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前言

在上一篇文章中，我们实现了能量罩外发光的效果。但是，这样看我们的能量罩十分单调不好看。在这篇文章中，我们给能量罩加上花纹、扭曲流光，使其变好看。

• Unity中URP下实现能量罩（外发光）

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一、能量罩花纹

1、在属性面板接收能量罩花纹纹理

_MainTex(“MainTex”,2D) = “white”{}

2、申明 纹理 和 采样器

TEXTURE2D(_MainTex);SAMPLER(sampler_MainTex);float4 _MainTex_ST;

3、在顶点着色器，应用 Tilling 和 Offset

o.uv.zw = TRANSFORM_TEX(v.uv,_MainTex);

4、在片元着色器，纹理采样后，与之前的结果相乘输出

float4 mainTex = SAMPLE_TEXTURE2D(_MainTex,sampler_MainTex,i.uv.zw);
col *= mainTex;

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二、能量罩流光

1、在顶点着色器，记录原uv值

o.uv.xy = v.uv;

2、在片元着色器，使用 uv 的 y 值，乘以一个系数 加上_Time.y实现流动的效果

col *= frac(i.uv.y * _Flow + _Time.y);

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三、抓屏扭曲

1、在URP设置中，开启抓屏

2、申明 抓屏纹理 和 采样器

TEXTURE2D(_CameraOpaqueTexture);SAMPLER(sampler_CameraOpaqueTexture);

3、在片元着色器

• 对花纹纹理，进行 y 方向上的流动采样，得到扰动纹理

float4 distortTex = SAMPLE_TEXTURE2D(_MainTex,sampler_MainTex,i.uv.zw + float2(0,_Time.x));

• 线性差值得到 扰动采样UV

float2 distortUV = lerp(uv,distortTex.rr,_Distort);

• 对抓屏纹理进行纹理采样

half4 opaqueTex = SAMPLE_TEXTURE2D(_CameraOpaqueTexture,sampler_CameraOpaqueTexture,distortUV);

• 与之前的输出结果，相乘输出

half4 distort = opaqueTex;
col *= distort;
return col;

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四、测试代码

//流光扭曲花纹
Shader "MyShader/URP/P4_3_7"
{
    Properties 
    {
        [Header(MainTex)]
        _MainTex("MainTex",2D) = "white"{}
        [Header(HighLight)]
        _HighLightColor("HighLightColor",Color) = (0,0,0,0)
        _HighLightFade("HighLight",Float) = 1.0
        [Header(Fresnel)]
        _FresnelIntensity("FresnelIntensity",Range(1,15)) = 1.0
        _FresnelColor("FresnelColor",Color) = (0,0,0,0)
        [Header(Flow)]
        _Flow("Flow",Float)=0
        _Distort("Distort",Range(0,1)) = 0.3
    }
    SubShader
    {
        Tags
        {
            //告诉引擎，该Shader只用于 URP 渲染管线
            "RenderPipeline"="UniversalPipeline"
            //渲染类型
            "RenderType"="Transparent"
            //渲染队列
            "Queue"="Transparent"
        }
        
        Pass
        {
            Blend One One
            ZWrite Off
            Name "Unlit"
          
            HLSLPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            // Pragmas
            #pragma target 2.0
            
            // Includes
            #include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Color.hlsl"
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Input.hlsl"

            CBUFFER_START(UnityPerMaterial)
            half4 _HighLightColor;
            half _HighLightFade;
            half _FresnelIntensity;
            half4 _FresnelColor;
            half _Flow;
            half _Distort;
            CBUFFER_END

            TEXTURE2D(_MainTex);SAMPLER(sampler_MainTex);float4 _MainTex_ST;
            TEXTURE2D(_CameraDepthTexture);SAMPLER(sampler_CameraDepthTexture);
            TEXTURE2D(_CameraOpaqueTexture);SAMPLER(sampler_CameraOpaqueTexture);
            //struct appdata
            //顶点着色器的输入
            struct Attributes
            {
                float3 positionOS : POSITION;
                float2 uv : TEXCOORD0;
                half3 normalOS : NORMAL;
            };
            //struct v2f
            //片元着色器的输入
            struct Varyings
            {
                float4 positionCS : SV_POSITION;
                float4 uv : TEXCOORD0;
                float4 screenPos : TEXCOORD1;
                float3 positionWS : TEXCOORD2;
                float3 positionVS : TEXCOORD3;
                half3 normalWS : TEXCOORD4;
                
            };
            //v2f vert(Attributes v)
            //顶点着色器
            Varyings vert(Attributes v)
            {
                Varyings o = (Varyings)0;
                o.positionWS = TransformObjectToWorld(v.positionOS);
                o.positionVS = TransformWorldToView(o.positionWS);
                o.positionCS = TransformWViewToHClip(o.positionVS);
                o.screenPos = ComputeScreenPos(o.positionCS);
                o.normalWS = TransformObjectToWorldNormal(v.normalOS);
                o.uv.xy = v.uv;
                o.uv.zw = TRANSFORM_TEX(v.uv,_MainTex);
                return o;
            }
            //fixed4 frag(v2f i) : SV_TARGET
            //片元着色器
            half4 frag(Varyings i) : SV_TARGET
            {
                half4 col=0;
                //深度图
                //float2 uv = i.screenPos.xy / i.screenPos.w;
                float2 uv = i.positionCS.xy/ _ScreenParams.xy;
                float4 cameraDepthTex = SAMPLE_TEXTURE2D(_CameraDepthTexture,sampler_CameraDepthTexture,uv);
                float depthTex = LinearEyeDepth(cameraDepthTex.r,_ZBufferParams);
                float depth = depthTex + i.positionVS.z;
                float4 highLight = 1 - depth;
                highLight = pow(saturate(highLight),_HighLightFade);
                highLight *= _HighLightColor;
                col += saturate(highLight);

                //fresnel外发光
                //pow(max(0,dot(N,V)),Intensity)
                half3 N = normalize(i.normalWS);
                half3 V = normalize(_WorldSpaceCameraPos - i.positionWS);
                half NdotV = dot(N,V);
                half4 fresnel = pow(max(0,1 - NdotV),_FresnelIntensity);
                fresnel *= _FresnelColor;
                col += fresnel;
                //能量罩花纹
                float4 mainTex = SAMPLE_TEXTURE2D(_MainTex,sampler_MainTex,i.uv.zw);
                col += mainTex * 0.15;
                
                //流光
                half flowMask = frac(i.uv.y * _Flow + _Time.y);
                col *= flowMask;
                
                //抓屏流光扭曲
                float4 distortTex = SAMPLE_TEXTURE2D(_MainTex,sampler_MainTex,i.uv.zw + float2(0,_Time.x));
                float2 distortUV = lerp(uv,distortTex.rr,_Distort);
                half4 opaqueTex = SAMPLE_TEXTURE2D(_CameraOpaqueTexture,sampler_CameraOpaqueTexture,distortUV);

                half4 distort = opaqueTex;

                col *= distort;
                return col;
            }
            ENDHLSL
        }
    }
}