在另一个之上使用一个渲染通道

Question

我正在尝试在我的应用程序中实现 imGUI，它已经有一些用于渲染网格的渲染通道。它的命令缓冲区仅在新网格添加到场景时更新，而 imGUI 命令缓冲区应每帧更新。辅助命令缓冲区不适合我，因为我总是必须从不经常更新的主 cb 中引用它。

我还想提一下，我的代码基于this 教程。

我得出的结论是，我应该有两个渲染通道和两个主命令缓冲区。现在唯一的问题是我无法合并这两个渲染通道。

有main rp的代码：

    vk::AttachmentDescription colorAttachment;
    colorAttachment.format = swapChainImageFormat;
    colorAttachment.samples = vk::SampleCountFlagBits::e1;
    colorAttachment.loadOp = vk::AttachmentLoadOp::eClear;
    colorAttachment.storeOp = vk::AttachmentStoreOp::eStore;
    colorAttachment.stencilLoadOp = vk::AttachmentLoadOp::eDontCare;
    colorAttachment.stencilStoreOp = vk::AttachmentStoreOp::eNoneQCOM;
    colorAttachment.initialLayout = vk::ImageLayout::eUndefined;
    colorAttachment.finalLayout = vk::ImageLayout::ePresentSrcKHR;
     
    vk::AttachmentDescription depthAttachment;
    depthAttachment.format = FindDepthFormat();
    depthAttachment.samples = vk::SampleCountFlagBits::e1;
    depthAttachment.loadOp = vk::AttachmentLoadOp::eClear;
    depthAttachment.storeOp = vk::AttachmentStoreOp::eDontCare;
    depthAttachment.stencilLoadOp = vk::AttachmentLoadOp::eDontCare;
    depthAttachment.stencilStoreOp = vk::AttachmentStoreOp::eDontCare;
    depthAttachment.initialLayout = vk::ImageLayout::eUndefined;
    depthAttachment.finalLayout = vk::ImageLayout::eDepthStencilAttachmentOptimal;
     
    std::array<vk::AttachmentDescription, 2> attachments = { colorAttachment, depthAttachment };
     
    vk::AttachmentReference colorAttachmentRef;
    colorAttachmentRef.attachment = 0;
    colorAttachmentRef.layout = vk::ImageLayout::eColorAttachmentOptimal;
     
    vk::AttachmentReference depthAttachmentRef;
    depthAttachmentRef.attachment = 1;
    depthAttachmentRef.layout = vk::ImageLayout::eDepthStencilAttachmentOptimal;
     
    vk::SubpassDescription subpass;
    subpass.colorAttachmentCount = 1;
    subpass.pColorAttachments = &colorAttachmentRef;
    subpass.pDepthStencilAttachment = &depthAttachmentRef;
     
    vk::SubpassDependency dependency;
    dependency.srcSubpass = VK_SUBPASS_EXTERNAL;
    dependency.dstSubpass = 0;
    dependency.srcStageMask = vk::PipelineStageFlagBits::eColorAttachmentOutput;
    dependency.srcAccessMask = vk::AccessFlagBits();
    dependency.dstStageMask = vk::PipelineStageFlagBits::eColorAttachmentOutput;
    dependency.dstAccessMask = vk::AccessFlagBits::eColorAttachmentRead | vk::AccessFlagBits::eColorAttachmentWrite;
     
    vk::RenderPassCreateInfo renderPassInfo;
    renderPassInfo.attachmentCount = static_cast<uint32_t>(attachments.size());
    renderPassInfo.pAttachments = attachments.data();
    renderPassInfo.subpassCount = 1;
    renderPassInfo.pSubpasses = &subpass;
    renderPassInfo.dependencyCount = 1;
    renderPassInfo.pDependencies = &dependency;
     
    gameRenderPass = device.createRenderPass(renderPassInfo);

