Shader "UltraCombos/Composite"
{
    Properties
    {
        _LeftTex   ("Left",   2D) = "black" {}
        _CenterTex ("Center", 2D) = "black" {}
        _RightTex  ("Right",  2D) = "black" {}
     }

     SubShader
     {
        Blend One Zero

        Pass
        {
            Name "Composite"

            CGPROGRAM
            #include "UnityCustomRenderTexture.cginc"
            #pragma vertex CustomRenderTextureVertexShader
            #pragma fragment frag
            #pragma target 3.0

            sampler2D _LeftTex;
            sampler2D _CenterTex;
            sampler2D _RightTex;

            float4 frag(v2f_customrendertexture IN) : SV_Target
            {
                float2 uv = IN.localTexcoord.xy;
                float  x  = uv.x;
                const float third = 1.0 / 3.0;

                if (x < third)
                    return tex2D(_LeftTex,   float2(x * 3.0, uv.y));
                else if (x < 2.0 * third)
                    return tex2D(_CenterTex, float2((x - third) * 3.0, uv.y));
                else
                    return tex2D(_RightTex,  float2((x - 2.0 * third) * 3.0, uv.y));
            }
            ENDCG
        }
    }
}