Unity6 URP17使用初探

1.简介

随着Unity6的发布，URP17也已经可以上手使用，相对旧的版本改动较大的是加入了

新的RenderGraph、STP、Foveated rendering、GPU Resident Drawer等功能，部分功能只需要开关参数即可使用，

而GPU Resident Drawer好比BRG（BatchRendererGroup）的升级，RenderGraph相较HDRP那一版也有诸多差异。

最大的不同是，使用URP17编写Feature时，必须依赖于RenderGraph进行编写，接下来就来介绍一下。

 

1.1 相关Demo

目前URP17比较容易找到的学习Demo如下：

• URP17 Package内自带的Samples
• Fantasy Kingdom (https://assetstore.unity.com/packages/essentials/tutorial-projects/fantasy-kingdom-in-unity-6-urp-298128)
• 在Unity Hub可以直接下载的Universal 3D sample（包含3个场景）

2.RenderGraph

打开任意URP的示例场景查看，RenderGraphView上各图标含义如下：

1. 说明这是一个外部置入的RenderTexture
2. 红色方块说明存在写入操作
3. 绿色方块指存在读取操作（红绿方块说明读写操作）
4. 该图标说明标记了全局RenderTexture

 而顶部表明当前渲染一帧的各个Pass，左侧是各类RT。

 

URP17的一些案例同时保留了旧的Feature逻辑与RenderGraph逻辑(打开任意pass文件为例)：

public class DistortTunnelPass_Tunnel : ScriptableRenderPass
{
    class PassData
    {
        public Renderer tunnelObject;
        public Material tunnelMaterial;
    }


#pragma warning disable 618, 672 // Type or member is obsolete, Member overrides obsolete member

    // Unity calls the Configure method in the Compatibility mode (non-RenderGraph path)
    public override void Configure(CommandBuffer cmd, RenderTextureDescriptor cameraTextureDescripor)
    {
    }

    // Unity calls the Execute method in the Compatibility mode
    public override void Execute(ScriptableRenderContext context, ref RenderingData renderingData)
    {
    }

#pragma warning restore 618, 672

    // Unity calls the RecordRenderGraph method to add and configure one or more render passes in the render graph system.
    public override void RecordRenderGraph(RenderGraph renderGraph, ContextContainer frameData)
    {
    }
}

参考时忽略掉Configure和Execute的逻辑，执行逻辑关注RecordRenderGraph函数。

 

2.1 操作方式的改变

在RenderGraph中，之前的RTHandle由于不在该系统中托管，进入RenderGraph的材质都需要调用API进行转换，

转换为RendeGraph的RT后，无需考虑释放操作：

RenderTextureDescriptor textureProperties = new RenderTextureDescriptor(Screen.width, Screen.height, RenderTextureFormat.Default, 0);
TextureHandle textureHandle = UniversalRenderer.CreateRenderGraphTexture(renderGraph, textureProperties, "My texture", false);

相关文档：

https://docs.unity3d.com/Manual/urp/render-graph-create-a-texture.html

 

此外RenderGraph对于空调用的pass，也会剔除进行优化，使用者需要手动标记以防止被剔除。

 

2.1 RecordRenderGraph

在该函数内可组织渲染逻辑，pass相关的逻辑需放在对应的代码块中，例如：

using (var builder = renderGraph.AddRasterRenderPass<PassData>(passName, out _))
{
    builder.UseTexture(rt1);
    builder.SetRenderAttachment(resourceData.activeColorTexture, 0);

    builder.SetRenderFunc<PassData>((data, context) =>
    {
        MaterialPropertyBlock materialPropertyBlock = new MaterialPropertyBlock();
        materialPropertyBlock.SetTexture("_BlitTexture", rt1);
        materialPropertyBlock.SetVector("_BlitScaleBias", new Vector4(1, 1, 0, 0));

        context.cmd.DrawProcedural(Matrix4x4.identity, material, 0, MeshTopology.Triangles, 3, 1, materialPropertyBlock);
    });
}