有ui rp的代码：

vk::AttachmentDescription colorAttachment;
colorAttachment.format = swapChainImageFormat;
colorAttachment.samples = vk::SampleCountFlagBits::e1;
colorAttachment.loadOp = vk::AttachmentLoadOp::eLoad;
colorAttachment.storeOp = vk::AttachmentStoreOp::eStore;
colorAttachment.stencilLoadOp = vk::AttachmentLoadOp::eDontCare;
colorAttachment.stencilStoreOp = vk::AttachmentStoreOp::eDontCare;
colorAttachment.initialLayout = vk::ImageLayout::ePresentSrcKHR;
colorAttachment.finalLayout = vk::ImageLayout::ePresentSrcKHR;

vk::AttachmentDescription depthAttachment;
depthAttachment.format = FindDepthFormat();
depthAttachment.samples = vk::SampleCountFlagBits::e1;
depthAttachment.loadOp = vk::AttachmentLoadOp::eClear;
depthAttachment.storeOp = vk::AttachmentStoreOp::eDontCare;
depthAttachment.stencilLoadOp = vk::AttachmentLoadOp::eDontCare;
depthAttachment.stencilStoreOp = vk::AttachmentStoreOp::eDontCare;
depthAttachment.initialLayout = vk::ImageLayout::eUndefined;
depthAttachment.finalLayout = vk::ImageLayout::eDepthStencilAttachmentOptimal;

std::array<vk::AttachmentDescription, 2> attachments = { colorAttachment, depthAttachment };
  
vk::AttachmentReference colorAttachmentRef;
colorAttachmentRef.attachment = 0;
colorAttachmentRef.layout = vk::ImageLayout::eColorAttachmentOptimal;

vk::AttachmentReference depthAttachmentRef;
depthAttachmentRef.attachment = 1;
depthAttachmentRef.layout = vk::ImageLayout::eDepthStencilAttachmentOptimal;

vk::SubpassDescription subpass;
subpass.colorAttachmentCount = 1;
subpass.pColorAttachments = &colorAttachmentRef;
subpass.pDepthStencilAttachment = &depthAttachmentRef;

vk::SubpassDependency dependency;
dependency.srcSubpass = VK_SUBPASS_EXTERNAL;
dependency.dstSubpass = 0;
dependency.srcStageMask = vk::PipelineStageFlagBits::eColorAttachmentOutput;
dependency.srcAccessMask = vk::AccessFlagBits();
dependency.dstStageMask = vk::PipelineStageFlagBits::eColorAttachmentOutput;
dependency.dstAccessMask = vk::AccessFlagBits::eColorAttachmentRead | vk::AccessFlagBits::eColorAttachmentWrite;

vk::RenderPassCreateInfo renderPassInfo;
renderPassInfo.attachmentCount = static_cast<uint32_t>(attachments.size());
renderPassInfo.pAttachments = attachments.data();
renderPassInfo.subpassCount = 1;
renderPassInfo.pSubpasses = &subpass;
renderPassInfo.dependencyCount = 1;
renderPassInfo.pDependencies = &dependency;

uiRenderPass = device.createRenderPass(renderPassInfo);

还有我的 DrawFrame 函数的代码：

device.waitForFences(1, &inFlightFences[currentFrame], true, UINT64_MAX);

uint32_t imageIndex;
device.acquireNextImageKHR(swapChain, UINT64_MAX, imageAvailableSemaphores[currentFrame], nullptr, &imageIndex);

if (imagesInFlight[imageIndex].operator!=(nullptr))
{
  device.waitForFences(1, &imagesInFlight[imageIndex], true, UINT64_MAX);
}
imagesInFlight[imageIndex] = inFlightFences[currentFrame];

vk::SubmitInfo submitInfo;

vk::Semaphore waitSemaphores[] = { imageAvailableSemaphores[currentFrame] };
vk::PipelineStageFlags waitStages[] = { vk::PipelineStageFlagBits::eColorAttachmentOutput };
submitInfo.waitSemaphoreCount = 1;
submitInfo.pWaitSemaphores = waitSemaphores;
submitInfo.pWaitDstStageMask = waitStages;

vk::Semaphore signalSemaphores[] = { renderFinishedSemaphores[currentFrame] };
submitInfo.signalSemaphoreCount = 1;
submitInfo.pSignalSemaphores = signalSemaphores;

device.resetFences(1, &inFlightFences[currentFrame]);

