效果：

shader

Shader "UI/Unlit/Flowlight"
{
    Properties
    {
        [PerRendererData] _MainTex("Sprite Texture", 2D) = "white" {}
         _Color("Tint", Color) = (1, 1, 1, 1)
        [MaterialToggle] PixelSnap("Pixel snap", float) = 0
        

            /* Flowlight */
            _FlowlightColor("Flowlight Color", Color) = (1, 0, 0, 1)
            _Lengthlitandlar("LangthofLittle and Large", range(0,0.5)) = 0.005
            _MoveSpeed("MoveSpeed", float) = 5
            _Power("Power", float) = 1
            _LargeWidth("LargeWidth", range(0,0.005)) = 0.0035
            _LittleWidth("LittleWidth", range(0,0.001)) = 0.002

            /* --------- */
            _WidthRate("WidthRate",float) = 0
            _XOffset("XOffset",float) = 0
            _HeightRate("HeightRate",float) = 0
            _YOffset("YOffset",float) = 0

            /* UI */
            _StencilComp("Stencil Comparison", Float) = 8
            _Stencil("Stencil ID", Float) = 0
            _StencilOp("Stencil Operation", Float) = 0
            _StencilWriteMask("Stencil Write Mask", Float) = 255
            _StencilReadMask("Stencil Read Mask", Float) = 255
            _ColorMask("Color Mask", Float) = 15
            [Toggle(UNITY_UI_ALPHACLIP)] _UseClipRect ("Use Clip Rect", Float) = 0
            /* -- */


    }

    SubShader
    {
        Tags
        {
            "Queue" = "Transparent"
            "IgnoreProjector" = "True" // 忽略投影，因为是UI
            "RenderType" = "Transparent"
            "PreviewType" = "Plane"
            "CanUseSpriteAtlas" = "True"
        }

        Cull     Off
        Lighting Off
        ZWrite   Off
        Blend One OneMinusSrcAlpha
        ColorMask[_ColorMask]
        

        /* UI */
        Stencil
        {
            Ref[_Stencil]
            Comp[_StencilComp]
            Pass[_StencilOp]
            ReadMask[_StencilReadMask]
            WriteMask[_StencilWriteMask]
        }

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #pragma multi_compile _ PIXELSNAP_ON

            #include "UnityCG.cginc"

            struct appdata_t
            {
                float4 vertex : POSITION;
                float4 color : COLOR;
                float2 texcoord : TEXCOORD0;
            };

            struct v2f
            {
                float4 vertex : SV_POSITION;
                fixed4 color : COLOR;
                half2 texcoord : TEXCOORD0;
                float4 worldPosition: TEXCOORD1;
            };

            fixed4 _Color;
            /* Flowlight */
            float _Power;
            float _LargeWidth;
            float _LittleWidth;
            float _Lengthlitandlar;
            float _MoveSpeed;
            fixed4 _FlowlightColor;
            /* --------- */
            float _UVPosX;

            v2f vert(appdata_t IN)
            {
                v2f OUT;
                OUT.worldPosition = IN.vertex;
                OUT.vertex = UnityObjectToClipPos(IN.vertex);
                OUT.texcoord = IN.texcoord;
                OUT.color = IN.color * _Color;
                #ifdef PIXELSNAP_ON
                        OUT.vertex = UnityPixelSnap(OUT.vertex);
                #endif

                return OUT;
            }

            sampler2D _MainTex;
            float4 _MainTex_ST;
            float _WidthRate;
            float _XOffset;
            float _HeightRate;
            float _YOffset;


            bool _UseClipRect;
            float4 _ClipRect;
            float _ClipSoftX;
            float _ClipSoftY;

            // fixed _Factor;


            fixed4 frag(v2f IN) : SV_Target
            {
                fixed4 c = tex2D(_MainTex, IN.texcoord);

                /*使用裁剪*/
                if (_UseClipRect)
                {
                    float2 factor = float2(0.0, 0.0);
                    float2 tempXY = (IN.worldPosition.xy - _ClipRect.xy) / float2(_ClipSoftX, _ClipSoftY) * step(_ClipRect.xy, IN.worldPosition.xy);
                    factor = max(factor, tempXY);
                    float2 tempZW = (_ClipRect.zw - IN.worldPosition.xy) / float2(_ClipSoftX, _ClipSoftY) * step(IN.worldPosition.xy, _ClipRect.zw);
                    factor = min(factor, tempZW);
                    c.a *= clamp(min(factor.x, factor.y), 0.0, 1.0);
                }

                /* Flowlight */                
                // _UVPosX = _XOffset + (fmod(_Time.x * _MoveSpeed, 1) * 2 - 0.5) * _WidthRate;
                _UVPosX = _XOffset + (fmod(_Time.x * _MoveSpeed, 1) * 2 - 0.5); // 【-0.5, 1.5f】

                //标准uvX倾斜
                // _UVPosX += (IN.texcoord.y - _HeightRate * 0.5 - _YOffset) * 0.2;
                //以下是计算流光在区域内的强度，根据到标准点的距离的来确定强度，为了使变化更柔和非线性，使用距离平方或者sin函数也可以
                float lar = pow(1 - _LargeWidth * _WidthRate, 2);
                float lit = pow(1 - _LittleWidth * _WidthRate, 2);

                //第一道流光，可以累加任意条，如下
                fixed4 cadd = _FlowlightColor * saturate((1 - saturate(pow(_UVPosX - IN.texcoord.x,2))) - lar) * _Power / (1 - lar);
                cadd += _FlowlightColor * saturate((1 - saturate(pow(_UVPosX - _Lengthlitandlar * _WidthRate - IN.texcoord.x, 2))) - lit) * _Power / (1 - lit);

                c.rgb += cadd.rgb;
                c.rgb *= c.a;

                return c;
            }
            ENDCG
        }

    }
}