Undeclared identifier Error in desaturate shader

Unity Engine
1

Hello community!
I am very new to shader and google did not help me this time.
Is anyone here can point me into the problem please?
so here is the shader
I get an Undeclared identifier “_MainTex” at line 103 (on metal)

Shader "Sprites/Desaturate"
{
    Properties
    {
        [PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {}
        _Color ("Tint", Color) = (1,1,1,1)
        _Saturate ("Saturate", Range (0, 1)) = 1
        _Bright ("Brightness", Float) = 0
        [MaterialToggle] PixelSnap ("Pixel snap", Float) = 0
       
        // required for UI.Mask
        _StencilComp ("Stencil Comparison", Float) = 8
        _Stencil ("Stencil ID", Float) = 0
        _StencilOp ("Stencil Operation", Float) = 0
        _StencilWriteMask ("Stencil Write Mask", Float) = 255
        _StencilReadMask ("Stencil Read Mask", Float) = 255
        _ColorMask ("Color Mask", Float) = 15

        [Toggle(UNITY_UI_ALPHACLIP)] _UseUIAlphaClip ("Use Alpha Clip", Float) = 0
    }

    SubShader
    {
        Tags
        {
            "Queue"="Transparent"
            "IgnoreProjector"="True"
            "RenderType"="Transparent"
            "PreviewType"="Plane"
            "CanUseSpriteAtlas"="True"
        }
                Stencil
        {
            Ref [_Stencil]
            Comp [_StencilComp]
            Pass [_StencilOp]
            ReadMask [_StencilReadMask]
            WriteMask [_StencilWriteMask]
         }

        Cull Off
        Lighting Off
        ZWrite Off
        Fog { Mode Off }
        Blend One OneMinusSrcAlpha

        Pass
        {
//            Stencil {
//                Ref 2
//                Comp Less
//                Pass keep
//                Fail decrWrap
//                ZFail keep
//            }
        CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #pragma multi_compile DUMMY PIXELSNAP_ON
            #include "UnityCG.cginc"
           
            struct appdata_t
            {
                float4 vertex   : POSITION;
                float4 color    : COLOR;
//                float saturation: FLOAT;
                float2 texcoord : TEXCOORD0;
            };

            struct v2f
            {
                float4 vertex   : SV_POSITION;
                fixed4 color    : COLOR;
                float saturation: FLOAT;
                fixed brightness: FIXED;
                half2 texcoord  : TEXCOORD0;
            };
           
            fixed4 _Color;
            fixed _Saturate;
            fixed _Bright;
           
            v2f vert(appdata_t IN)
            {
                v2f OUT;
                OUT.vertex = UnityObjectToClipPos(IN.vertex);
                OUT.texcoord = IN.texcoord;
                OUT.color = IN.color * _Color;
                OUT.saturation = _Saturate;
                OUT.brightness = _Bright;
                #ifdef PIXELSNAP_ON
                OUT.vertex = UnityPixelSnap (OUT.vertex);
                #endif

                return OUT;
            }


            fixed4 frag(v2f IN) : SV_Target
            {
                float luminance = (tex2D(_MainTex, IN.texcoord).r + tex2D(_MainTex, IN.texcoord).g + tex2D(_MainTex, IN.texcoord).b)/3.0;
                fixed4 colorSature = fixed4(lerp(luminance, tex2D(_MainTex, IN.texcoord).r, IN.saturation) + IN.brightness,    lerp(luminance, tex2D(_MainTex, IN.texcoord).g, IN.saturation) + IN.brightness, lerp(luminance, tex2D(_MainTex, IN.texcoord).b, IN.saturation) + IN.brightness, tex2D(_MainTex, IN.texcoord).a);
                fixed4 c = colorSature * IN.color;
                c.rgb *= c.a;
                return c;
            }
        ENDCG
        }
    }
}
2

Hi guys I figured it out

it misses a line name of the variable in the pass of shader
sampler2D _MainTex;

1 Like
3

I have the same problem, how did you fix it?

found it, need to add “sampler2D _MainTex;” somewhere. looked here: