Gradient Shader

Shader "Cale/TweenGradient" {
    Properties {
        _color1 ("Grad 1 Color 1", Color) = (1,.5,.5,1)
        _color2 ("Grad 1 Color 2", Color) = (.5,1,1,1)
        _color3 ("Grad 2 Color 1", Color) = (.5,1,.5,1)
        _color4 ("Grad 2 Color 2", Color) = (.5,.5,1,1)
        _inter("Interpolation",Range(0,1))=0
        _MainTex ("Mask Texture", 2D) = "white"{}
    }
    Category{
        Blend SrcAlpha OneMinusSrcAlpha
        Tags {Queue=Transparent}
        SubShader {
            Pass{

                CGPROGRAM
// Upgrade NOTE: excluded shader from DX11 and Xbox360; has structs without semantics (struct v2f members uv_MainTex)
#pragma exclude_renderers d3d11 xbox360
                #pragma vertex vert
                #pragma fragment frag

                float4 _color1;
                float4 _color2;
                float4 _color3;
                float4 _color4;
                float _inter;
                sampler2D _MainTex;

                struct appdata {
                    float4 vertex : POSITION;
                    float4 tex : TEXCOORD0;
                    float3 normal : NORMAL;
                };
                struct v2f {
                    float4 vertex : TEXCOORD;
                    float4 pos : POSITION;
                    float4 color : COLOR;
                    float2 uv_MainTex;
                };
                v2f vert(appdata v) {
                    v2f o;
                    o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
                    o.vertex = v.tex;
                    return o;
                };

                half4 frag(v2f i) : COLOR {
                    _color1.r = (_color1.r*i.vertex.y+_color2.r*(1-i.vertex.y))*_inter+ (_color3.r*i.vertex.y+_color4.r*(1-i.vertex.y))*(1-_inter);
                    _color1.g = (_color1.g*i.vertex.y+_color2.g*(1-i.vertex.y))*_inter+ (_color3.g*i.vertex.y+_color4.g*(1-i.vertex.y))*(1-_inter);
                    _color1.b = (_color1.b*i.vertex.y+_color2.b*(1-i.vertex.y))*_inter+ (_color3.b*i.vertex.y+_color4.b*(1-i.vertex.y))*(1-_inter);
                    _color1.a = tex2D(_MainTex,i.vertex.xy).a;

                    return _color1;
                };

                ENDCG
            }
        }
    }
    FallBack "Diffuse"
}