【Unity】RenderFeature应用（简单场景扫描效果）

RenderFeature 是一个用于渲染图形的概念，通常在图形引擎或游戏引擎中使用。它是一个模块化的组件，负责处理特定的渲染功能，例如阴影、光照、粒子效果等。

点击地面生成一个不断扩展的圆光效果，用于实现一些画面的特效

实现效果

一、实现方法

1.要求和原理

案例是基于unity urp渲染管线制作，使用了RenderFeature后处理效果。

基本原理一句话，通过相机深度图重建像素的世界空间位置，空间坐标和点击点的坐标进行距离运算画出圆。

2.实现步骤

1）创建UniversalRenderPipelineAsset

​ 在编写RenderFeature前需要创建UniversalRenderPipelineAsset

​ Create→Randering→URPAsset（with Universal Render）

​ 创建后会同时生成UniversalRenderPipelineAsset和UniversalRenderData

​ 动态设置当前UniversalRenderPipelineAsset的方法（也可以手动设置）

   //使用的UniversalRenderPipelineAssetpublic UniversalRenderPipelineAsset UniversalRenderPipelineAsset;void Start(){//分别在Graphics和 Quality里设置成使用的UniversalRenderPipelineAssetGraphicsSettings.renderPipelineAsset = UniversalRenderPipelineAsset;QualitySettings.renderPipeline = UniversalRenderPipelineAsset;}

2）编写RenderFeature

​ 创建RenderFeature，具体介绍可以参见【Unity】RenderFeature笔记

​ Create→Randering→RenderFeature

​ 下面是通用的shader后处理方法，不同的是参数内容和方法

using UnityEngine;
using UnityEngine.Rendering;
using UnityEngine.Rendering.Universal;public class ScanRenderPassFeature : ScriptableRendererFeature
{class CustomRenderPass : ScriptableRenderPass{public Material _Material;public Vector4 _Pos;//点击点public Color _Color;//线颜色public float _Interval;//线间距public float _Strength;//强度范围public override void Execute(ScriptableRenderContext context, ref RenderingData renderingData){// Matrix4x4 frustumCorners = GetFrustumCornersRay();CommandBuffer cmd = CommandBufferPool.Get("ScanRender");_Material.SetVector("_CentorPoint", _Pos);_Material.SetColor("_Color", _Color);_Material.SetFloat("_Interval", _Interval);_Material.SetFloat("_Strength", _Strength);cmd.Blit(colorAttachment, RenderTargetHandle.CameraTarget.Identifier(), _Material);//执行CommandBuffercontext.ExecuteCommandBuffer(cmd);//回收CommandBufferCommandBufferPool.Release(cmd);}}CustomRenderPass m_ScriptablePass;public Shader ScanShader;public Vector4 Pos;public Color Color;public float Interval;//间距public float Strength;//强度/// <inheritdoc/>public override void Create(){m_ScriptablePass = new CustomRenderPass();m_ScriptablePass._Material = new Material(ScanShader);m_ScriptablePass._Pos = Pos;m_ScriptablePass._Color = Color;m_ScriptablePass._Interval = Interval;m_ScriptablePass._Strength = Strength;// Configures where the render pass should be injected.m_ScriptablePass.renderPassEvent = RenderPassEvent.AfterRendering;}public void SetParam(){m_ScriptablePass._Pos = Pos;m_ScriptablePass._Strength = Strength;}public override void AddRenderPasses(ScriptableRenderer renderer, ref RenderingData renderingData){renderer.EnqueuePass(m_ScriptablePass);}
}

3）编写shader

​ shader要实现的是两个功能，一是深度图重建像素的世界空间位置，再是根据空间位置画出扩展圆

​ 重建像素的世界空间位置可以参照官方的案例

​ 从深度纹理重建像素的世界空间位置 |URP |7.7.1 (unity3d.com)

