Additional semaphore to synchronize offscreen and final render (Refs #70)

bloom/bloom.cpp

@@ -1185,18 +1185,38 @@ public:
 	{
 		VulkanExampleBase::prepareFrame();
 
-		// Gather command buffers to be sumitted to the queue
+		// The scene render command buffer has to wait for the offscreen
-		std::vector<VkCommandBuffer> submitCmdBuffers;
+		// rendering to be finished before we can use the framebuffer 
-		// Submit offscreen rendering command buffer 
+		// color image for sampling during final rendering
-		// todo : use event to ensure that offscreen result is finished bfore render command buffer is started
+		// To ensure this we use a dedicated offscreen synchronization
-		if (bloom)
+		// semaphore that will be signaled when offscreen renderin
-		{
+		// has been finished
-			submitCmdBuffers.push_back(offScreenCmdBuffer);
+		// This is necessary as an implementation may start both
-		}
+		// command buffers at the same time, there is no guarantee
-		submitCmdBuffers.push_back(drawCmdBuffers[currentBuffer]);
+		// that command buffers will be executed in the order they
-		submitInfo.commandBufferCount = submitCmdBuffers.size();
+		// have been submitted by the application
-		submitInfo.pCommandBuffers = submitCmdBuffers.data();
 
+		// Offscreen rendering
+
+		// Wait for swap chain presentation to finish
+		submitInfo.pWaitSemaphores = &semaphores.presentComplete;
+		// Signal ready with offscreen semaphore
+		submitInfo.pSignalSemaphores = &offscreenSemaphore;
+
+		// Submit work
+		submitInfo.commandBufferCount = 1;
+		submitInfo.pCommandBuffers = &offScreenCmdBuffer;
+		VK_CHECK_RESULT(vkQueueSubmit(queue, 1, &submitInfo, VK_NULL_HANDLE));
+
+		// Scene rendering
+
+		// Wait for offscreen semaphore
+		submitInfo.pWaitSemaphores = &offscreenSemaphore;
+		// Signal ready with render complete semaphpre
+		submitInfo.pSignalSemaphores = &semaphores.renderComplete;
+
+		// Submit work
+		submitInfo.pCommandBuffers = &drawCmdBuffers[currentBuffer];
 		VK_CHECK_RESULT(vkQueueSubmit(queue, 1, &submitInfo, VK_NULL_HANDLE));
 
 		VulkanExampleBase::submitFrame();