Shader "MY/MotionShadow"
{
	Properties
	{
		_MainTex("Texture", 2D) = "white" {}
		_BlurSize("BlurSize", Range(0.01, 0.99)) = 0.9
		_Offset("xy = uv zw = motion",Vector) = (0,0,0,0)
		_Brightness("Brightness", Range(0,10)) = 1
		_Flash("Flash", Range(0,1)) = 1
		_Alpha("Alpha",Range(0,1)) = 1
	}

		SubShader
		{
			Tags{ "RenderType" = "Opaque" }

			ZTest Off
			cull Off
			ZWrite Off
			Blend SrcAlpha OneMinusSrcAlpha

			Pass
			{
				Name "Main"
				CGPROGRAM
				#pragma vertex vert
				#pragma fragment frag

				#include "UnityCG.cginc"

				struct appdata {
					float4 vertex:POSITION;
					float2 uv:TEXCOORD0;
				};

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

				sampler2D _MainTex;
				half4 _Offset;
				half _BlurSize;
				half _Brightness;
				//half _Saturation;
				//half _Contrast;
				half _Flash;
				half _Alpha;

				v2f vert(appdata v)
				{
					v2f o;
					o.pos = UnityObjectToClipPos(v.vertex);
					o.uv = v.uv + _Offset.xy;
					return o;
				}

				fixed4 frag(v2f i) : SV_Target
				{
					fixed4 col = tex2D(_MainTex, i.uv);
				//降低中心人物的运动模糊start
				float r = length((i.uv.x - _Offset.z, i.uv.y - _Offset.w));
				float a = _BlurSize * pow((1 - r + 0.01), 2);
				col.a = max(a, 1 - _BlurSize);
				//降低中心人物的运动模糊end


				//亮度计算直接叠加
				half3 color = col.rgb*_Brightness;

				////饱和度和灰度有关，先计算最低灰度系数下的图像，随后对原始的图像进行插值操作
				//fixed3 gray = fixed3(0.2125, 0.7154, 0.0721);
				////点积得到最低灰度值，构成最低灰度图像
				//fixed minGray = dot(gray, col.rgb);
				//fixed3 grayColor = fixed3(minGray, minGray, minGray);
				////对灰度图像和原始图像插值操作以得到最终系数的显示图像
				//color = lerp(grayColor, color, _Saturation);

				//对比度效果类似，先计算最低对比度图像，即(0.5,0.5,0.5)，随后插值操作
				fixed3 flash = fixed3(1, 1, 1);
				color = lerp(color, flash, _Flash);

				////得到所有处理完成后的图像颜色，但alpha保持不变
				return fixed4(color, col.a * _Alpha);
			}
		ENDCG
		}

		}
}