Texture transition

TextureTransition.shader

Shader "Custom/TransitionCG"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
        _SecondTex("Second texture", 2D) = "white" {}
        _OpacityLevel("Opacity level", Range(0.0, 1.0)) = 0.0
    }
    SubShader
    {
        // No culling or depth
        Cull Off ZWrite Off ZTest Always

        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;
            };

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

            sampler2D _MainTex;
            sampler2D _SecondTex;
            Float _OpacityLevel;

            fixed4 frag (v2f i) : SV_Target
            {
                fixed4 col = tex2D(_MainTex, i.uv);
                fixed4 secCol = tex2D(_SecondTex, i.uv);
                return lerp(col, secCol, _OpacityLevel);
            }
            ENDCG
        }
    }
}