Unity Shader 图片流光效果实现（纯计算方式）

Unity Shader 图片流光效果实现（纯计算方式）

shader源码如下

// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'

Shader "Custom/StreamerLight" {
    Properties{
        _MainTex("Texture", 2D) = "white" { }
        _Angle("Angle", Float) = 45     //光带的倾斜角度
        _Width("Width",Float)=0.65      //光带的宽度
        _Interval("Interval",Float)=3   //间隔时间
        _BeginTime("BeginTime",Float)=0 //开始时间
        _OffestX("OffestX",Float)=0.6   //光带边界的偏移量
        _LoopTime("LoopTime",Float)=0.7 //单次的循环时间
    }
        SubShader
    {
    Tags {"Queue" = "Transparent" "IgnoreProjector" = "True" "RenderType" = "Transparent"}
    Blend SrcAlpha OneMinusSrcAlpha
        AlphaTest Greater 0.1
        pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"

            half _Angle;
            half _Width;
            half _Interval;
            half _BeginTime;
            half _OffestX;
            half _LoopTime;

            sampler2D _MainTex;
            float4 _MainTex_ST;

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

            //顶点函数没什么特别的，和常规一样
            v2f vert(appdata_base v)
            {
                v2f o;
                   o.pos = UnityObjectToClipPos(v.vertex);
                o.uv = TRANSFORM_TEX(v.texcoord,_MainTex);
                return o;
            }

            //必须放在使用其的 frag函数之前，否则无法识别。
            //核心：计算函数，角度，uv,光带的x长度，间隔，开始时间，偏移，单次循环时间
             float inFlash(float angle,float2 uv,float xLength,int interval,int beginTime, float offX, float loopTime)
            {
                 //亮度值
                 float brightness = 0;

                 //倾斜角
                 float angleInRad = 0.0174444 * angle;

                 //当前时间
                 float currentTime = _Time.y;

                 //获取本次光照的起始时间
                 int currentTimeInt = _Time.y / interval;
                 currentTimeInt *= interval;

                 //获取本次光照的流逝时间 = 当前时间 - 起始时间
                 float currentTimePassed = currentTime - currentTimeInt;
                 if (currentTimePassed > beginTime)
                 {
                     //底部左边界和右边界
                     float xBottomLeftBound;
                     float xBottomRightBound;

                     //此点边界
                     float xPointLeftBound;
                     float xPointRightBound;

                     float x0 = currentTimePassed - beginTime;
                     x0 /= loopTime;

                     //设置右边界
                     xBottomRightBound = x0;

                     //设置左边界
                     xBottomLeftBound = x0 - xLength;

                     //投影至x的长度 = y/ tan(angle)
                     float xProjL;
                     xProjL = (uv.y) / tan(angleInRad);

                     //此点的左边界 = 底部左边界 - 投影至x的长度
                     xPointLeftBound = xBottomLeftBound - xProjL;
                     //此点的右边界 = 底部右边界 - 投影至x的长度
                     xPointRightBound = xBottomRightBound - xProjL;

                     //边界加上一个偏移
                     xPointLeftBound += offX;
                     xPointRightBound += offX;

                     //如果该点在区域内
                     if (uv.x > xPointLeftBound && uv.x < xPointRightBound)
                     {
                         //得到发光区域的中心点
                         float midness = (xPointLeftBound + xPointRightBound) / 2;

                         //趋近中心点的程度，0表示位于边缘，1表示位于中心点
                         float rate = (xLength - 2 * abs(uv.x - midness)) / (xLength);
                         brightness = rate;
                     }
                 }
                 brightness = max(brightness,0);
                 brightness = min(brightness, 0.75);

                 //返回颜色 = 纯白色 * 亮度
                 float4 col = float4(1,1,1,1) *brightness;
                 return brightness;
             }

             float4 frag(v2f i) : COLOR
             {
                  float4 outp;

             //根据uv取得纹理颜色，和常规一样
            float4 texCol = tex2D(_MainTex,i.uv);

            //传进i.uv等参数，得到亮度值
            float tmpBrightness;
            tmpBrightness = inFlash(_Angle,i.uv,_Width,_Interval,_BeginTime,_OffestX,_LoopTime);

            //图像区域，判定设置为 颜色的A > 0.5,输出为材质颜色+光亮值
            if (texCol.w > 0.5)
                    outp = texCol + float4(1,1,1,1)*tmpBrightness;
            //空白区域，判定设置为 颜色的A <=0.5,输出空白
            else
                outp = float4(0,0,0,0);

            return outp;
            }
        ENDCG
    }
    }
}