それぞれ同じようなエフェクト(もとのマスク画像を加算するかどうかの違い)

UIFade1.shader

Shader "MBL/UI/UIFade"
{
	Properties
	{
		[HideInInspector]
		_MainTex ("Texture", 2D) = "white" {}
		_BGTex("BGTexture", 2D) = "white" {}
		_Clip ("Clip", Range(0,1)) = 0
		_SrcCol ("SourceColor", Color) = (0,0,0,1)
		_DstCol ("DestinationColor", Color) = (1,1,1,1)
		_Blend ("Blend", Float) = 0.5
	}
	SubShader
	{
		Blend SrcAlpha OneMinusSrcAlpha
		Tags{"Queue"="Transparent" "PreviewType"="Plane"}

		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;
			sampler2D _BGTex;
			float _Clip;
			float4 _SrcCol;
			float4 _DstCol;
			float _Blend;

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

			fixed4 frag (v2f i) : SV_Target
			{
				float4 mask = tex2D(_MainTex, i.uv);
				float4 bg = tex2D(_BGTex, i.uv);
				clip(mask.a - _Clip);
				float4 col = lerp(_SrcCol, _DstCol, i.uv.x * i.uv.y);
				mask += (col * bg) * _Blend;
				mask.a = 1 - _Clip;
				return mask;
			}
			ENDCG
		}
	}
}

UIFade2.shader

Shader "MBL/UI/UIFade"
{
	Properties
	{
		[HideInInspector]
		_MainTex ("Texture", 2D) = "white" {}
		_BGTex("BGTexture", 2D) = "white" {}
		_Clip ("Clip", Range(0,1)) = 0
		_SrcCol ("SourceColor", Color) = (0,0,0,1)
		_DstCol ("DestinationColor", Color) = (1,1,1,1)
		_Blend ("Blend", Float) = 0.5
	}
	SubShader
	{
		Blend SrcAlpha OneMinusSrcAlpha
		Tags{"Queue"="Transparent" "PreviewType"="Plane"}

		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;
			sampler2D _BGTex;
			float _Clip;
			float4 _SrcCol;
			float4 _DstCol;
			float _Blend;

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

			fixed4 frag (v2f i) : SV_Target
			{
				float4 mask = tex2D(_MainTex, i.uv);
				float4 bg = tex2D(_BGTex, i.uv);
				clip(mask.a - _Clip);
				float4 col = lerp(_SrcCol, _DstCol, i.uv.x * i.uv.y);
				mask = (col * bg) * _Blend;
				mask.a = 1 - _Clip;
				return mask;
			}
			ENDCG
		}
	}
}