//对图片的mask处理,只有椭圆部分
Shader "Custom/InvertMask"
{
	Properties
	{
		_MainTex("Base (RGB), Alpha (A)", 2D) = "black" {}
		_CenterX("CenterX", float) = 0.5
		_CenterY("CenterY", float) = 0.5
		_Width("Width", float) = 0.5
		_Height("Height", float) = 0.15
		_LengthRate("LengthRate", float) = 0.1 
		_LengthRateTransition("LengthRateLerp", float) = 0.01
	}

		SubShader
		{
			LOD 200

			Tags
		{
			"Queue" = "Transparent"
			"IgnoreProjector" = "True"
			"RenderType" = "Transparent"
		}

			Pass
		{
			Cull Off
			Lighting Off
			ZWrite Off
			Fog{ Mode Off }
			Offset -1,-1
			Blend SrcAlpha OneMinusSrcAlpha

			CGPROGRAM
	#pragma vertex vert
	#pragma fragment frag            
	#include "UnityCG.cginc"

			sampler2D _MainTex;
		half4 _MainTex_ST;
		half _CenterX;
		half _CenterY;
		half _Width;
		half _Height;
		half _LengthRate;
		half _LengthRateTransition;

		struct appdata_t
		{
			half4 vertex : POSITION;
			half2 texcoord : TEXCOORD0;
			fixed4 color : COLOR;
		};

		struct v2f
		{
			half4 vertex : SV_POSITION;
			half2 texcoord : TEXCOORD0;
			fixed4 color : COLOR;
		};

		v2f o;

		v2f vert(appdata_t v)
		{
			o.vertex = UnityObjectToClipPos(v.vertex);
			o.texcoord = v.texcoord;
			o.color = v.color;
			return o;
		}

		fixed4 frag(v2f IN) : COLOR
		{
			half2 pt = IN.texcoord - half2(_CenterX,(1 - _CenterY));
			half h = (pt.x*pt.x) / (_Width*_Width) + (pt.y*pt.y) / (_Height*_Height);

			half4  c = tex2D(_MainTex, IN.texcoord) * IN.color;
			half sub = _LengthRate - h;
			if (h < _LengthRate && sub < _LengthRateTransition)
			{
				c.a = c.a - sub / _LengthRateTransition ;
				return c;
			}
			else if (h < _LengthRate)
			{
				discard;
			}

			return c;
		}
			ENDCG
		}
		}

			SubShader
		{
			LOD 100

			Tags
		{
			"Queue" = "Transparent"
			"IgnoreProjector" = "True"
			"RenderType" = "Transparent"
		}

			Pass
		{
			Cull Off
			Lighting Off
			ZWrite Off
			Fog{ Mode Off }
			Offset -1,-1
			ColorMask RGB
			Blend SrcAlpha OneMinusSrcAlpha
			ColorMaterial AmbientAndDiffuse

			SetTexture[_MainTex]
		{
			Combine Texture * Primary
		}
		}
		}
}