URP提供了多种RenderPass，例如处理光栅化相关逻辑使用RasterRenderPass组织相关逻辑，

涉及到调用旧API的逻辑，可以使用UnsafePass(https://docs.unity3d.com/6000.0/Documentation/Manual/urp/render-graph-unsafe-pass.html)

在RenderPass的代码块中可使用builder对象配置RenderTarget、标记材质的读写等

而具体的pass绘制逻辑则在SetRenderFunc代码块中。

 

RecordRenderGraph内可以调用多次AddRenderPass，但URP并没有对API进行整理，

以至于不小心混用了API就会报错，这点需要注意。

 

3.编写Feature

3.1 Blit与SetTarget

从前有句俗话“切RT的性能消耗相当于半个pass”，Unity SRP在几个版本的升级都在逐渐强调不切RenderTarget直接绘制，

如Cockpit Demo的屏幕空间描边。

 

3.2 屏幕模糊Demo

下面通过屏幕模糊Demo案例，演示URP17下pass的编写。

 

通过外部EnqueuePass的方式，在场景中通过控制器脚本添加该Pass，

MyBlurSceneController.cs：

using UnityEngine;
using UnityEngine.Rendering.Universal;
using UnityEngine.Rendering;

public class MyBlurSceneController : MonoBehaviour
{
    public Material material;
    [Range(2, 15)] public int blurPasses = 3;
    [Range(0, 4)] public int downSample = 0;
    [Range(0.0f, 10f)] public float offset = 0.02f;

    public RenderPassEvent injectionPoint = RenderPassEvent.BeforeRenderingPostProcessing;
    public int injectionPointOffset = 0;
    public ScriptableRenderPassInput inputRequirements = ScriptableRenderPassInput.Color;
    public CameraType cameraType = CameraType.Game;

    private MyBlurPass mMyBlurPass;


    private void OnEnable()
    {
        SetupPass();

        RenderPipelineManager.beginCameraRendering += OnBeginCamera;
    }

    private void OnDisable()
    {
        RenderPipelineManager.beginCameraRendering -= OnBeginCamera;
    }

    public virtual void SetupPass()
    {
        mMyBlurPass = new MyBlurPass();

        mMyBlurPass.renderPassEvent = injectionPoint + injectionPointOffset;
        mMyBlurPass.material = material;

        mMyBlurPass.ConfigureInput(inputRequirements);
    }

    public virtual void OnBeginCamera(ScriptableRenderContext ctx, Camera cam)
    {
        if (mMyBlurPass == null || material == null)
            return;

        if ((cam.cameraType & cameraType) == 0) return;

        mMyBlurPass.blurPasses = blurPasses;
        mMyBlurPass.downSample = downSample;
        mMyBlurPass.offset = offset;

        cam.GetUniversalAdditionalCameraData().scriptableRenderer.EnqueuePass(mMyBlurPass);
    }
}

 

MyBlurPass.cs：

using System;

using UnityEngine;
using UnityEngine.Rendering.RenderGraphModule;
using UnityEngine.Rendering;
using UnityEngine.Rendering.Universal;

public class MyBlurPass : ScriptableRenderPass
{
    private class PassData
    {
        public TextureHandle target;
        public TextureHandle source;

        public TextureHandle finalDrawTexture;

        public int blurPasses;

        public Material material;
    }

    public Material material;
    [Range(2, 15)] public int blurPasses = 3;
    [Range(1, 4)] public int downSample = 1;
    [Range(0.0f, 10f)] public float offset = 0.2f;


    public override void RecordRenderGraph(RenderGraph renderGraph, ContextContainer frameData)
    {
        var resourceData = frameData.Get<UniversalResourceData>();

        var w = Screen.width >> downSample;
        var h = Screen.height >> downSample;

        RenderTextureDescriptor textureProperties = new RenderTextureDescriptor(w, h, RenderTextureFormat.Default, 0);
        var rt1 = UniversalRenderer.CreateRenderGraphTexture(renderGraph, textureProperties, "MyBlurPassTempRt1", false);

        textureProperties = new RenderTextureDescriptor(w, h, RenderTextureFormat.Default, 0);
        var rt2 = UniversalRenderer.CreateRenderGraphTexture(renderGraph, textureProperties, "MyBlurPassTempRt2", false);

