最近调试UE4的vulkan的时候发现TileRendering有问题(多贴图复用同一个Sampler对象的时候有问题)。用frame debugger的时候发现贴图和素材对应关系不是很直观，所以从新记录一下两者的绑定方式。

vulkan的纹理映射

VkImage

vulkan中占用设备内存(显存)的类型有两种，分别是 Buffer 和 Image 。

在创建Image时需要制定多种参数。

typedef struct VkImageCreateInfo {
    VkStructureType          sType;
    const void*              pNext;
    VkImageCreateFlags       flags;
    VkImageType              imageType;
    VkFormat                 format;
    VkExtent3D               extent;
    uint32_t                 mipLevels;
    uint32_t                 arrayLayers;
    VkSampleCountFlagBits    samples;
    VkImageTiling            tiling;
    VkImageUsageFlags        usage;
    VkSharingMode            sharingMode;
    uint32_t                 queueFamilyIndexCount;
    const uint32_t*          pQueueFamilyIndices;
    VkImageLayout            initialLayout;
} VkImageCreateInfo;

VkImageCreateInfo文档

    void createImage(uint32_t width, uint32_t height, VkFormat format, VkImageTiling tiling, VkImageUsageFlags usage, VkMemoryPropertyFlags properties, VkImage& image, VkDeviceMemory& imageMemory) {
        VkImageCreateInfo imageInfo = {};
        imageInfo.sType = VK_STRUCTURE_TYPE_IMAGE_CREATE_INFO;
        imageInfo.imageType = VK_IMAGE_TYPE_2D;
        imageInfo.extent.width = width;
        imageInfo.extent.height = height;
        imageInfo.extent.depth = 1;
        imageInfo.mipLevels = 1;
        imageInfo.arrayLayers = 1;
        imageInfo.format = format;
        imageInfo.tiling = tiling;
        imageInfo.initialLayout = VK_IMAGE_LAYOUT_UNDEFINED;
        imageInfo.usage = usage;
        imageInfo.samples = VK_SAMPLE_COUNT_1_BIT;
        imageInfo.sharingMode = VK_SHARING_MODE_EXCLUSIVE;

        if (vkCreateImage(device, &imageInfo, nullptr, &image) != VK_SUCCESS) {
            throw std::runtime_error("failed to create image!");
        }

        VkMemoryRequirements memRequirements;
        vkGetImageMemoryRequirements(device, image, &memRequirements);

        VkMemoryAllocateInfo allocInfo = {};
        allocInfo.sType = VK_STRUCTURE_TYPE_MEMORY_ALLOCATE_INFO;
        allocInfo.allocationSize = memRequirements.size;
        allocInfo.memoryTypeIndex = findMemoryType(memRequirements.memoryTypeBits, properties);

        if (vkAllocateMemory(device, &allocInfo, nullptr, &imageMemory) != VK_SUCCESS) {
            throw std::runtime_error("failed to allocate image memory!");
        }

        vkBindImageMemory(device, image, imageMemory, 0);
    }

    VkImage textureImage;  // Global
    VkDeviceMemory textureImageMemory; // Global

    void createTextureImage() {
        int texWidth, texHeight, texChannels;
        stbi_uc* pixels = stbi_load("textures/texture.jpg", &texWidth, &texHeight, &texChannels, STBI_rgb_alpha);
        VkDeviceSize imageSize = texWidth * texHeight * 4;

        if (!pixels) {
            throw std::runtime_error("failed to load texture image!");
        }

        VkBuffer stagingBuffer;
        VkDeviceMemory stagingBufferMemory;
        createBuffer(imageSize, VK_BUFFER_USAGE_TRANSFER_SRC_BIT, VK_MEMORY_PROPERTY_HOST_VISIBLE_BIT | VK_MEMORY_PROPERTY_HOST_COHERENT_BIT, stagingBuffer, stagingBufferMemory);

        void* data;
        vkMapMemory(device, stagingBufferMemory, 0, imageSize, 0, &data);
            memcpy(data, pixels, static_cast<size_t>(imageSize));
        vkUnmapMemory(device, stagingBufferMemory);

        stbi_image_free(pixels);

        createImage(texWidth, texHeight, 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);

        transitionImageLayout(textureImage, VK_FORMAT_R8G8B8A8_UNORM, VK_IMAGE_LAYOUT_UNDEFINED, VK_IMAGE_LAYOUT_TRANSFER_DST_OPTIMAL);
            copyBufferToImage(stagingBuffer, textureImage, static_cast<uint32_t>(texWidth), static_cast<uint32_t>(texHeight));
        transitionImageLayout(textureImage, VK_FORMAT_R8G8B8A8_UNORM, VK_IMAGE_LAYOUT_TRANSFER_DST_OPTIMAL, VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL);

        vkDestroyBuffer(device, stagingBuffer, nullptr);
        vkFreeMemory(device, stagingBufferMemory, nullptr);
    }

image view

ImageView是指向某个特定Image的一组参数。Vulkan使用ImageView而不是直接使用Image。ImageView表示Image子资源的一段连续范围，以及相关的元数据(eg: 通过ImageView可以访问Image的某个特定的MIP level)

typedef struct VkImageViewCreateInfo {
    VkStructureType            sType;
    const void*                pNext;
    VkImageViewCreateFlags     flags;
    VkImage                    image;
    VkImageViewType            viewType;
    VkFormat                   format;
    VkComponentMapping         components;
    VkImageSubresourceRange    subresourceRange;
} VkImageViewCreateInfo;

