前言

这节课非常干！！

建议可以先过一遍，然后了解更多urp管线知识后再来回顾。

up非常细心过了很多知识点。

由于水平有限，现阶段先简单归类下这节课讲了哪些大内容，后续回顾下。

课程地址：https://www.bilibili.com/video/BV13F411e7Ai
PPT地址：https://docs.qq.com/slide/DUUxtdE5GcEtwZmNm
项目地址：https://github.com/Thousandyearsofwar/CommandBufferDemo

没有太多参考内容的笔记（可折叠展开）

从自定义RenderPipeline分析ScriptableRenderContext与CommandBuffer

详细回顾下课程

重点在于以下四个测试

1. CullingResults+DrawingSettings+FilteringSettings
2. Override RenderStateBlock
3. RenderType Match Subshader
4. TagName+TagVlaues Match Subshader or Pass

相关代码：here

大致是使用ScriptableRenderPass做一些有意思的事情，如修改匹配物体的材质和深度模板测试规则等等

这里提供其他参考资料：

• 放牛的星星大佬翻译catlikecoding相关文章：https://zhuanlan.zhihu.com/p/333275514
• Scriptable Render Pipeline：https://www.cnblogs.com/leixinyue/p/11038565.html
• 猫都能看懂的URP RenderFeature使用及自定义方法:https://zhuanlan.zhihu.com/p/396965255
• 猫都能看懂的CommandBuffer在URP中的使用方法:https://zhuanlan.zhihu.com/p/400977346

command buffer插入时机

主要讲了新的urp和builtin有很大不同，导致原有的插入时机基本都不生效了

RenderTexture Test

完整代码：RenderTextureRequestPass

Test0 : new RenderTexture(cameraDescriptor)

void RTRequestTest0_0(CommandBuffer commandBuffer, ref RenderingData renderingData)
{
    RenderTextureDescriptor cameraDescriptor = renderingData.cameraData.cameraTargetDescriptor;
    //1.renderTexture == null必要性 只创建一张RenderTexture
    //2.IsCreated 防止未被创建
    //3.CoreUtils.Destroy 安全Destory RenderTexture
    //4.编辑器上面的bug 
    //从哪里参考:ShadowsMidtonesHighlightsEditor.cs
    //5.renderTexture.Create();
    if (renderTexture == null || !renderTexture.IsCreated())
    {
        CoreUtils.Destroy(renderTexture);
        renderTexture = new RenderTexture(cameraDescriptor);
        renderTexture.name = "RequestRT";
    }
    //配置RenderTarget[渲染目标]
    ConfigureTarget(renderTexture);
}

这个函数是在OnCameraSetup里面调用的，所以增加了很多判空处理，

为什么不能在Pass生成的时候创建：
渲染纹理的像素内容可能会在某些事件中丢失，比如：加载新关卡，屏幕进入保护模式，全屏进出，当这种情况发生时，你的RenderTexture将再次变成“尚未创建”，遇到这种情况需要用IsCreate函数进行检测。与其他“原生引擎对象”的类型一样，需要关注RenderTexture的生命周期，并在使用完成之后使用Release函数进行释放，因为Render不会像普通托管类型那样被GC。

Test1:RenderTexture.GetTemporary(cameraDescriptor)

void RTRequestTest0_1(CommandBuffer commandBuffer, ref RenderingData renderingData)
{
    RenderTextureDescriptor cameraDescriptor = renderingData.cameraData.cameraTargetDescriptor;
    //1.申请临时的RenderTexture 必须手动Release掉
    //需要时刻关心生命周期！！
    //2.释放资源的区别:RenderTexture.Release和Destroy。https://zhuanlan.zhihu.com/p/41251356 
    //RenderTexture.Release释放显存，内存不释放
    //Destroy会把Object销毁的同时连带显存释放掉
    //所以出于性能考虑，频繁使用Destory会加重申请内存的负担
    //从哪里参考:ShadowUtils.cs
    renderTexture = RenderTexture.GetTemporary(cameraDescriptor);
    renderTexture.name = "RequestRT";
    ConfigureTarget(renderTexture);
}

