Vulkan SDK之 Swapchain

Swapchain是一系列最终会展示给用户的图像的集合。

/*
* Set up swapchain:
* - Get supported uses for all queues
* - Try to find a queue that supports both graphics and present
* - If no queue supports both, find a present queue and make sure we have a
* graphics queue
* - Get a list of supported formats and use the first one
* - Get surface properties and present modes and use them to create a swap
* chain
* - Create swap chain buffers
* - For each buffer, create a color attachment view and set its layout to
* color attachment
*/

 

 

 

Vulkan and the Windowing System

1、跟其他图形API不同，vulkan 将window相关的操作和图形核心的API隔离；窗口使用对应的扩展，KHR 代表了这是一种Khronos Extension.

VK_USE_PLATFORM_ANDROID_KHR - Android
VK_USE_PLATFORM_WAYLAND_KHR - Wayland
VK_USE_PLATFORM_WIN32_KHR - Microsoft Windows
VK_USE_PLATFORM_XCB_KHR - X Window System, using the XCB library
VK_USE_PLATFORM_XLIB_KHR - X Window System, using the Xlib library

2、VkSurfaceKHR 是对原生平台设备表面或者窗口的一种抽象；

Revisiting Instance and Device Extensions

Instance Extensions

Device Extensions

1、swapchain只是一系列需要展示的图片，具体要将这些图片显示到显示器上，需要硬件进行操作，这个时候需要用到 VK_KHR_SWAPCHAIN_EXTENSION_NAME;

Queue Family and Present

1、vkQueuePresentKHR()  需要找到一个同时指出graphics和present的famaliy;

Device Surface Formats

1、 VkSurfaceFormatKHR  能获取当前显示设备指出的VkFormat;

Surface Capabilities

1、Swapchain的创建需要提供一些额外的信息，可以通过vkGetPhysicalDeviceSurfaceCapabilitiesKHR() 和 vkGetPhysicalDeviceSurfacePresentModesKHR()获取；

2、 minImageCount用来决定当前使用的是双缓冲还是三缓冲区。 双缓冲区一个render,一个present； 三缓冲区一个用来present，其他两个用来render;

Different Queue Families for Graphics and Present

1、如果graphics queue和 present queue family是不同的，需要做一些额外的工作可以让imagine在各个queue之间进行共享；

swapchain_ci.imageSharingMode = VK_SHARING_MODE_EXCLUSIVE;
swapchain_ci.queueFamilyIndexCount = 0;
swapchain_ci.pQueueFamilyIndices = NULL;
uint32_t queueFamilyIndices[2] = {
    (uint32_t)info.graphics_queue_family_index,
    (uint32_t)info.present_queue_family_index};
if (info.graphics_queue_family_index != info.present_queue_family_index) {
    // If the graphics and present queues are from different queue families,
    // we either have to explicitly transfer ownership of images between the
    // queues, or we have to create the swapchain with imageSharingMode
    // as VK_SHARING_MODE_CONCURRENT
    swapchain_ci.imageSharingMode = VK_SHARING_MODE_CONCURRENT;
    swapchain_ci.queueFamilyIndexCount = 2;
    swapchain_ci.pQueueFamilyIndices = queueFamilyIndices;
}

Create Swapchain

1、vkCreateSwapchainKHR 创建了一系列的图像来组成swapchain，但在实际使用的过程中，我们需要告诉GPU当前使用的是哪个image，这个时候就用到如下的接口 vkGetSwapchainImagesKHR;通过这个接口你可以获得
一系列images的handle;

Create Image Views

1、swapchain是一系列的images，但是当我们需要使用这些image的时候，我们就需要为image创建imagin view。 “view”用来告诉vulkan如何使用这些imagin。

2、VkImageViewCreateInfo 用来创建所需的imageview;