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
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GRD更像是Gpu driven管线下的SRP Batches升级，RenderGraph相较于HDRP之前使用的版本换了一套API。
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：
- 说明这是一个外部置入的RenderTexture
- 红色方块说明存在写入操作
- 绿色方块指存在读取操作（红绿方块说明读写操作）
- 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同时保留了旧的Feature逻辑与RenderGraph逻辑(打开任意pass文件为例)：
public classDistortTunnelPass_Tunnel : ScriptableRenderPass
{classPassData
{publicRenderer tunnelObject;publicMaterial 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}#pragma warning disable 618, 672 //Type or member is obsolete, Member overrides obsolete member //Unity calls the Configure method in the Compatibility mode (non-RenderGraph path) public override voidConfigure(CommandBuffer cmd, RenderTextureDescriptor cameraTextureDescripor)
{
}//Unity calls the Execute method in the Compatibility mode public override void Execute(ScriptableRenderContext context, refRenderingData 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 voidRecordRenderGraph(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= newMaterialPropertyBlock();
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。
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并没有整理旧API的代码和相关工具类，
以至于容易使用旧的API导致报错，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：
usingUnityEngine;usingUnityEngine.Rendering.Universal;usingUnityEngine.Rendering;public classMyBlurSceneController : MonoBehaviour
{publicMaterial material;
[Range(2, 15)] public int blurPasses = 3;
[Range(0, 4)] public int downSample = 0;
[Range(0.0f, 10f)] public float offset = 0.2f;public RenderPassEvent injectionPoint =RenderPassEvent.BeforeRenderingPostProcessing;public int injectionPointOffset = 0;public ScriptableRenderPassInput inputRequirements =ScriptableRenderPassInput.Color;public CameraType cameraType =CameraType.Game;privateMyBlurPass mMyBlurPass;private voidOnEnable()
{
SetupPass();
RenderPipelineManager.beginCameraRendering+=OnBeginCamera;
}private voidOnDisable()
{
RenderPipelineManager.beginCameraRendering-=OnBeginCamera;
}public virtual voidSetupPass()
{
mMyBlurPass= newMyBlurPass();
mMyBlurPass.renderPassEvent= injectionPoint +injectionPointOffset;
mMyBlurPass.material=material;
mMyBlurPass.ConfigureInput(inputRequirements);
}public virtual voidOnBeginCamera(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：
usingUnityEngine;usingUnityEngine.Rendering.RenderGraphModule;usingUnityEngine.Rendering;usingUnityEngine.Rendering.Universal;usingUnityEngine.Rendering.RenderGraphModule.Util;public classMyBlurPass : ScriptableRenderPass
{public classPassData
{publicTextureHandle tempRt1;publicTextureHandle tempRt2;
}publicMaterial 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 voidRecordRenderGraph(RenderGraph renderGraph, ContextContainer frameData)
{var resourceData = frameData.Get<UniversalResourceData>();var passData = newPassData();var w = Screen.width >>downSample;var h = Screen.height >>downSample;
RenderTextureDescriptor textureProperties= new RenderTextureDescriptor(w, h, RenderTextureFormat.Default, 0);
passData.tempRt1= UniversalRenderer.CreateRenderGraphTexture(renderGraph, textureProperties, "MyBlurPassTempRt1", false);
textureProperties= new RenderTextureDescriptor(w, h, RenderTextureFormat.Default, 0);
passData.tempRt2= UniversalRenderer.CreateRenderGraphTexture(renderGraph, textureProperties, "MyBlurPassTempRt2", false);var rt1 =passData.tempRt1;var rt2 =passData.tempRt2;//将屏幕RT Blit到rt1上 var para = new RenderGraphUtils.BlitMaterialParameters(resourceData.activeColorTexture, rt1, material, 0);
renderGraph.AddBlitPass(para,"MyBlurPassBlitFirst");
material.SetFloat("_SampleOffset", offset);//模糊迭代 for (int i = 0; i < blurPasses - 1; ++i)
{
para= new RenderGraphUtils.BlitMaterialParameters(rt1, rt2, material, 0);
renderGraph.AddBlitPass(para, $"MyBlurPassBlit_{i}");var tmp =rt1;
rt1=rt2;
rt2=tmp;
}//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_))
{
builder.UseTexture(rt1);
builder.SetRenderAttachment(resourceData.activeColorTexture,0);
builder.SetRenderFunc<PassData>((data, context) =>{
MaterialPropertyBlock materialPropertyBlock= newMaterialPropertyBlock();
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);
});
}
}
}
接着在ShaderGraph中连出模糊的逻辑，注意Blit对应的参数_BlitTexture、_BlitScaleBias：
最后在场景中挂载控制器以及材质球，即可使用该模糊Pass。