        //URP17还有一个接口renderGraph.AddBlitPass，但不能外部传PassData，因此目前版本只能用UnsafePass调用旧的Blit API来写

        using (var builder = renderGraph.AddUnsafePass("Blur Pass Begin", out PassData passData, profilingSampler))
        {
            passData.source = resourceData.activeColorTexture;
            passData.target = rt1;
            passData.material = material;

            builder.UseTexture(resourceData.activeColorTexture);
            builder.UseTexture(rt1, AccessFlags.Write);
            builder.SetRenderFunc((PassData data, UnsafeGraphContext context) => ExecuteUnsafeBlitPass(data, context));
        }

        material.SetFloat("_SampleOffset", offset);

        using (var builder = renderGraph.AddUnsafePass("Blur Pass Iterate", out PassData passData, profilingSampler))
        {
            passData.source = rt1;
            passData.target = rt2;
            passData.material = material;
            passData.blurPasses = blurPasses;

            builder.UseTexture(rt1, AccessFlags.ReadWrite);
            builder.UseTexture(rt2, AccessFlags.ReadWrite);
            builder.SetRenderFunc((PassData data, UnsafeGraphContext context) => ExecuteUnsafeBlitPassIterate(data, context));
        }

        //通过直接绘制的方式，将模糊RT绘制到屏幕上
        using (var builder = renderGraph.AddRasterRenderPass<PassData>(passName, out PassData passData))
        {
            passData.finalDrawTexture = rt1;

            builder.UseTexture(passData.finalDrawTexture);
            builder.SetRenderAttachment(resourceData.activeColorTexture, 0);

            builder.SetRenderFunc<PassData>((passData, context) =>
            {
                MaterialPropertyBlock materialPropertyBlock = new MaterialPropertyBlock();
                materialPropertyBlock.SetTexture("_BlitTexture", passData.finalDrawTexture);
                materialPropertyBlock.SetVector("_BlitScaleBias", new Vector4(1, 1, 0, 0));

                context.cmd.DrawProcedural(Matrix4x4.identity, material, 0, MeshTopology.Triangles, 3, 1, materialPropertyBlock);
            });
        }
    }

    private static void ExecuteUnsafeBlitPass(PassData passData, UnsafeGraphContext context)
    {
        CommandBuffer unsafeCmd = CommandBufferHelpers.GetNativeCommandBuffer(context.cmd);

        TextureHandle source = passData.source;
        TextureHandle target = passData.target;

        Blitter.BlitCameraTexture(unsafeCmd, source, target, RenderBufferLoadAction.DontCare, RenderBufferStoreAction.Store, passData.material, 0);
    }

    private static void ExecuteUnsafeBlitPassIterate(PassData passData, UnsafeGraphContext context)
    {
        CommandBuffer unsafeCmd = CommandBufferHelpers.GetNativeCommandBuffer(context.cmd);

        TextureHandle source = passData.source;
        TextureHandle target = passData.target;

        Blitter.BlitCameraTexture(unsafeCmd, source, target, RenderBufferLoadAction.DontCare, RenderBufferStoreAction.Store, passData.material, 0);

        for (int i = 0; i < passData.blurPasses; ++i)
        {
            Blitter.BlitCameraTexture(unsafeCmd, source, target, RenderBufferLoadAction.DontCare, RenderBufferStoreAction.Store, passData.material, 0);
            Blitter.BlitCameraTexture(unsafeCmd, target, source, RenderBufferLoadAction.DontCare, RenderBufferStoreAction.Store, passData.material, 0);
        }
    }
}

 

 

接着在ShaderGraph中组合出模糊逻辑，注意Blit对应的参数_BlitTexture、_BlitScaleBias，采样贴图在SG中对应SAMPLE_TEXTURE2D：

 

 

最后在场景中挂载控制器以及材质球，即可使用该模糊Pass。