Correct pose of Vulkan open feature

当我们在用VulkanWhen writing some applications,Whether using its graphics pipeline or computational pipeline,More or less need to use some current equipmentVulkanExtended features not available in the core version,So how can we enable some of the features we need both safely and conveniently？This article will give you an introduction.

There are basically two ways to enable an extended feature of the current device.And the two approaches are not mutually exclusive,but need to be used together.

一、Specify a specific extension

This is a common and commonly used method.我们先调用 vkEnumerateDeviceExtensionProperties APIEnumerates the currently specified use 物理设备 How many extensions are supported in total,最后在创建 逻辑设备 When specifying the extension that needs to be used VkDeviceCreateInfo 结构体对象的 ppEnabledExtensionNames 成员之中.
Below is a rough sample code for enumerating extensions：

enum MY_CONSTANT
{
    
    MAX_VULKAN_GLOBAL_EXT_PROPS = 256
};

    // Query Vulkan extensions the current selected physical device supports
    uint32_t extPropCount = 0U;
    res = vkEnumerateDeviceExtensionProperties(physicalDevices[deviceIndex], NULL, &extPropCount, NULL);
    if (res != VK_SUCCESS)
    {
    
        printf("vkEnumerateDeviceExtensionProperties for count failed: %d\n", res);
        return res;
    }
    printf("The current selected physical device supports %u Vulkan extensions!\n", extPropCount);
    if (extPropCount > MAX_VULKAN_GLOBAL_EXT_PROPS) {
    
        extPropCount = MAX_VULKAN_GLOBAL_EXT_PROPS;
    }

    VkExtensionProperties extProps[MAX_VULKAN_GLOBAL_EXT_PROPS];
    res = vkEnumerateDeviceExtensionProperties(physicalDevices[deviceIndex], NULL, &extPropCount, extProps);
    if (res != VK_SUCCESS)
    {
    
        printf("vkEnumerateDeviceExtensionProperties for content failed: %d\n", res);
        return res;
    }

这里各位需要注意的是,Some extensions may be currentVulkanThe version has been integrated into the core,而有些GPUThe designer may no longer list the extension,因此我们用 vkEnumerateDeviceExtensionProperties 这一APIcan't be counted at all,But that doesn't mean we can't use the extension.

For example, our current device may not be enumerated VK_KHR_8BIT_STORAGE_EXTENSION_NAME 这一特征,But the feature was earlierVulkan 1.2The version has been added to the core.此时,We can go through what will be described below,Use its corresponding feature structure for further query.And the feature name happens to have a feature structure,名字为：VkPhysicalDevice8BitStorageFeatures.

另外,For some extensions without corresponding feature structures,You can also use its corresponding attribute structure to query.比如,If our current device is not enumerated VK_EXT_SHADER_SUBGROUP_VOTE_EXTENSION_NAME 这一特征,Then we can followsubgroup相关的 VkPhysicalDeviceSubgroupProperties in this property supportedOperations Do further enquiries.

We'll talk about it belowVulkanHow to query and open the feature through the feature structure.