vkCreateCommandPool

函数原型

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：

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：

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

// 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!");
	}
}