GPU Vulkan Display: don't recreate command buffer for mixing images

Author: davidrohr

GPU/GPUTracking/display/GPUDisplay.h

@@ -297,6 +297,7 @@ class GPUDisplay : public GPUDisplayInterface
   HighResTimer mAnimationTimer;
   int32_t mAnimationFrame = 0;
   int32_t mAnimationLastBase = 0;
+  int32_t mAnimationMixBase = -1; // Target keyframe of the current config blend (mixing), -1 = none
   int32_t mAnimateScreenshot = 0;
   int32_t mAnimationExport = 0;
   bool mAnimationChangeConfig = true;

GPU/GPUTracking/display/backend/GPUDisplayBackendVulkan.cxx

@@ -623,7 +623,7 @@ void GPUDisplayBackendVulkan::createCommandBuffers()
   allocInfo.commandPool = mCommandPool;
   allocInfo.level = vk::CommandBufferLevel::ePrimary;
   allocInfo.commandBufferCount = mImageCount;
-  mCommandBufferUpToDate.resize(mImageCount, false);
+  mCommandBufferUpToDate.assign(mImageCount, false);
   mCommandBuffers = mDevice.allocateCommandBuffers(allocInfo);
   mCommandBuffersText = mDevice.allocateCommandBuffers(allocInfo);
   mCommandBuffersTexture = mDevice.allocateCommandBuffers(allocInfo);
@@ -1471,7 +1471,7 @@ uint32_t GPUDisplayBackendVulkan::drawVertices(const vboList& v, const drawType
 
 bool GPUDisplayBackendVulkan::prepareDraw(const hmm_mat4& proj, const hmm_mat4& view, bool requestScreenshot, bool toMixBuffer, float includeMixImage)
 {
-  if (mDisplay->updateDrawCommands() || toMixBuffer || includeMixImage > 0) {
+  if (mDisplay->updateDrawCommands()) { // Main and mix command buffers stay cached while mixing, only the blend pass with the alpha value is recorded per frame
     needRecordCommandBuffers();
   }
 
@@ -1559,7 +1559,7 @@ void GPUDisplayBackendVulkan::finishDraw(bool doScreenshot, bool toMixBuffer, fl
 {
   if (!mCommandBufferUpToDate[mCurrentImageIndex]) {
     endFillCommandBuffer(mCurrentCommandBuffer);
-    if (!toMixBuffer && includeMixImage == 0.f) {
+    if (!toMixBuffer) { // The mix pass is recorded before the main pass of the same frame, both are valid only after the latter
       mCommandBufferUpToDate[mCurrentImageIndex] = true;
     }
   }

GPU/GPUTracking/display/backend/GPUDisplayBackendVulkan.h

@@ -152,8 +152,8 @@ class GPUDisplayBackendVulkan : public GPUDisplayBackend
   vk::PresentModeKHR mPresentMode;
   vk::SwapchainKHR mSwapChain;
   bool mMustUpdateSwapChain = false;
-  uint8_t mSwapChainSuboptimal = 0;  // Bitmasl if Last acquire / present / ... returned SUBOPTIMAL: recreate only on the first one
-  bool mFrameSkipped = false;        // No image acquired in this frame (timeout)
+  uint8_t mSwapChainSuboptimal = 0; // Bitmask if last acquire / present / ... returned SUBOPTIMAL: recreate only on the first one
+  bool mFrameSkipped = false;       // No image acquired in this frame (timeout)
   void handleSwapChainResult(vk::Result retVal, uint8_t suboptimalBit);
   std::vector<vk::Image> mSwapChainImages;
   std::vector<vk::ImageView> mSwapChainImageViews;
@@ -185,7 +185,7 @@ class GPUDisplayBackendVulkan : public GPUDisplayBackend
   std::vector<vk::CommandBuffer> mCommandBuffersMix;
   std::vector<vk::CommandBuffer> mCommandBuffersPresent;
   std::vector<vk::CommandBufferSubmitInfo> mFrameCommandBuffers; // All command buffers of the current frame, submitted as one batch, ordered by barriers
-  std::vector<bool> mCommandBufferUpToDate;
+  std::vector<bool> mCommandBufferUpToDate;                      // Per image: main and mix command buffers recorded and still valid (cached across frames), set after the main pass of the frame
   std::vector<vk::Semaphore> mImageAvailableSemaphore;
   std::vector<vk::Semaphore> mPresentSemaphore;
   vk::Semaphore mTimelineSemaphore;          // Signaled with an increasing value by every queue submit, replaces fences

GPU/GPUTracking/display/helpers/GPUDisplayAnimation.cxx

@@ -102,6 +102,7 @@ void GPUDisplay::startAnimation()
   mAnimationFrame = 0;
   mAnimate = 1;
   mAnimationLastBase = 0;
+  mAnimationMixBase = -1;
 }
 
 int32_t GPUDisplay::animateCamera(float& animateTime, float& mixSlaveImage, hmm_mat4& nextViewMatrix)
@@ -141,7 +142,12 @@ int32_t GPUDisplay::animateCamera(float& animateTime, float& mixSlaveImage, hmm_
       mAnimationLastBase = base - 1;
     }
 
-    if (base != mAnimationLastBase && mAnimateVectors[0][mAnimationLastBase] != mAnimateVectors[0][base] && memcmp(&mAnimateConfig[base], &mAnimateConfig[mAnimationLastBase], sizeof(mAnimateConfig[base]))) {
+    const bool mixing = base != mAnimationLastBase && mAnimateVectors[0][mAnimationLastBase] != mAnimateVectors[0][base] && memcmp(&mAnimateConfig[base], &mAnimateConfig[mAnimationLastBase], sizeof(mAnimateConfig[base]));
+    if ((mixing ? base : -1) != mAnimationMixBase) { // Blended configs changed: cached (Vulkan) command buffers must be re-recorded, otherwise they are kept while mixing
+      mAnimationMixBase = mixing ? base : -1;
+      mUpdateDrawCommands = true;
+    }
+    if (mixing) {
       mixSlaveImage = 1.f - (time - mAnimateVectors[0][mAnimationLastBase]) / (mAnimateVectors[0][base] - mAnimateVectors[0][mAnimationLastBase]);
       if (mixSlaveImage > 0) {
         mCfgL = mAnimateConfig[mAnimationLastBase];