vulkan glsl 中的非统一纹理访问

Question

我正在尝试编写一个计算着色器，它对图像进行光线跟踪，图像 A 的 yz 平面样本右侧的像素，图像 B 左侧的像素。

我不想对两个图像都进行采样，所以我尝试通过以下方式使用非统一访问：

texture(textures[nonuniformEXT(sampler_id)], vec2(0.5));

并在着色器中启用相关扩展。 这会触发以下验证层错误：

Message: Validation Error: [ VUID-VkShaderModuleCreateInfo-pCode-01091 ] Object 0: handle = 0x55a1c21315d0, name = Logical device: AMD RADV RAVEN2, type = VK_OBJECT_TYPE_DEVICE; | MessageID = 0xa7bb8db6 | vkCreateShaderModule(): The SPIR-V Capability (SampledImageArrayNonUniformIndexing) was declared, but none of the requirements were met to use it. The Vulkan spec states: If pCode declares any of the capabilities listed in the SPIR-V Environment appendix, one of the corresponding requirements must be satisfied (https://vulkan.lunarg.com/doc/view/1.2.182.0/linux/1.2-extensions/vkspec.html#VUID-VkShaderModuleCreateInfo-pCode-01091)

如果我阅读文档，这似乎是一项硬件功能，但有人说如果创建正确的扩展 object，我仍然可以进行非统一访问。但我不完全确定该怎么做。

Answer 1

您必须在创建设备时启用该功能。

您可以通过调用vkGetPhysicalDeviceFeatures2并跟随pNext链直到VkPhysicalDeviceVulkan12Features来检查是否支持该功能，并检查shaderSampledImageArrayNonUniformIndexing成员是否为VK_TRUE 。

之后，当使用vkCreateDevice创建设备时，在pCreateInfo结构内，在pNext链中，您必须将VkPhysicalDeviceVulkan12Features的shaderSampledImageArrayNonUniformIndexing设置为VK_TRUE 。

bool checkForNonUniformIndexing(VkPhysicalDevice physicalDevice)
{
    VkPhysicalDeviceFeatures2 features;
    vkGetPhysicalDeviceFeatures2(physicalDevice, &features);

    if(features.sType != VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_FEATURES_2)
    {
        return false;
    }

    const VkPhysicalDeviceFeatures2* next = &features;

    do
    {
        // We know the type of the struct based on the `sType` member, but the first 
        // two fields are the same in all of these structs. There may be a more appropriate 
        // generic structure to use, but as long as we don't access any further members
        // we should be mostly fine.
        next = reinterpret_cast<const VkPhysicalDeviceFeatures*>(next->pNext);
        if(next.sType == VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_VULKAN_1_2_FEATURES)
        {
            const VkPhysicalDeviceVulkan12Features* pVk12Features = reinterpret_cast<const VkPhysicalDeviceVulkan12Features*>(next);
            return next.shaderSampledImageArrayNonUniformIndexing == VK_TRUE;
        }
    } while(next);

    return false;
}

VkDevice* createDevice(VkPhysicalDevice physicalDevice, const VkAllocationCallbacks* pAllocator)
{
    VkPhysicalDeviceVulkan12Features features;
    features.sType = VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_VULKAN_1_2_FEATURES;
    features.shaderSampledImageArrayNonUniformIndexing = VK_TRUE;

    VkDeviceCreateInfo createInfo;
    createInfo.sType = VK_STRUCTURE_TYPE_DEVICE_CREATE_INFO;
    createInfo.pNext = &features;
    // Setting other create data

    VkDevice device;
    vkCreateDevice(physicalDevice, &createInfo, pAllocator, &device);

    // Error checking

    return device;
}