// 动态模糊

Shader "Erika/Common/Image/MotionBlur" 
{
	Properties
	{
		_MainTex("Texture", 2D) = "white" {}
		_Angle("Angle", float) = 0
		_Distance("Distance", float) = 0
		_UnitTileOffset("TileOffset", Vector) = (1,1,0,0)
		_Iterate("Iterate Count", float) = 1
	}

	SubShader
	{
		Tags { "RenderType" = "Opaque" "Queue" = "Transparent-1"}
		LOD 100

		ZWrite Off
		ZTest LEqual

		Blend SrcAlpha OneMinusSrcAlpha

		Pass
		{
			CGPROGRAM
			#pragma vertex image_vert
			#pragma fragment frag

			#include "UnityCG.cginc"
			#include "./ImageEffect.cginc"

			float _Angle;
			fixed _Distance;
			float _Iterate; // 迭代次数
            float _AlphaMultiplier; //

			fixed4 frag(image_v2f i) : SV_Target
			{
			    _Distance = 0.1;

				fixed2 uv0 = i.uv;
				
                fixed4 color = fixed4(0,0,0,0);
                const float count = 20;
                float step = _Distance / count;
				float amount = 0.2f;
                for(int i = 0; i < count; ++i) 
                {
                    fixed2 uv = uv0 + step * i * fixed2(cos(radians(_Angle)), sin(radians(_Angle)));
                    if(uv.x > 1) continue;
                    if(uv.x < 0) continue;
                    float weight = amount - amount * ((float)i / (float)count);
                    color += tex2D(_MainTex, uv) * weight;
                }

                color.a *= _AlphaMultiplier;

				//color = fixed4(1,0,0,0.5f);
				
				return color;
			}
			ENDCG
		}
	}

} // shader