【从UnityURP开始探索游戏渲染】专栏-直达

自定义渲染通道是一种改变通用渲染管道（URP）如何渲染场景或场景中的对象的方法。自定义呈现通道(RenderPass)包含自己的Render代码，可以在注入点将其添加到RenderPass中。

添加自定义呈现通道(RenderPass)：

使用Scriptable render pass API创建自定义render pass的代码。
将自定的render pass注入到URP管线中的指定注入点中，有两种方式：
- 用RenderPipelineManager API注入自定义渲染通道
- 或者通过创建一个可脚本化的RendererFeature添加到URP渲染器中。

使用Scriptable render pass API创建自定义render pass

Example custom render pass

using UnityEngine;
using UnityEngine.Rendering;
using UnityEngine.Rendering.Universal;internal class ColorBlitPass : ScriptableRenderPass
{ProfilingSampler m_ProfilingSampler = new ProfilingSampler("ColorBlit");Material m_Material;RTHandle m_CameraColorTarget;float m_Intensity;public ColorBlitPass(Material material){m_Material = material;renderPassEvent = RenderPassEvent.BeforeRenderingPostProcessing;}public void SetTarget(RTHandle colorHandle, float intensity){m_CameraColorTarget = colorHandle;m_Intensity = intensity;}public override void OnCameraSetup(CommandBuffer cmd, ref RenderingData renderingData){ConfigureTarget(m_CameraColorTarget);}public override void Execute(ScriptableRenderContext context, ref RenderingData renderingData){var cameraData = renderingData.cameraData;if (cameraData.camera.cameraType != CameraType.Game)return;if (m_Material == null)return;CommandBuffer cmd = CommandBufferPool.Get();using (new ProfilingScope(cmd, m_ProfilingSampler)){m_Material.SetFloat("_Intensity", m_Intensity);Blitter.BlitCameraTexture(cmd, m_CameraColorTarget, m_CameraColorTarget, m_Material, 0);}context.ExecuteCommandBuffer(cmd);cmd.Clear();CommandBufferPool.Release(cmd);}
}

将自定的render pass注入到URP管线中的指定注入点中

用RenderPipelineManager API注入自定义渲染通道

通过RenderPipelineManager的注入点委托提供执行时机，加上Camera的EnqueuePass方法注入自定义RenderPass。

public class EnqueuePass : MonoBehaviour
{[SerializeField] private BlurSettings settings;    private BlurRenderPass blurRenderPass;private void OnEnable(){...blurRenderPass = new BlurRenderPass(settings);// Subscribe the OnBeginCamera method to the beginCameraRendering event.RenderPipelineManager.beginCameraRendering += OnBeginCamera;}private void OnDisable(){RenderPipelineManager.beginCameraRendering -= OnBeginCamera;blurRenderPass.Dispose();...}private void OnBeginCamera(ScriptableRenderContext context, Camera cam){...// Use the EnqueuePass method to inject a custom render passcam.GetUniversalAdditionalCameraData().scriptableRenderer.EnqueuePass(blurRenderPass);}
}

创建一个可脚本化的RendererFeature

此示例执行将屏幕染成绿色的全屏blit。

要创建自定义渲染通道，创建一个名为ColorBlitPass.cs的新c#脚本，然后从示例自定义渲染通道部分粘贴代码。
- 注意：这个例子使用了Blitter API。不要使用CommandBuffer。URP中的Blit API。更多信息请参考Blit。
- 使用上面定义好的定制Render Pass

要创建Scriptable RendererFeature，将自定义渲染通道添加到渲染循环中，请创建一个名为ColorBlitRendererFeature.cs的新c#脚本，然后将示例Scriptable RendererFeature部分中的代码粘贴进来。

Example Scriptable Renderer Feature Scriptable Renderer Feature 添加 render pass 到渲染循环.

using UnityEngine;
using UnityEngine.Rendering;
using UnityEngine.Rendering.Universal;internal class ColorBlitRendererFeature : ScriptableRendererFeature
{public Shader m_Shader;public float m_Intensity;Material m_Material;ColorBlitPass m_RenderPass = null;public override void AddRenderPasses(ScriptableRenderer renderer,ref RenderingData renderingData){if (renderingData.cameraData.cameraType == CameraType.Game)renderer.EnqueuePass(m_RenderPass);}public override void SetupRenderPasses(ScriptableRenderer renderer,in RenderingData renderingData){if (renderingData.cameraData.cameraType == CameraType.Game){// Calling ConfigureInput with the ScriptableRenderPassInput.Color argument// ensures that the opaque texture is available to the Render Pass.m_RenderPass.ConfigureInput(ScriptableRenderPassInput.Color);m_RenderPass.SetTarget(renderer.cameraColorTargetHandle, m_Intensity);}}public override void Create(){m_Material = CoreUtils.CreateEngineMaterial(m_Shader);m_RenderPass = new ColorBlitPass(m_Material);}protected override void Dispose(bool disposing){CoreUtils.Destroy(m_Material);}
}

要创建将像素染成绿色的着色器代码，请创建一个着色器文件，然后从示例着色器部分粘贴代码。

Example shader

着色器执行渲染的GPU端。它从相机中采样颜色纹理，然后输出绿色值设置为所选强度的颜色。
注意：与Blitter API一起使用的着色器必须是手工编码的着色器。图形着色器与Blitter API不兼容。

Shader "ColorBlit"
{SubShader{Tags { "RenderType"="Opaque" "RenderPipeline" = "UniversalPipeline"}LOD 100ZWrite Off Cull OffPass{Name "ColorBlitPass"HLSLPROGRAM#include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"// The Blit.hlsl file provides the vertex shader (Vert),// the input structure (Attributes) and the output structure (Varyings)#include "Packages/com.unity.render-pipelines.core/Runtime/Utilities/Blit.hlsl"#pragma vertex Vert#pragma fragment frag// Set the color texture from the camera as the input textureTEXTURE2D_X(_CameraOpaqueTexture);SAMPLER(sampler_CameraOpaqueTexture);// Set up an intensity parameterfloat _Intensity;half4 frag (Varyings input) : SV_Target{UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX(input);// Sample the color from the input texturefloat4 color = SAMPLE_TEXTURE2D_X(_CameraOpaqueTexture, sampler_CameraOpaqueTexture, input.texcoord);// Output the color from the texture, with the green value set to the chosen intensityreturn color * float4(0, _Intensity, 0, 1);}ENDHLSL}}
}