAlloc;
+            destroyBuffer(allocator, ab);
+        }
+        if (paramsUBO) {
+            AllocatedBuffer ab{}; ab.buffer = paramsUBO; ab.allocation = paramsAlloc;
+            destroyBuffer(allocator, ab);
+        }
+        if (materialSet && pool) {
+            VkDescriptorSet set = materialSet;
+            vkFreeDescriptorSets(device, pool, 1, &set);
+        }
+        for (VkTexture* tex : alphaTextures) {
+            if (!tex) continue;
+            tex->destroy(device, allocator);
+            delete tex;
+        }
+    });
 }
 
 int TerrainRenderer::getTriangleCount() const {

src/rendering/vk_context.cpp

@@ -55,6 +55,11 @@ void VkContext::shutdown() {
         vkDeviceWaitIdle(device);
     }
 
+    // With the device idle, it is safe to run any deferred per-frame cleanup.
+    for (uint32_t fi = 0; fi < MAX_FRAMES_IN_FLIGHT; fi++) {
+        runDeferredCleanup(fi);
+    }
+
     LOG_WARNING("VkContext::shutdown - destroyImGuiResources...");
     destroyImGuiResources();
 
@@ -103,6 +108,19 @@ void VkContext::shutdown() {
     LOG_WARNING("Vulkan context shutdown complete");
 }
 
+void VkContext::deferAfterFrameFence(std::function<void()>&& fn) {
+    deferredCleanup_[currentFrame].push_back(std::move(fn));
+}
+
+void VkContext::runDeferredCleanup(uint32_t frameIndex) {
+    auto& q = deferredCleanup_[frameIndex];
+    if (q.empty()) return;
+    for (auto& fn : q) {
+        if (fn) fn();
+    }
+    q.clear();
+}
+
 bool VkContext::createInstance(SDL_Window* window) {
     // Get required SDL extensions
     unsigned int sdlExtCount = 0;
@@ -1349,6 +1367,9 @@ VkCommandBuffer VkContext::beginFrame(uint32_t& imageIndex) {
         return VK_NULL_HANDLE;
     }
 
+    // Any work queued for this frame slot is now guaranteed to be unused by the GPU.
+    runDeferredCleanup(currentFrame);
+
     // Acquire next swapchain image
     VkResult result = vkAcquireNextImageKHR(device, swapchain, UINT64_MAX,
         frame.imageAvailableSemaphore, VK_NULL_HANDLE, &imageIndex);

src/rendering/water_renderer.cpp

@@ -1029,10 +1029,6 @@ void WaterRenderer::clear() {
         destroyWaterMesh(surface);
     }
     surfaces.clear();
-
-    if (vkCtx && materialDescPool) {
-        vkResetDescriptorPool(vkCtx->getDevice(), materialDescPool, 0);
-    }
 }
 
 // ==============================================================
@@ -1358,27 +1354,45 @@ void WaterRenderer::createWaterMesh(WaterSurface& surface) {
 
 void WaterRenderer::destroyWaterMesh(WaterSurface& surface) {
     if (!vkCtx) return;
+    VkDevice device = vkCtx->getDevice();
     VmaAllocator allocator = vkCtx->getAllocator();
 
-    if (surface.vertexBuffer) {
-        AllocatedBuffer ab{}; ab.buffer = surface.vertexBuffer; ab.allocation = surface.vertexAlloc;
-        destroyBuffer(allocator, ab);
+    ::VkBuffer vertexBuffer = surface.vertexBuffer;
+    VmaAllocation vertexAlloc = surface.vertexAlloc;
+    ::VkBuffer indexBuffer = surface.indexBuffer;
+    VmaAllocation indexAlloc = surface.indexAlloc;
+    ::VkBuffer materialUBO = surface.materialUBO;
+    VmaAllocation materialAlloc = surface.materialAlloc;
+    VkDescriptorPool pool = materialDescPool;
+    VkDescriptorSet materialSet = surface.materialSet;
+
     surface.vertexBuffer = VK_NULL_HANDLE;
-    }
-    if (surface.indexBuffer) {
-        AllocatedBuffer ab{}; ab.buffer = surface.indexBuffer; ab.allocation = surface.indexAlloc;
-        destroyBuffer(allocator, ab);
+    surface.vertexAlloc = VK_NULL_HANDLE;
     surface.indexBuffer = VK_NULL_HANDLE;
-    }
-    if (surface.materialUBO) {
-        AllocatedBuffer ab{}; ab.buffer = surface.materialUBO; ab.allocation = surface.materialAlloc;
-        destroyBuffer(allocator, ab);
+    surface.indexAlloc = VK_NULL_HANDLE;
     surface.materialUBO = VK_NULL_HANDLE;
-    }
-    if (surface.materialSet && materialDescPool) {
-        vkFreeDescriptorSets(vkCtx->getDevice(), materialDescPool, 1, &surface.materialSet);
-    }
+    surface.materialAlloc = VK_NULL_HANDLE;
     surface.materialSet = VK_NULL_HANDLE;
+
+    vkCtx->deferAfterFrameFence([device, allocator, vertexBuffer, vertexAlloc, indexBuffer, indexAlloc,
+                                 materialUBO, materialAlloc, pool, materialSet]() {
+        if (vertexBuffer) {
+            AllocatedBuffer ab{}; ab.buffer = vertexBuffer; ab.allocation = vertexAlloc;
+            destroyBuffer(allocator, ab);
+        }
+        if (indexBuffer) {
+            AllocatedBuffer ab{}; ab.buffer = indexBuffer; ab.allocation = indexAlloc;
+            destroyBuffer(allocator, ab);
+        }
+        if (materialUBO) {
+            AllocatedBuffer ab{}; ab.buffer = materialUBO; ab.allocation = materialAlloc;
+            destroyBuffer(allocator, ab);
+        }
+        if (materialSet && pool) {
+            VkDescriptorSet set = materialSet;
+            vkFreeDescriptorSets(device, pool, 1, &set);
+        }
+    });
 }
 
 // ==============================================================