Vulkan编程指南

纹理图像视图

在之前的交换链图像和帧缓冲章节，我们已经介绍过访问图像需要通过图像视图进行。对于纹理图像同样需要通过图像视图来进行访问。

添加一个类成员变量来存储纹理图像的图像视图对象，编写createTextureImageView函数来创建纹理图像的图像视图对象：

VkImageView textureImageView;

        ...

void initVulkan() {
        ...
createTextureImage();
createTextureImageView();
createVertexBuffer();
        ...
}

        ...

void createTextureImageView() {

}

createTextureImageView函数的实现可以由createImageViews函数修改得到。两者只有两处设置不同：format和image成员变量的设置。

VkImageViewCreateInfo viewInfo = {};
viewInfo.sType = VK_STRUCTURE_TYPE_IMAGE_VIEW_CREATE_INFO;
viewInfo.image = textureImage;
viewInfo.viewType = VK_IMAGE_VIEW_TYPE_2D;
viewInfo.format = VK_FORMAT_R8G8B8A8_UNORM;
viewInfo.subresourceRange.aspectMask = VK_IMAGE_ASPECT_COLOR_BIT;
viewInfo.subresourceRange.baseMipLevel = 0;
viewInfo.subresourceRange.levelCount = 1;
viewInfo.subresourceRange.baseArrayLayer = 0;
viewInfo.subresourceRange.layerCount = 1;

在这里，由于VK_COMPONENT_SWIZZLE_IDENTITY的值实际上是0，所以我们可以省略对viewInfo.components的显式初始化，将viewInfo.components的成员变量都设置为0。最后，调用vkCreateImageView函数创建图像视图对象：

if (vkCreateImageView(device, &viewInfo, nullptr, &textureImageView) != VK_SUCCESS) {
    throw std::runtime_error("failed to create texture image view!");
}

我们可以编写一个createImageView函数来简化图像视图对象的创建：

VkImageView createImageView(VkImage image, VkFormat format) {
    VkImageViewCreateInfo viewInfo = {};
    viewInfo.sType = VK_STRUCTURE_TYPE_IMAGE_VIEW_CREATE_INFO;
    viewInfo.image = image;
    viewInfo.viewType = VK_IMAGE_VIEW_TYPE_2D;
    viewInfo.format = format;
    viewInfo.subresourceRange.aspectMask = VK_IMAGE_ASPECT_COLOR_BIT;
    viewInfo.subresourceRange.baseMipLevel = 0;
    viewInfo.subresourceRange.levelCount = 1;
    viewInfo.subresourceRange.baseArrayLayer = 0;
    viewInfo.subresourceRange.layerCount = 1;

    VkImageView imageView;
    if (vkCreateImageView(device, &viewInfo, nullptr, &imageView) != VK_SUCCESS) {
        throw std::runtime_error("failed to create texture image view!");
    }

    return imageView;
}

现在我们可以使用createImageView函数来简化createTextureImageView的函数实现：

void createTextureImageView() {
    textureImageView = createImageView(textureImage, VK_FORMAT_R8G8B8A8_UNORM);
}

createImageViews的函数实现可以被简化为：

void createImageViews() {
    swapChainImageViews.resize(swapChainImages.size());

    for (uint32_t i = 0; i < swapChainImages.size(); i++) {
        swapChainImageViews[i] = createImageView(swapChainImages[i],
        swapChainImageFormat);
    }
}

应用程序结束前，我们需要在清除图像对象之前清除与之关联的图像视图对象：

void cleanup() {
    cleanupSwapChain();

    vkDestroyImageView(device, textureImageView, nullptr);

    vkDestroyImage(device, textureImage, nullptr);
    vkFreeMemory(device, textureImageMemory, nullptr);