创建图像

对于Vulkan来说，一组细化贴图的每一张图像需要使用不同的细化级别设置存储在VkImage对象中。细化级别设置为0的VkImage对象存储的是源图像，细化级别设置大于0的VkImage对象会被细化链引用使用。

细化级别是在创建VkImage对象时设置的，之前，我们一直将其设置为1。现在我们根据图像的尺寸来计算它。添加一个类成员变量来存储计算出的细化级别个数：

...
uint32_t mipLevels;
VkImage textureImage;
        ...

mipLevels成员变量的值可以在createTextureImage函数载入纹理图像时计算得到：

int texWidth, texHeight, texChannels;
stbi_uc* pixels = stbi_load(TEXTURE_PATH.c_str(), &texWidth, &texHeight, &texChannels, STBI_rgb_alpha);
        ...
mipLevels = static_cast<uint32_t>(std::floor(std::log2(std::max(texWidth, texHeight)))) + 1;

image

上面代码我们通过max函数来选择纹理尺寸中较大的那个，然后对其对以2为底的对数，并将结果向下取整后+1得到细化级别的个数，也就是mipLevels的值。

我们需要对createImage、createImageView和transitionImageLayout函数进行修改为它们添加mipLevels参数：

void createImage(uint32_t width, uint32_t height, uint32_t mipLevels, VkFormat format, VkImageTiling tiling, VkImageUsageFlags usage, VkMemoryPropertyFlags properties, VkImage& image, VkDeviceMemory& imageMemory) {
        ...
    imageInfo.mipLevels = mipLevels;
        ...
}

VkImageView createImageView(VkImage image, VkFormat format, VkImageAspectFlags aspectFlags, uint32_t mipLevels) {
        ...
    viewInfo.subresourceRange.levelCount = mipLevels;
        ...

void transitionImageLayout(VkImage image, VkFormat format,
VkImageLayout oldLayout, VkImageLayout newLayout, uint32_t mipLevels) {
        ...
    barrier.subresourceRange.levelCount = mipLevels;
        ...

更新对它们进行的调用，确保使用正确的参数进行调用：

createImage(swapChainExtent.width, swapChainExtent.height, 1,  depthFormat, VK_IMAGE_TILING_OPTIMAL, VK_IMAGE_USAGE_DEPTH_STENCIL_ATTACHMENT_BIT, VK_MEMORY_PROPERTY_DEVICE_LOCAL_BIT, depthImage, depthImageMemory);
        ...
createImage(texWidth, texHeight, mipLevels, VK_FORMAT_R8G8B8A8_UNORM, VK_IMAGE_TILING_OPTIMAL, VK_IMAGE_USAGE_TRANSFER_DST_BIT | VK_IMAGE_USAGE_SAMPLED_BIT, VK_MEMORY_PROPERTY_DEVICE_LOCAL_BIT, textureImage, textureImageMemory);

swapChainImageViews[i] = createImageView(swapChainImages[i], swapChainImageFormat, VK_IMAGE_ASPECT_COLOR_BIT, 1);
        ...
depthImageView = createImageView(depthImage, depthFormat, VK_IMAGE_ASPECT_DEPTH_BIT, 1);
        ...
textureImageView = createImageView(textureImage, VK_FORMAT_R8G8B8A8_UNORM, VK_IMAGE_ASPECT_COLOR_BIT, mipLevels);

transitionImageLayout(depthImage, depthFormat, VK_IMAGE_LAYOUT_UNDEFINED,
VK_IMAGE_LAYOUT_DEPTH_STENCIL_ATTACHMENT_OPTIMAL, 1);
        ...
    transitionImageLayout(textureImage, VK_FORMAT_R8G8B8A8_UNORM, VK_IMAGE_LAYOUT_UNDEFINED, VK_IMAGE_LAYOUT_TRANSFER_DST_OPTIMAL, mipLevels);