Additional semaphore to synchronize offscreen and final render

shadowmappingomni/shadowmappingomni.cpp

@@ -121,6 +121,9 @@ public:
 	VkCommandBuffer offScreenCmdBuffer = VK_NULL_HANDLE;
 	VkFormat fbDepthFormat;
 
+	// Semaphore used to synchronize offscreen rendering before using it's texture target for sampling
+	VkSemaphore offscreenSemaphore = VK_NULL_HANDLE;
+
 	VulkanExample() : VulkanExampleBase(ENABLE_VALIDATION)
 	{
 		zoom = -175.0f;
@@ -177,6 +180,7 @@ public:
 		vkTools::destroyUniformData(device, &uniformData.scene);
 
 		vkFreeCommandBuffers(device, cmdPool, 1, &offScreenCmdBuffer);
+		vkDestroySemaphore(device, offscreenSemaphore, nullptr);
 	}
 
 	void prepareCubeMap()
@@ -487,33 +491,23 @@ public:
 	// Command buffer for rendering and copying all cube map faces
 	void buildOffscreenCommandBuffer()
 	{
-		// Create separate command buffer for offscreen 
-		// rendering
 		if (offScreenCmdBuffer == VK_NULL_HANDLE)
 		{
-			VkCommandBufferAllocateInfo cmd = vkTools::initializers::commandBufferAllocateInfo(
+			offScreenCmdBuffer = VulkanExampleBase::createCommandBuffer(VK_COMMAND_BUFFER_LEVEL_PRIMARY, false);
-				cmdPool,
-				VK_COMMAND_BUFFER_LEVEL_PRIMARY,
-				1);
-			VK_CHECK_RESULT(vkAllocateCommandBuffers(device, &cmd, &offScreenCmdBuffer));
 		}
 
+		// Create a semaphore used to synchronize offscreen rendering and usage
+		VkSemaphoreCreateInfo semaphoreCreateInfo = vkTools::initializers::semaphoreCreateInfo();
+		VK_CHECK_RESULT(vkCreateSemaphore(device, &semaphoreCreateInfo, nullptr, &offscreenSemaphore));
+
 		VkCommandBufferBeginInfo cmdBufInfo = vkTools::initializers::commandBufferBeginInfo();
 
 		VK_CHECK_RESULT(vkBeginCommandBuffer(offScreenCmdBuffer, &cmdBufInfo));
 
-		VkViewport viewport = vkTools::initializers::viewport(
+		VkViewport viewport = vkTools::initializers::viewport((float)offScreenFrameBuf.width, (float)offScreenFrameBuf.height, 0.0f, 1.0f);
-			(float)offScreenFrameBuf.width,
-			(float)offScreenFrameBuf.height,
-			0.0f,
-			1.0f);
 		vkCmdSetViewport(offScreenCmdBuffer, 0, 1, &viewport);
 
-		VkRect2D scissor = vkTools::initializers::rect2D(
+		VkRect2D scissor = vkTools::initializers::rect2D(offScreenFrameBuf.width, offScreenFrameBuf.height,	0, 0);
-			offScreenFrameBuf.width,
-			offScreenFrameBuf.height,
-			0,
-			0);
 		vkCmdSetScissor(offScreenCmdBuffer, 0, 1, &scissor);
 
 		VkImageSubresourceRange subresourceRange = {};
@@ -1003,16 +997,32 @@ public:
 	{
 		VulkanExampleBase::prepareFrame();
 
-		// Submit offscreen rendering command buffer 
+		// The scene render command buffer has to wait for the offscreen
-		// todo : use event to ensure that offscreen result is finished bfore render command buffer is started
+		// rendering (and transfer) to be finished before using
-		std::vector<VkCommandBuffer> submitCmdBuffers = {
+		// the shadow map, so we need to synchronize
-			offScreenCmdBuffer,
+		// We use an additional semaphore for this
-			drawCmdBuffers[currentBuffer],
-		};
-		submitCmdBuffers.push_back(drawCmdBuffers[currentBuffer]);
-		submitInfo.commandBufferCount = submitCmdBuffers.size();
-		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();