VkImageViewCreateInfo文档

    VkImageView textureImageView; // Global

    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;
    }

Sampler

Sampler并不和某个特定的Image相关联，只是一组状态参数，比如filtering mode (nearest or linear) 或者 addressing mode (repeat, clamp-to-edge, clamp-to-border etc.).

typedef struct VkSamplerCreateInfo {
    VkStructureType         sType;
    const void*             pNext;
    VkSamplerCreateFlags    flags;
    VkFilter                magFilter;
    VkFilter                minFilter;
    VkSamplerMipmapMode     mipmapMode;
    VkSamplerAddressMode    addressModeU;
    VkSamplerAddressMode    addressModeV;
    VkSamplerAddressMode    addressModeW;
    float                   mipLodBias;
    VkBool32                anisotropyEnable;
    float                   maxAnisotropy;
    VkBool32                compareEnable;
    VkCompareOp             compareOp;
    float                   minLod;
    float                   maxLod;
    VkBorderColor           borderColor;
    VkBool32                unnormalizedCoordinates;
} VkSamplerCreateInfo;

VkSamplerCreateInfo文档

    VkSampler textureSampler; // Global

    void createTextureSampler() {
        VkSamplerCreateInfo samplerInfo = {};
        samplerInfo.sType = VK_STRUCTURE_TYPE_SAMPLER_CREATE_INFO;
        samplerInfo.magFilter = VK_FILTER_LINEAR;
        samplerInfo.minFilter = VK_FILTER_LINEAR;
        samplerInfo.addressModeU = VK_SAMPLER_ADDRESS_MODE_REPEAT;
        samplerInfo.addressModeV = VK_SAMPLER_ADDRESS_MODE_REPEAT;
        samplerInfo.addressModeW = VK_SAMPLER_ADDRESS_MODE_REPEAT;
        samplerInfo.anisotropyEnable = VK_TRUE;
        samplerInfo.maxAnisotropy = 16;
        samplerInfo.borderColor = VK_BORDER_COLOR_INT_OPAQUE_BLACK;
        samplerInfo.unnormalizedCoordinates = VK_FALSE;
        samplerInfo.compareEnable = VK_FALSE;
        samplerInfo.compareOp = VK_COMPARE_OP_ALWAYS;
        samplerInfo.mipmapMode = VK_SAMPLER_MIPMAP_MODE_LINEAR;

        if (vkCreateSampler(device, &samplerInfo, nullptr, &textureSampler) != VK_SUCCESS) {
            throw std::runtime_error("failed to create texture sampler!");
        }
    }

将Image view还有Sampler关联

在创建 DescriptorSet 的时候完成Image view还有Sampler关联。DescriptorSet 可以理解为Uniform变量的集合。共有两种，分别是 Buffer 和 Image。

    void createDescriptorSet() {
        VkDescriptorSetLayout layouts[] = {descriptorSetLayout};
        VkDescriptorSetAllocateInfo allocInfo = {};
        allocInfo.sType = VK_STRUCTURE_TYPE_DESCRIPTOR_SET_ALLOCATE_INFO;
        allocInfo.descriptorPool = descriptorPool;
        allocInfo.descriptorSetCount = 1;
        allocInfo.pSetLayouts = layouts;

        if (vkAllocateDescriptorSets(device, &allocInfo, &descriptorSet) != VK_SUCCESS) {
            throw std::runtime_error("failed to allocate descriptor set!");
        }

        VkDescriptorBufferInfo bufferInfo = {};
        bufferInfo.buffer = uniformBuffer;
        bufferInfo.offset = 0;
        bufferInfo.range = sizeof(UniformBufferObject);

        VkDescriptorImageInfo imageInfo = {};
        imageInfo.imageLayout = VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL;
        imageInfo.imageView = textureImageView;
        imageInfo.sampler = textureSampler;

        std::array<VkWriteDescriptorSet, 2> descriptorWrites = {};

        descriptorWrites[0].sType = VK_STRUCTURE_TYPE_WRITE_DESCRIPTOR_SET;
        descriptorWrites[0].dstSet = descriptorSet;
        descriptorWrites[0].dstBinding = 0;
        descriptorWrites[0].dstArrayElement = 0;
        descriptorWrites[0].descriptorType = VK_DESCRIPTOR_TYPE_UNIFORM_BUFFER;
        descriptorWrites[0].descriptorCount = 1;
        descriptorWrites[0].pBufferInfo = &bufferInfo;

        descriptorWrites[1].sType = VK_STRUCTURE_TYPE_WRITE_DESCRIPTOR_SET;
        descriptorWrites[1].dstSet = descriptorSet;
        descriptorWrites[1].dstBinding = 1;
        descriptorWrites[1].dstArrayElement = 0;
        descriptorWrites[1].descriptorType = VK_DESCRIPTOR_TYPE_COMBINED_IMAGE_SAMPLER;
        descriptorWrites[1].descriptorCount = 1;
        descriptorWrites[1].pImageInfo = &imageInfo;

        vkUpdateDescriptorSets(device, static_cast<uint32_t>(descriptorWrites.size()), descriptorWrites.data(), 0, nullptr);
    }

上面的代码创建了两个DescriptorSet，0位置的表示layout(binding = 0)的uniform变量，在本程序中为MVP矩阵。1位置表示layout(binding = 1)的uniform变量，在本例中为sampler2D。VkDescriptorImageInfo中完成Image view和sampler的关联。

程序完整代码c++ code，Vertex shader，Fragment shader。