在 URP 中的兼容性模式下编写可编程渲染通道

注意：Unity 不再开发或改进不使用Render Graph API 的渲染路径。在开发新的图形功能时，请改用 Render Graph API。要使用此页面上的说明，请在 URP 图形设置（项目设置 (Project Settings) > 图形 (Graphics)）中启用兼容性模式（禁用 Render Graph）(Compatibility Mode (Render Graph Disabled))。

以下示例是执行以下步骤的 ScriptableRenderPass 实例：

1. 使用 RenderTextureDescriptor API 创建临时渲染纹理。
2. 使用 RTHandle 和 Blit API 将自定义着色器的两个通道应用于摄像机输出。

编写可编程渲染通道后，可使用以下方法之一注入渲染通道：

• 使用 RenderPipelineManager API
• 使用可编程渲染器功能

创建可编程渲染通道

本节演示如何创建可编程渲染通道。

1. 创建一段新的 C# 脚本并将其命名为 RedTintRenderPass.cs。

2. 在脚本中，删除 Unity 在 RedTintRenderPass 类中插入的代码。添加以下 using 指令：

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

3. 创建继承自 ScriptableRenderPass 类的 RedTintRenderPass 类。

   public class RedTintRenderPass : ScriptableRenderPass
   

4. 将 Execute 方法添加到类中。Unity 每帧调用此方法，每个摄像机调用一次。此方法可用于实现可编程渲染通道的渲染逻辑。

   public override void Execute(ScriptableRenderContext context, ref RenderingData renderingData)
   { }
   

以下是本节中 RedTintRenderPass.cs 文件的完整代码。

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

public class RedTintRenderPass : ScriptableRenderPass
{
    public override void Execute(ScriptableRenderContext context,
        ref RenderingData renderingData)
    {
        
    }
}

实现自定义渲染通道的设置

1. 为材质添加一个字段以及使用该字段的构造函数。

   private Material material;
   
   public RedTintRenderPass(Material material)
   {
       this.material = material;
   }
   

2. 添加 RenderTextureDescriptor 字段并在构造函数中将其初始化：

   using UnityEngine;
   
   private RenderTextureDescriptor textureDescriptor;
   
   public RedTintRenderPass(Material material)
   {
       this.material = material;
   
       textureDescriptor = new RenderTextureDescriptor(Screen.width,
           Screen.height, RenderTextureFormat.Default, 0);
   }
   

3. 声明 RTHandle 字段以存储对临时红色色调纹理的引用。

   private RTHandle textureHandle;
   

4. 实现 Configure 方法。Unity 在执行渲染通道之前调用此方法。

   public override void Configure(CommandBuffer cmd,
       RenderTextureDescriptor cameraTextureDescriptor)
   {
       //Set the red tint texture size to be the same as the camera target size.
       textureDescriptor.width = cameraTextureDescriptor.width;
       textureDescriptor.height = cameraTextureDescriptor.height;
   
       //Check if the descriptor has changed, and reallocate the RTHandle if necessary.
       RenderingUtils.ReAllocateIfNeeded(ref textureHandle, textureDescriptor);
   }
   

5. 使用__ Blit__“位块传输 (Bit Block Transfer)”的简写。blit 操作是将数据块从内存中的一个位置传输到另一个位置的过程。
   See in Glossary 方法可将自定义着色器中的两个渲染通道应用于摄像机输出。

   public override void Execute(ScriptableRenderContext context,
       ref RenderingData renderingData)
   {
       //Get a CommandBuffer from pool.
       CommandBuffer cmd = CommandBufferPool.Get();
   
       RTHandle cameraTargetHandle =
           renderingData.cameraData.renderer.cameraColorTargetHandle;
   
       // Blit from the camera target to the temporary render texture,
       // using the first shader pass.
       Blit(cmd, cameraTargetHandle, textureHandle, material, 0);
       // Blit from the temporary render texture to the camera target,
       // using the second shader pass.
       Blit(cmd, textureHandle, cameraTargetHandle, material, 1);
   
