// 1:09 https://www.youtube.com/watch?v=LhqI_yj3zO0 
Shader "Erika/Unit/ImageEffect/unit_img_motionBlur"
{
    Properties
    {
		_MainTex("Texture", 2D) = "white" {}
		_Angle("Angle", float) = 0
		_Distance("Distance", float) = 0
    }
    SubShader
    {
        Tags { "RenderType"="Opaque" "Queue" = "Transparent-1"}
        LOD 100

		ZWrite Off
		ZTest LEqual

		Blend SrcAlpha OneMinusSrcAlpha

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

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

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

            sampler2D _MainTex;
            float4 _MainTex_ST;

            float _Angle;

			fixed _Distance;

            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = TRANSFORM_TEX(v.uv, _MainTex);
                return o;
            }

            fixed4 frag (v2f i) : SV_Target
            {
                fixed2 uv = i.uv;
                fixed2 offset = fixed2(0.05, 0.05);
                const float sampleCount = 30;
                fixed4 color = fixed4(0,0,0,0);
                float radian = radians(_Angle);
                float distance = _Distance;
                for(int i = 0; i < sampleCount; i++)
				{
                    float dx = distance * cos(radian) / sampleCount * i;
                    float dy = distance * sin(radian) / sampleCount * i;
                    color += tex2D(_MainTex,float2(uv.x + dx,uv.y + dy)) * (1 / sampleCount);
                }
				//color.rgb *= 0.5f;
				return color;
            }
            ENDCG
        }
    }
}