​ 核心方法：

​ ComputeWorldSpacePosition：是一个用于计算物体在世界空间中位置的函数。它通常用于计算游戏中的物体 在世界坐标系中的位置。

​ SampleSceneDepth：用于获取深度图像。它主要用于实现一些基本的深度相关功能，比如观察场景中物体深 度信息、计算物体之间的距离等。

​ 下面结合官方的方法进行修改

Shader "Unlit/ScanShaderURP"
{Properties{_CentorPoint("CentrePoint",Vector) = (0, 0, 0, 0)_Color("color",Color) = (1,1,1,1)   //颜色}SubShader{Tags { "RenderType"="Opaque" }LOD 100Pass{HLSLPROGRAM#pragma vertex vert#pragma fragment frag#include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/DeclareDepthTexture.hlsl"struct Attributes{float4 positionOS   : POSITION;};struct Varyings{float4 positionHCS  : SV_POSITION;};float4x4 _FrustumCornersRay;float  _Interval;//间距float _Strength;//强度sampler2D _CameraColorTexture;float4 _CentorPoint;float4 _Color;Varyings vert(Attributes IN){Varyings OUT;OUT.positionHCS = TransformObjectToHClip(IN.positionOS.xyz);return OUT;}half4 frag(Varyings IN) : SV_Target{//uv变换float2x2 muls = float2x2(-1, 0, 0, 1);float2 centerUV = float2(1, 0);float2 UV =1-( mul(( IN.positionHCS.xy / _ScaledScreenParams.xy), muls)+centerUV);//获取深度图
#if UNITY_REVERSED_Zreal depth = SampleSceneDepth(UV);
#elsereal depth = lerp(UNITY_NEAR_CLIP_VALUE, 1, SampleSceneDepth(UV));
#endif//获取世界坐标位置float3 worldPos = ComputeWorldSpacePosition(UV, depth, UNITY_MATRIX_I_VP);half4 col2 = tex2D(_CameraColorTexture, UV);float lerpValue = 0;//对截面外的空间进行屏蔽if (depth < _ProjectionParams.z - 1) {float Mul = distance(_CentorPoint.xyz, worldPos.xyz);//change控制圈的距离float change = _Strength;//Mul的值是一定大于0的//第一个smoothstep小于change的值裁剪为0，大于_Interval + change的为1//第二个smoothstep大于_Interval + change的为1，小于的为0//两smoothstep相减得到0 + change和 _Interval + change距离间0到1的变化，其余为0float lerp1 = smoothstep(0 + change, _Interval + change, Mul);float lerp2 = smoothstep(_Interval + change, _Interval + change, Mul);float dis = lerp1 - lerp2;lerpValue = dis;}half4 myCol = lerp(col2, _Color, lerpValue);return myCol;}ENDHLSL}}
}

4）控制方法

using System.Linq;
using UnityEngine;
using UnityEngine.Rendering.Universal;public class ScanControl : MonoBehaviour
{public UniversalRendererData renderData;ScanRenderPassFeature custom;private void Start(){custom = renderData.rendererFeatures.OfType<ScanRenderPassFeature>().FirstOrDefault();}private void Update(){if (Input.GetMouseButtonDown(1)){Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);RaycastHit hit;if (Physics.Raycast(ray, out hit)){Vector3 vector = hit.point;Vector4 vector4 = new Vector4(vector.x, vector.y, vector.z, 1);custom.Pos = vector4;custom.Strength = 0;}}}private void LateUpdate(){custom.Strength += Time.deltaTime*10;custom.SetParam();}
}

