首页 计算机图形学 Unity URP

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# 综述

常常听说 URP 里最多只能执行一个 Pass，但这其实是不对的，为啥呢？
就是因为 RenderFeature，URP 把实际上 Pass 执行的顺序抽象到了 CommandList 中了，即可以手动的在 C# 端控制 Pass 的执行顺序，而不需要硬写在代码里了。
并且一个 RenderFeature 里可以执行哪些 Pass 也都是自己决定的
接下来以毛玻璃后处理效果来记录 RenderFeature 用法

# RenderPass

URP14.0 后必须在 Pass 的 CameraSetup 阶段中获取 cameraColorTargetHandle , 禁止在 Feature 中获取

而且必须用 RTHandle 代替 RTTargetHandle

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var renderer = renderingData.cameraData.renderer;
//获取屏幕的RT和材质,传递到Pass中  
RenderTargetIdentifier currentRT = renderer.cameraColorTargetHandle;
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using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Rendering;
using UnityEngine.Rendering.Universal;

public class SFXDistortedPass : ScriptableRenderPass
{
    //接收Feature脚本传入的数据
    private RenderTargetIdentifier sourceRT;
    private Material material;

    private static string m_RTName = "SFXDistorted";

    private static int rtTagId = Shader.PropertyToID(m_RTName);
    //临时RT
    private RTHandle tempRT = RTHandles.Alloc(rtTagId,name : m_RTName);

    public void Setup(Material mat)
    {
        this.material = mat;
    }

    public override void Execute(ScriptableRenderContext context, ref RenderingData data)
    {
        CommandBuffer cmd = CommandBufferPool.Get("SFXDistorted22");

        //向cmd中写入所有的渲染命令
        Render(cmd, ref data);
        //执行命令
        context.ExecuteCommandBuffer(cmd);
        //执行完毕后释放该命令
        CommandBufferPool.Release(cmd);
    }

    void Render(CommandBuffer cmd, ref RenderingData data)
    {
        //创建一个临时的RenderTexture,参数和相机的一致
        RenderTextureDescriptor opaqueDesc = data.cameraData.cameraTargetDescriptor;
        opaqueDesc.depthBufferBits = 0;
        cmd.GetTemporaryRT(rtTagId,opaqueDesc);

        //将源RY通过Material写入到tempRT
        cmd.Blit(sourceRT,rtTagId,material);

        //再从tempRT写回到sourceRT
        cmd.Blit(rtTagId,sourceRT);
    }

    public override void OnCameraSetup(CommandBuffer cmd, ref RenderingData renderingData)
    {
        base.OnCameraSetup(cmd,ref renderingData);
        var renderer = renderingData.cameraData.renderer;
        //获取屏幕的RT和材质,传递到Pass中  
        RenderTargetIdentifier currentRT = renderer.cameraColorTargetHandle;
        sourceRT = currentRT;
    }

    public override void OnCameraCleanup(CommandBuffer cmd)
    {
        base.OnCameraCleanup(cmd);
        tempRT.Release();
    }
}

# RenderFeature

实际的 Pass 执行都放到 context 的 EnqueuePass 中去了

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using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Rendering;
using UnityEngine.Rendering.Universal;

public class SFXDistortedFeature : ScriptableRendererFeature
{
    [Serializable]
    public class DistortedSetting
    {
        public RenderPassEvent Event = RenderPassEvent.AfterRenderingOpaques;
        public Shader shader;
        [Tooltip("扭曲强度")]
        public float distortedInt;
        [Tooltip("扭曲图")]
        public Texture2D distortedTex;
    }

    public DistortedSetting _settings = new DistortedSetting();
    private Material matInstance;
    private SFXDistortedPass pass;
    private static readonly int distortedInt = Shader.PropertyToID("_distortedInt");
    private static readonly int distortedTex = Shader.PropertyToID("_distortedTex");

    public override void Create()
    {
        pass = new SFXDistortedPass();
        pass.renderPassEvent = _settings.Event;
    }

    public override void AddRenderPasses(ScriptableRenderer renderer, ref RenderingData data)
    {
        //检查Shader是否为空,为空则创建一个默认的  
        if (_settings.shader == null) return;
        if (matInstance == null)
        {
            matInstance = CoreUtils.CreateEngineMaterial(_settings.shader);
        }
        matInstance.SetTexture(distortedTex,_settings.distortedTex);
        matInstance.SetFloat(distortedInt,_settings.distortedInt);
        pass.Setup(matInstance);
        //Pass进入队列
        renderer.EnqueuePass(pass);
    }
}

# 设置

# Shader

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Shader "URP/distortedPM"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
        _BaseColor("Test Color",Color) = (1,1,1,1)
    }
    SubShader
    {
        Pass
        {
            Cull Off
            ZTest Always
            ZWrite Off
            HLSLPROGRAM

            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
            #include "Packages/com.unity.render-pipelines.core/ShaderLibrary/SpaceTransforms.hlsl"

            #pragma vertex Vertex
            #pragma fragment fragment

            Texture2D _MainTex,_distortedTex;
            SamplerState sampler_MainText,sampler_distortedTex;
            TEXTURE2D(_CameraColorTexture);
            SAMPLER(sampler_CameraColorTexture);
            half4 _BaseColor;
            half _distortedInt;

            struct a2v
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
            };
            struct v2f{
                float4 pos: SV_POSITION;
                float2 uv: TEXCOORD0;
            };

            v2f Vertex(a2v v)
            {
                v2f o;
                o.pos = TransformObjectToHClip(v.vertex);
                o.uv = v.uv;
                return o;
            }

            half4 fragment(v2f i): SV_TARGET{
                half distortedTex = _distortedTex.Sample(sampler_distortedTex, i.uv);
                //half4 col = _MainTex.Sample(sampler_MainTex, lerp(i.uv,distortedTex,_distortedInt));
                float2 uv = distortedTex*_distortedInt  + i.uv;
                return SAMPLE_TEXTURE2D(_CameraColorTexture, sampler_CameraColorTexture, uv);
            }

            ENDHLSL
        }
    }
}