Test2:Shader.PropertyToID

MRT shader: here

pass中：

renderTextureID = Shader.PropertyToID("Request_ID");

shader中：

TEXTURE2D(Request_ID);	SAMPLER(sampler_Request_ID);

void RTRequestTest0_2(CommandBuffer commandBuffer, ref RenderingData renderingData)
{
  RenderTextureDescriptor cameraDescriptor = renderingData.cameraData.cameraTargetDescriptor;
  //1.Shader.PropertyToID的作用：
  //用字符串获取一个唯一的HashID
  //相当于一个全局的id，需要保证其他Material着色使用这张RenderTexture时，这张RenderTexture渲染完成，没有被Release掉
  //就不用手动setTexture了
  renderTextureID = Shader.PropertyToID("Request_ID");
  //2.RenderTexture.GetTemporary和commandBuffer.GetTemporaryRT[申请RenderTexture的区别]
  //1.RenderTexture.GetTemporary需要手动释放掉
  //2.使用CommandBuffer申请的临时的RenderTexture如果都没有显式地使用(Release)TemporaryRT，在相机完成渲染后或Graphics.ExecuteCommandBuffer完成后被移除(Remove)(Destory?)
  commandBuffer.GetTemporaryRT(renderTextureID, cameraDescriptor, FilterMode.Bilinear);

  ConfigureTarget(renderTextureID);
}

Test3:renderTargetHandle

//使用URP的renderTargetHandle获取PropertyToID
void RTRequestTest0_3(CommandBuffer commandBuffer, ref RenderingData renderingData)
{
  RenderTextureDescriptor cameraDescriptor = renderingData.cameraData.cameraTargetDescriptor;

  renderTargetHandle.Init("Request_Handle");
  //commandBuffer.GetTemporaryRT(renderTargetHandle.Identifier(), cameraDescriptor, FilterMode.Bilinear);//错误示范
  commandBuffer.GetTemporaryRT(renderTargetHandle.id, cameraDescriptor, FilterMode.Bilinear);

  ConfigureTarget(renderTargetHandle.Identifier());
}

RenderTargetHandle

using UnityEngine.Scripting.APIUpdating;

namespace UnityEngine.Rendering.Universal
{
    // RenderTargetHandle can be thought of as a kind of ShaderProperty string hash
    [MovedFrom("UnityEngine.Rendering.LWRP")] public struct RenderTargetHandle
    {
        public int id { set; get; }
        private RenderTargetIdentifier rtid { set; get; }

        public static readonly RenderTargetHandle CameraTarget = new RenderTargetHandle {id = -1 };

        public RenderTargetHandle(RenderTargetIdentifier renderTargetIdentifier)
        {
            id = -2;
            rtid = renderTargetIdentifier;
        }

			//...

        public void Init(string shaderProperty)
        {
            // Shader.PropertyToID returns what is internally referred to as a "ShaderLab::FastPropertyName".
            // It is a value coming from an internal global std::map<char*,int> that converts shader property strings into unique integer handles (that are faster to work with).
            id = Shader.PropertyToID(shaderProperty);
        }

        public void Init(RenderTargetIdentifier renderTargetIdentifier)
        {
            id = -2;
            rtid = renderTargetIdentifier;
        }

        public RenderTargetIdentifier Identifier()
        {
            if (id == -1)
            {
                return BuiltinRenderTextureType.CameraTarget;
            }
            if (id == -2)
            {
                return rtid;
            }
            return new RenderTargetIdentifier(id);
        }

				//...
    }
}

[Wrong]Test4:commandBuffer.SetRenderTarget(renderTextureID)

//错误对比用放置于Excute中
void RTRequestTest0_4(CommandBuffer commandBuffer, ScriptableRenderContext context, ref RenderingData renderingData)
{
  RenderTextureDescriptor cameraDescriptor = renderingData.cameraData.cameraTargetDescriptor;

  renderTextureID = Shader.PropertyToID("Request_ID");
  commandBuffer.GetTemporaryRT(renderTextureID, cameraDescriptor, FilterMode.Bilinear);
  // commandBuffer.GetTemporaryRT(renderTextureID, cameraDescriptor.width, cameraDescriptor.height, 16, FilterMode.Bilinear,
  // UnityEngine.Experimental.Rendering.GraphicsFormat.A2B10G10R10_UNormPack32, 1, false, RenderTextureMemoryless.None, false);//Full of parameters version

  commandBuffer.SetRenderTarget(renderTextureID);

  context.ExecuteCommandBuffer(commandBuffer);
  commandBuffer.Clear();
}

public override void Execute(ScriptableRenderContext context, ref RenderingData renderingData)
{
  CommandBuffer commandBuffer = CommandBufferPool.Get();

  RTRequestTest0_4(commandBuffer, context, ref renderingData);

  //Do something at here...
  using (new ProfilingScope(commandBuffer, m_ProfilingSampler))
  {
    commandBuffer.ClearRenderTarget(true, true, Color.blue, 1);
  }
  context.ExecuteCommandBuffer(commandBuffer);
  commandBuffer.Clear();
  CommandBufferPool.Release(commandBuffer);
}