3.在built-in里的实现方法

shader

Shader "Unlit/ScanShaderBuiltIn"
{Properties{_MainTex("Base (RGB)", 2D) = "white" {} // 主纹理_CentorPoint("CentrePoint",Vector) = (0, 0, 0, 0)_Color("color",Color) = (1,1,1,1)   //颜色，一般用fixed4_InverseZ("InverseZ", Float) = -1 }SubShader{Tags { "RenderType"="Opaque" }LOD 100Pass{CGPROGRAM#pragma vertex vert#pragma fragment frag#include "UnityCG.cginc"struct appdata{float4 vertex : POSITION;float2 uv : TEXCOORD0;};struct v2f{float2 uv : TEXCOORD0;float4 pos : SV_POSITION;float3 viewVec :TEXCOORD1;};sampler2D _MainTex; // 主纹理float _Interval;//间距float _Strength;//强度float _InverseZ;sampler2D _CameraColorTexture;sampler2D _CameraDepthTexture;float4 _CentorPoint;fixed4 _Color;v2f vert (appdata v){v2f o;o.uv = v.uv;o.pos = UnityObjectToClipPos(v.vertex); //MVP变换float4 screenPos = ComputeScreenPos(o.pos); // 计算“齐次空间”下的屏幕坐标// float4 ndcPos = (screenPos / screenPos.w) * 2 - 1; //屏幕坐标--->ndc坐标变换公式// float4 ndcPos = o.pos / o.pos.w; //手动进行透视除法float3 ndcPos = float3(o.uv.xy * 2.0 - 1.0, 1); //直接把uv映射到ndc坐标float far = _ProjectionParams.z; //获取投影信息的z值，代表远平面距离float3 clipVec = float3(ndcPos.x, ndcPos.y, ndcPos.z * _InverseZ) * far; //裁切空间下的视锥顶点坐标o.viewVec = mul(unity_CameraInvProjection, clipVec.xyzz).xyz; //观察空间下的视锥向量return o;}fixed4 frag (v2f i) : SV_Target{fixed4 col2 = tex2D(_MainTex, i.uv);//   fixed4 col2 = tex2D(_CameraColorTexture, i.uv);float depth = SAMPLE_DEPTH_TEXTURE(_CameraDepthTexture,i.uv);//采样深度图depth = Linear01Depth(depth); //转换为线性深度float3 viewPos = i.viewVec * depth; //获取实际的观察空间坐标（插值后）float3  worldPos = mul(unity_CameraToWorld, float4(viewPos,1)).xyz; //观察空间-->世界空间坐标float factor = 0;if (depth < _ProjectionParams.z - 1) {float Mul = distance(_CentorPoint.xyz, worldPos.xyz);float change = _Strength;//Mul的值是一定大于0的//第一个smoothstep小于change的值裁剪为0，大于_Interval + change的为1//第二个smoothstep大于_Interval + change的为1，小于的为0//两smoothstep相减得到0 + change和 _Interval + change距离间0到1的变化，其余为0float lerp1 = smoothstep(0 + change, _Interval + change, Mul);float lerp2 = smoothstep(_Interval + change, _Interval + change, Mul);float dis = lerp1 - lerp2;float lerpDis = smoothstep(0.99, 1, dis);factor = dis;}fixed4 myCol = lerp(col2, _Color, factor);return myCol;}ENDCG}}
}

控制脚本

using System.Collections;
using System.Collections.Generic;
using UnityEngine;public class ScanManager : MonoBehaviour
{[SerializeField]private bool enableWave = false; // 是否开启扫描特效[SerializeField]private Shader scanShader;private Material material = null; // 材质Vector4 _Pos=Vector4.zero;public Color _Color;float _Interval=1;//间距float _Strength=0;//强度// Start is called before the first frame updatevoid Start(){material = new Material(scanShader);}// Update is called once per framevoid Update(){if (Input.GetMouseButtonDown(1)){Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);RaycastHit hit;if (Physics.Raycast(ray, out hit)){Vector3 vector = hit.point;Vector4 vector4 = new Vector4(vector.x, vector.y, vector.z, 1);Debug.Log(vector4);_Pos = vector4;_Strength = 0;enableWave = true;}}}private void OnRenderImage(RenderTexture src, RenderTexture dest){if (enableWave){_Strength += Time.deltaTime * 10;material.SetVector("_CentorPoint", _Pos);material.SetColor("_Color", _Color);material.SetFloat("_Interval", _Interval);material.SetFloat("_Strength", _Strength);Graphics.Blit(src, dest, material);}else{Graphics.Blit(src, dest);}}}