UpdateUniformBuffer(imageIndex);

UpdateUiCommandBuffer(imageIndex);

if (comandUpdateRequired[imageIndex])
{
  UpdateGameCommandBuffer(imageIndex);
  comandUpdateRequired[imageIndex] = false;
}

std::vector<vk::CommandBuffer> commands = { gameCommandBuffers[imageIndex], uiCommandBuffers[imageIndex] };
  
submitInfo.commandBufferCount = static_cast<uint32_t>(commands.size());
submitInfo.pCommandBuffers = commands.data();

graphicsQueue.submit(1, &submitInfo, inFlightFences[currentFrame]);

vk::PresentInfoKHR presentInfo;
presentInfo.waitSemaphoreCount = 1;
presentInfo.pWaitSemaphores = signalSemaphores;

vk::SwapchainKHR swapChains[] = { swapChain };
presentInfo.swapchainCount = 1;
presentInfo.pSwapchains = swapChains;
presentInfo.pImageIndices = &imageIndex;

presentQueue.presentKHR(presentInfo);

presentQueue.waitIdle();

currentFrame = (currentFrame + 1) % MAX_FRAMES_IN_FLIGHT;

结果是：

如您所见，清晰的颜色用于覆盖我第一次渲染过程的结果，这不是我想要的。

请注意，load 和 store 操作已在使用中，但它仍然不起作用。

---

更新

有我第二个cb的代号：

device.freeCommandBuffers(commandPool, 1, &uiCommandBuffers[index]);

vk::CommandBufferAllocateInfo allocInfo;
allocInfo.commandPool = commandPool;
allocInfo.level = vk::CommandBufferLevel::ePrimary;
allocInfo.commandBufferCount = 1;

device.allocateCommandBuffers(&allocInfo, &uiCommandBuffers[index]);

vk::CommandBufferBeginInfo beginInfo;

uiCommandBuffers[index].begin(beginInfo);

std::array<vk::ClearValue, 2> clearValues;
clearValues[0].color = vk::ClearColorValue(std::array<float, 4>{ 1.0f, 0.0f, 0.0f, 1.0f });
clearValues[1].depthStencil = { 1.0f, 0 };

vk::RenderPassBeginInfo renderPassInfo;
renderPassInfo.renderPass = gameRenderPass;
renderPassInfo.framebuffer = uiSwapChainFramebuffers[index];
renderPassInfo.renderArea.offset = { 0, 0 };
renderPassInfo.renderArea.extent = swapChainExtent;
renderPassInfo.clearValueCount = static_cast<uint32_t>(clearValues.size()); // It doesn't work at all if I set clear values count to 0
renderPassInfo.pClearValues = clearValues.data();
//renderPassInfo.clearValueCount = 0;
//renderPassInfo.pClearValues = nullptr;

uiCommandBuffers[index].beginRenderPass(renderPassInfo, vk::SubpassContents::eInline);

auto drawData = ImGui::GetDrawData();
if (drawData)
{
    ImGui_ImplVulkan_RenderDrawData(drawData, uiCommandBuffers[index]);
}

uiCommandBuffers[index].endRenderPass();

uiCommandBuffers[index].end();

Answer 1

如果您想使用第二次渲染渲染 UI，只需将第一次渲染中颜色附件的storeOp 设置为VK_ATTACHMENT_STORE_OP_STORE，并将第二次渲染中的loadOp 设置为VK_ATTACHMENT_LOAD_OP_LOAD保留内容。

另一种选择是在单个渲染过程中执行此操作，就像我在示例中所做的那样。只需渲染您的场景，并将 UI 的绘制调用放在同一个渲染通道中。