会导致：skybox绘制到了错误的render target。

问题在于：
有些pass没有自动切回RenderTarget
部分pass缺少configure()重写的函数，比如DrawSkyboxPass

最好是使用ConfigureTarget，除非你自己知道在干嘛。

//in ScriptableRenderPass class
public virtual void Configure(CommandBuffer cmd, RenderTextureDescriptor cameraTextureDescriptor)
{}

Draw Mesh Test

介绍了几个绘制网格的api，重点在gpu instancing部分，详见课程和参考链接

command buffer常用函数

非常干，建议结合官方api文档使用，最好是能配合案例

URP下渲染流程和ScriptableRenderFeature以及ScriptableRenderPass的原理

看着源码讲解了几个重要的类

• ScriptableRenderFeature
• ScriptableRenderPass
• ScriptableRenderer
• ForwardRenderer

梳理了urp运行的流程，建议看完catlikecoding文章再来阅读

自定义后处理使用

• VolumeManager的使用
• 材质尽量使用MaterialPropertyBlock避免创建额外实例

command buffer注意事项

作业

结合学过的知识，复刻传送门效果

大体可以拆分为以下：

• 门的出现动画，可以用dotween做，这里直接配合timeline简单k了个动画
• 边框描边，借鉴了shader graph中的Rectangle节点

// 使用mask来插值门颜色和边框颜色
float2 d = abs(uv * 2 - 1) - float2(width, height);
d = 1 - d / fwidth(d);
mask = saturate(min(d.x, d.y));

• 门背后遮挡物体，这里用的模板测试，优点是实现简单（可以直接用renderfeature），但对视角有要求。本来想用alphatest去做，但考虑到需要修改人物shader，就没继续了。
• 毛玻璃效果，对当前画面（不包括门）抓屏后再用任意模糊算法模糊，重新采样即可。
• 物体与门交互，采样屏幕深度图与门的深度比较即可，参考卡通水那节

课程参考资料

• Unity官方文档

• SRP概念相关:

  • https://www.cnblogs.com/leixinyue/p/11038565.html
  • https://en.wikipedia.org/wiki/Render_Target
  • https://zhuanlan.zhihu.com/p/363793724

• LoadAction/StoreAction RendertexuteMemeoryLess

  • https://answer.uwa4d.com/question/5e856425acb49302349a1119
  • https://zhuanlan.zhihu.com/p/262537295
  • https://developer.apple.com/library/archive/documentation/3DDrawing/Conceptual/MTLBestPracticesGuide/LoadandStoreActions.html

• Instances:

  • https://www.xuanyusong.com/archives/4504
  • https://www.xuanyusong.com/archives/4640
  • https://www.xuanyusong.com/archives/4683
  • https://www.cnblogs.com/OneStargazer/p/15170931.html

• Draw相关指令:

  • https://github.com/keijiro/Swarm
  • https://github.com/keijiro/GraphPlotter

• Compute Shader:

  • https://cheneyshen.com/directcompute-tutorial-for-unity-kernels-and-thread-groups/
  • https://catlikecoding.com/unity/tutorials/basics/compute-shaders/

• MSAA:

  • https://www.zhihu.com/question/479915187
  • https://github.com/wlgys8/SRPLearn/wiki/MSAA_Implement

• RT精度:

  • https://en.wikipedia.org/wiki/Colour_banding

补充参考文章

• Hacking into Unity’s rendering pipelines：https://www.youtube.com/watch?v=xrmbtBHJXt8&t=388s
• https://docs.unity.cn/cn/current/Manual/GraphicsCommandBuffers.html
• Using Entity Command Buffers - Unite Copenhagen：https://www.youtube.com/watch?v=SecJibpoTYw&t=34s
• 放牛的星星大佬翻译catlikecoding相关文章：https://zhuanlan.zhihu.com/p/333275514
• 猫都能看懂的URP RenderFeature使用及自定义方法:https://zhuanlan.zhihu.com/p/396965255
• 猫都能看懂的CommandBuffer在URP中的使用方法:https://zhuanlan.zhihu.com/p/400977346
• 大佬笔记：
  • https://www.yuque.com/6527chen/ldyt32/pate7b#AwCUH
  • https://www.yuque.com/sugelameiyoudi-jadcc/okgm7e/fanvuu
  • https://zhuanlan.zhihu.com/p/488968981
  • https://zhuanlan.zhihu.com/p/510965477