       //Execute the command buffer and release it back to the pool.
       context.ExecuteCommandBuffer(cmd);
       CommandBufferPool.Release(cmd);
   }
   

6. 实现在渲染通道执行后销毁材质和临时渲染纹理的 Dispose 方法。

   public void Dispose()
   {
       #if UNITY_EDITOR
               if (EditorApplication.isPlaying)
               {
                   Object.Destroy(material);
               }
               else
               {
                   Object.DestroyImmediate(material);
               }
       #else
               Object.Destroy(material);
       #endif
           
       if (textureHandle != null) textureHandle.Release();
   }
   

自定义渲染通道代码

以下是自定义渲染通道脚本的完整代码。

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

public class RedTintRenderPass : ScriptableRenderPass
{
    private Material material;

    private RenderTextureDescriptor textureDescriptor;
    private RTHandle textureHandle;

    public RedTintRenderPass(Material material)
    {
        this.material = material;

        textureDescriptor = new RenderTextureDescriptor(Screen.width,
            Screen.height, RenderTextureFormat.Default, 0);
    }

    public override void Configure(CommandBuffer cmd,
        RenderTextureDescriptor cameraTextureDescriptor)
    {
        // Set the texture size to be the same as the camera target size.
        textureDescriptor.width = cameraTextureDescriptor.width;
        textureDescriptor.height = cameraTextureDescriptor.height;

        // Check if the descriptor has changed, and reallocate the RTHandle if necessary
        RenderingUtils.ReAllocateIfNeeded(ref textureHandle, textureDescriptor);
    }

    public override void Execute(ScriptableRenderContext context,
        ref RenderingData renderingData)
    {
        //Get a CommandBuffer from pool.
        CommandBuffer cmd = CommandBufferPool.Get();

        RTHandle cameraTargetHandle =
            renderingData.cameraData.renderer.cameraColorTargetHandle;

        // Blit from the camera target to the temporary render texture,
        // using the first shader pass.
        Blit(cmd, cameraTargetHandle, textureHandle, material, 0);
        // Blit from the temporary render texture to the camera target,
        // using the second shader pass.
        Blit(cmd, textureHandle, cameraTargetHandle, material, 1);

        //Execute the command buffer and release it back to the pool.
        context.ExecuteCommandBuffer(cmd);
        CommandBufferPool.Release(cmd);
    }

    public void Dispose()
    {
    #if UNITY_EDITOR
        if (EditorApplication.isPlaying)
        {
            Object.Destroy(material);
        }
        else
        {
            Object.DestroyImmediate(material);
        }
    #else
            Object.Destroy(material);
    #endif

        if (textureHandle != null) textureHandle.Release();
    }
}

红色色调效果的自定义着色器

本节包含用于实现红色色调效果的自定义着色器的代码。

Shader "CustomEffects/RedTint"
{
    HLSLINCLUDE
    
        #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"

    
        float4 RedTint (Varyings input) : SV_Target
        {
            float3 color = SAMPLE_TEXTURE2D(_BlitTexture, sampler_LinearClamp, input.texcoord).rgb;
            return float4(1, color.gb, 1);
        }

        float4 SimpleBlit (Varyings input) : SV_Target
        {
            float3 color = SAMPLE_TEXTURE2D(_BlitTexture, sampler_LinearClamp, input.texcoord).rgb;
            return float4(color.rgb, 1);
        }
    
    ENDHLSL
    
    SubShader
    {
        Tags { "RenderType"="Opaque" "RenderPipeline" = "UniversalPipeline"}
        LOD 100
        ZTest Always ZWrite Off Cull Off
        Pass
        {
            Name "RedTint"

            HLSLPROGRAM
            
            #pragma vertex Vert
            #pragma fragment RedTint
            
            ENDHLSL
        }
        
        Pass
        {
            Name "SimpleBlit"

            HLSLPROGRAM
            
            #pragma vertex Vert
            #pragma fragment SimpleBlit
            
            ENDHLSL
        }
    }
}