# 2. 图形绘制流水的基本原理和实践 (1)

#### Vulkan 初始化

如果考虑复杂的 Vulkan 使用场景 一般只需要一个 Vulkan 实例，逻辑设备可以有多个

![image.png](https://image-1253155090.cos.ap-nanjing.myqcloud.com/202306011100314.png)

Layer 类似于函数重载 ![image.png](https://image-1253155090.cos.ap-nanjing.myqcloud.com/202306011109825.png)

Vulkan 队列 ![image.png](https://image-1253155090.cos.ap-nanjing.myqcloud.com/202306011113713.png)

创建 Swapchain 属于 Vulkan 的一个拓展 ![image.png](https://image-1253155090.cos.ap-nanjing.myqcloud.com/202306011115457.png)

#### 渲染主循环

顶点缓存的优化是，可以把经常要变化的坐标和法线放在一个 Buffer，而 UV 和其他属性放一个 Buffer

![image.png](https://image-1253155090.cos.ap-nanjing.myqcloud.com/202306011135916.png)

索引缓存避免跳转过大，造成 Cache miss ![image.png](https://image-1253155090.cos.ap-nanjing.myqcloud.com/202306011138268.png)

Draw ，Draw Index 绘制，Draw Indirect 是间接绘制，不需要知道顶点的数量，不用绑定顶点数据，是通过 Buffer 里的数据实时生成顶点。

![image.png](https://image-1253155090.cos.ap-nanjing.myqcloud.com/202306011139967.png)

Vulkan 的 NDC 坐标

深度的算法是 revert z，z 越大深度越小，存在深度图里的值越小。当 z 为 0 时，深度图里存 1。 ![image.png](https://image-1253155090.cos.ap-nanjing.myqcloud.com/202306011142208.png)

View port 绘制区域一般和纹理区域是一致的， 想要一张图里画多张图的时候，要设置 Viewport 到对应绘制区域，比如 CSM

![image.png](https://image-1253155090.cos.ap-nanjing.myqcloud.com/202306011344246.png)

裁剪选项

![image.png](https://image-1253155090.cos.ap-nanjing.myqcloud.com/202306011346135.png)

浮点数精度，位置需要 32 位，颜色 8 位就够了

![image.png](https://image-1253155090.cos.ap-nanjing.myqcloud.com/202306011350359.png)

片段输出

当在 Frag 里不做深度修改的时候，可以在片段之前就做深度剔除。 但这是 PC 端常用的方式，移动端的 Tile-base 没法知道深度是否会修改，所以这方法没有用？

![image.png](https://image-1253155090.cos.ap-nanjing.myqcloud.com/202306011351517.png)

RenderPass 内 Vulkan 的绑定流程 ![image.png](https://image-1253155090.cos.ap-nanjing.myqcloud.com/202306011354732.png)

深度纹理最终 pass 是不需要写入操作的，最终 Pass 只提供读取就行。 一个 Command Buffer 里的所有指令是同步的

![image.png](https://image-1253155090.cos.ap-nanjing.myqcloud.com/202306011410391.png)

### 参考资料

* Vulkan 参考资料
  * 《Vulkan应用开发指南》
  * [Brief guide to Vulkan layers (renderdoc.org)](https://renderdoc.org/vulkan-layer-guide.html)
  * [Vulkan in 30 minutes (renderdoc.org)](https://renderdoc.org/vulkan-in-30-minutes.html)
  * [vulkan11-reference-guide.pdf (khronos.org)](https://www.khronos.org/files/vulkan11-reference-guide.pdf)
  * [Vulkan® 1.3.246 - A Specification (khronos.org)](https://registry.khronos.org/vulkan/specs/1.3/html/)
  * [Vulkan 教程|极客教程 (geek-docs.com)](https://geek-docs.com/vulkan/vulkan-tutorial/vulkan-tutorial-index.html)
* Vulkan示例代码
  * [GitHub - SaschaWillems/Vulkan: Examples and demos for the new Vulkan API](https://github.com/SaschaWillems/Vulkan)
  * [GitHub - KhronosGroup/Vulkan-Samples: One stop solution for all Vulkan samples](https://github.com/KhronosGroup/Vulkan-Samples)
  * [GitHub - google/filament: Filament is a real-time physically based rendering engine for Android, iOS, Windows, Linux, macOS, and WebGL2](https://github.com/google/filament)
* Vulkan调试工具
  * RenderDoc
  * Nvidia Nsight Tool
  * AMD Radeon GPU Profiler • Qualcomm Snapdragon Profiler • Arm Mobile Studio


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