Vulkan学习笔记：CommandBuffer

// count：生成几个commandbuffer，level：多线程渲染时使用
void xGenCommandBuffer(VkCommandBuffer* commandbuffer, int count, VkCommandBufferLevel level /* = VK_COMMAND_BUFFER_LEVEL_PRIMARY*/)
{
	VkCommandBufferAllocateInfo cbai = {};
	cbai.sType = VK_STRUCTURE_TYPE_COMMAND_BUFFER_ALLOCATE_INFO;
	cbai.level = level;
	cbai.commandPool = GetCommandPool();
	cbai.commandBufferCount = count;
	vkAllocateCommandBuffers(GetVulkanDevice(), &cbai, commandbuffer);
}

void xBeginOneTimeCommandBuffer(VkCommandBuffer* commandbuffer)
{
	// 生成一个commandbuffer
	xGenCommandBuffer(commandbuffer, 1);
	VkCommandBufferBeginInfo cbbi = {};
	cbbi.sType = VK_STRUCTURE_TYPE_COMMAND_BUFFER_BEGIN_INFO;
	// 这个flag设定使得commandbuffer是一个onetime
	cbbi.flags = VK_COMMAND_BUFFER_USAGE_ONE_TIME_SUBMIT_BIT;
	// 开始设置commandbuffer
	vkBeginCommandBuffer(*commandbuffer, &cbbi);
}

void xEndOneTimeCommandBuffer(VkCommandBuffer& commandbuffer)
{
	// commandbuffer设置完毕，等待发送到GPU
	vkEndCommandBuffer(commandbuffer);
	// 等待commandbuffer完成
	xWaitForCommmandFinish(commandbuffer);
	// 销毁commandbuffer
	vkFreeCommandBuffers(GetVulkanDevice(), GetCommandPool(), 1, &commandbuffer);
}

// 发送commandbuffer，等待完成
void xWaitForCommmandFinish(VkCommandBuffer commandbuffer)
{
	// commandbuffer提交信息，或者说是如何打开
	VkSubmitInfo submitinfo = {};
	submitinfo.sType = VK_STRUCTURE_TYPE_SUBMIT_INFO;
	submitinfo.commandBufferCount = 1;
	submitinfo.pCommandBuffers = &commandbuffer;
	// fence是一种同步的方式，它在整个命令管线里做一个标记，当GPU执行到了这个标记后，fence变成已被执行了的状态，
	// 也意味着fence前面的commandbuffer中的指令也全部已经被执行完成了。
	VkFence fence;
	VkFenceCreateInfo fenceinfo = {};
	fenceinfo.sType = VK_STRUCTURE_TYPE_FENCE_CREATE_INFO;
	// 创建一个标记
	vkCreateFence(GetVulkanDevice(), &fenceinfo, nullptr, &fence);
	// 提交commandbuffer或者信号量到GPU
	// args:提交路线，VkSubmitInfo结构体数量，VkSubmitInfo实例，fence
	vkQueueSubmit(GetGraphicQueue(), 1, &submitinfo, fence);
	// 等待commandbuffer执行完成：waitAll参数true是等待所有的fence执行完，false是等待的fence任一一个完成就执行后面的代码
	// 从参数看，一个wait可以等待多个fence
	vkWaitForFences(GetVulkanDevice(), 1, &fence, VK_TRUE, 1000000);
	vkDestroyFence(GetVulkanDevice(), fence, nullptr);
}