[译]Vulkan教程(17)帧缓存

[译]Vulkan教程(17)帧缓存

Framebuffers 帧缓存

We've talked a lot about framebuffers in the past few chapters and we've set up the render pass to expect a single framebuffer with the same format as the swap chain images, but we haven't actually created any yet.

我们在过去的章节谈论过很多次帧缓存了，我们已经设置了render pass，希望有一个帧缓存with与交换链image相同的格式，但是我们还没有创建帧缓存。

The attachments specified during render pass creation are bound by wrapping them into a VkFramebuffer object. A framebuffer object references all of the VkImageView objects that represent the attachments. In our case that will be only a single one: the color attachment. However, the image that we have to use for the attachment depends on which image the swap chain returns when we retrieve one for presentation. That means that we have to create a framebuffer for all of the images in the swap chain and use the one that corresponds to the retrieved image at drawing time.

在创建render pass时指定的附件，通过一个VkFramebuffer 对象关联起来。帧缓存对象引用所有的VkImageView 对象that代表附件。在我们的案例中只有1个，即颜色附件。但是，用作附件的image依赖于交换链返回哪个image when我们检索一个for呈现。这意味着，我们必须创建一个帧缓存for交换链的每个image，在绘制时使用与检索到的image对应的那个帧缓存。

To that end, create another std::vector class member to hold the framebuffers:

为此，创建另一个类成员std::vector  to记录这些帧缓存。

std::vector<VkFramebuffer> swapChainFramebuffers;

We'll create the objects for this array in a new function createFramebuffers that is called from initVulkan right after creating the graphics pipeline:

我们将为此数组创建对象在新函数createFramebuffers that被initVulkan 调用after创建图形管道：

void initVulkan() {
    createInstance();
    setupDebugCallback();
    createSurface();
    pickPhysicalDevice();
    createLogicalDevice();
    createSwapChain();
    createImageViews();
    createRenderPass();
    createGraphicsPipeline();
    createFramebuffers();
}
 
...
 
void createFramebuffers() {
 
}

Start by resizing the container to hold all of the framebuffers:

开始，调整容器大小to记录所有的帧缓存：

void createFramebuffers() {
    swapChainFramebuffers.resize(swapChainImageViews.size());
}

We'll then iterate through the image views and create framebuffers from them:

然后我们遍历image视图，为它们创建帧缓存：

for (size_t i = 0; i < swapChainImageViews.size(); i++) {
    VkImageView attachments[] = {
        swapChainImageViews[i]
    };
 
    VkFramebufferCreateInfo framebufferInfo = {};
    framebufferInfo.sType = VK_STRUCTURE_TYPE_FRAMEBUFFER_CREATE_INFO;
    framebufferInfo.renderPass = renderPass;
    framebufferInfo.attachmentCount = 1;
    framebufferInfo.pAttachments = attachments;
    framebufferInfo.width = swapChainExtent.width;
    framebufferInfo.height = swapChainExtent.height;
    framebufferInfo.layers = 1;
 
    if (vkCreateFramebuffer(device, &framebufferInfo, nullptr, &swapChainFramebuffers[i]) != VK_SUCCESS) {
        throw std::runtime_error("failed to create framebuffer!");
    }
}

As you can see, creation of framebuffers is quite straightforward. We first need to specify with which renderPassthe framebuffer needs to be compatible. You can only use a framebuffer with the render passes that it is compatible with, which roughly means that they use the same number and type of attachments.

如你所见，帧缓存的创建过程是十分直观的。我们首先要指定帧缓存需要与哪个renderPass兼容。你只能用与render pass兼容的帧缓存，基本上意思是它们的附件的数量和类型相同。

The attachmentCount and pAttachments parameters specify the VkImageView objects that should be bound to the respective attachment descriptions in the render pass pAttachment array.

attachmentCount 和pAttachments 参数指定VkImageView 对象that应当被绑定到相应的附件描述信息in render pass pAttachment 数组。

The width and height parameters are self-explanatory and layers refers to the number of layers in image arrays. Our swap chain images are single images, so the number of layers is 1.

width 和height 参数是不言自明的，layers 指image数组中的layer的数量。我们的交换链image是单image，所以layer数量为1。

We should delete the framebuffers before the image views and render pass that they are based on, but only after we've finished rendering:

我们应当在删除image视图和render pass之前删除帧缓存，但是要在完成渲染之后：

void cleanup() {
    for (auto framebuffer : swapChainFramebuffers) {
        vkDestroyFramebuffer(device, framebuffer, nullptr);
    }
 
    ...
}

We've now reached the milestone where we have all of the objects that are required for rendering. In the next chapter we're going to write the first actual drawing commands.

我们现在到达了一个里程碑where我们有了所有的对象that被要求用于渲染。下一章我们要写第一个实际的绘制命令。

C++ code / Vertex shader / Fragment shader

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