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vkCreateCommandPool

函数原型

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VkResult vkCreateCommandPool(
    VkDevice                                    device,
    const VkCommandPoolCreateInfo*              pCreateInfo,
    const VkAllocationCallbacks*                pAllocator,
    VkCommandPool*                              pCommandPool);

描述

创建命令缓冲池。

参数

  • device : 用于创建命令缓冲池的逻辑设备。
  • pCreateInfo : VkCommandPoolCreateInfo 结构体指针，包含创建命令缓冲池的信息。
  • pAllocator : host memory 分配器。
  • pCommandPool : 创建返回的命令缓冲池句柄。

补充

VkCommandPoolCreateInfo 结构体定义： 

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typedef struct VkCommandPoolCreateInfo {
    VkStructureType             sType;
    const void*                 pNext;
    VkCommandPoolCreateFlags    flags;               //设置命令缓冲的分配行为
    uint32_t                    queueFamilyIndex;    //队列族索引
} VkCommandPoolCreateInfo;

VkCommandPoolCreateFlags 枚举定义： 

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typedef enum VkCommandPoolCreateFlagBits {
    VK_COMMAND_POOL_CREATE_TRANSIENT_BIT = 0x00000001,             //在较短时间内会重复重置或释放
    VK_COMMAND_POOL_CREATE_RESET_COMMAND_BUFFER_BIT = 0x00000002,  //命令缓冲允许使用vkResetCommandBuffer或vkBeginCommandBuffer进行重置，否则不允许使用
    VK_COMMAND_POOL_CREATE_PROTECTED_BIT = 0x00000004,                //受保护的命令缓冲
} VkCommandPoolCreateFlagBits;

返回值

  • VK_SUCCESS : 成功创建命令缓冲池。
  • 其他 : 创建失败。

代码示例

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// 查询设备的可用队列族，-1代表无效
struct  QueueFamilyIndices {
    // 支持图像绘制的队列
    uint32_t graphicsFamily = -1;

    // 支持图形呈现的队列
    uint32_t presentFamily = -1;

    bool isComplete() {
        return (graphicsFamily >= 0) && (presentFamily >= 0);
    }
};

// 查询可用的图形队列和呈现队列
QueueFamilyIndices findQueueFamilies(VkPhysicalDevice device) {
    QueueFamilyIndices indices;

    uint32_t queueFamilyCount = 0;
    vkGetPhysicalDeviceQueueFamilyProperties(device, &queueFamilyCount, nullptr);
    vector<VkQueueFamilyProperties> queueFamilies(queueFamilyCount);
    vkGetPhysicalDeviceQueueFamilyProperties(device, &queueFamilyCount, queueFamilies.data());

    int index = 0;
    for (const auto& queueFamily : queueFamilies) {
        if (queueFamily.queueFlags & VK_QUEUE_GRAPHICS_BIT) { // 目前，我们只要寻找图形队列即可
            indices.graphicsFamily = index;
        }

        VkBool32 presentSupport = false;
        vkGetPhysicalDeviceSurfaceSupportKHR(device, index, surface, &presentSupport);
        if (presentSupport) {
            indices.presentFamily = index;
        }

        if (indices.isComplete()) {
            break;
        }
        index++;
    }

    return indices;
}

// 创建指令池
void createCommandPool() {
    QueueFamilyIndices queueFamilyIndices = findQueueFamilies(physicalDevice);

    VkCommandPoolCreateInfo poolInfo{};
    poolInfo.sType = VK_STRUCTURE_TYPE_COMMAND_POOL_CREATE_INFO;
    poolInfo.queueFamilyIndex = queueFamilyIndices.graphicsFamily;

    if (vkCreateCommandPool(device, &poolInfo, nullptr, &commandPool) != VK_SUCCESS) {
        throw std::runtime_error("Failed to create command pool!");
    }
}