How to make shader working right in UGUI mask?

Unity Engine
1

Environment: Unity 4.6.0p1 UGUI

Raw image:

Within mask:

And I have wrote a grayscale shader:

Shader "UI/GrayColor"
{
    Properties
    {
        _MainTex ("Sprite Texture", 2D) = "white" {}
        _GrayScale ("GrayScale", Range(0,1)) = 1
    }

    SubShader
    {
        Tags
        {
            "Queue"="Transparent"
            "IgnoreProjector"="True"
            "RenderType"="Transparent"
            "PreviewType"="Plane"
            "CanUseSpriteAtlas"="True"
        }
       
        Cull Off
        Lighting Off
        ZWrite Off
        ZTest [unity_GUIZTestMode]
        Fog { Mode Off }
        Blend SrcAlpha OneMinusSrcAlpha

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"
           
            struct appdata_t
            {
                float4 vertex   : POSITION;
                float2 texcoord : TEXCOORD0;
            };

            struct v2f
            {
                float4 vertex   : SV_POSITION;
                half2 texcoord  : TEXCOORD0;
            };
           
            v2f vert(appdata_t IN)
            {
                v2f OUT;
                OUT.vertex = mul(UNITY_MATRIX_MVP, IN.vertex);
                OUT.texcoord = IN.texcoord;
                return OUT;
            }
           
            sampler2D _MainTex;
            fixed _GrayScale;

            fixed4 frag(v2f IN) : SV_Target
            {
                half4 c = tex2D(_MainTex, IN.texcoord);
                fixed grayscale = Luminance(c.rgb);
                c.rgb = grayscale.xxx * _GrayScale;
                return c;
            }
            ENDCG
        }
    }
}

Make a grayscale material for Image:

Although grayscale image came out, but mask is broken. How can I fix this bug? Thank you.

2

I have a similar situation with a Mask object that has a image as child.
The image has a custom shader which causes it to ignore the Mask, im sure theres something simple to fix it but cant find it.
If anyone has an idea, please help!

3

Download the Unity built-in shaders and take a look at ā€œDefaultResourcesExtra/UI/UI-Default.shaderā€ for example. Itā€™s using Stencil, which is missing in your shader (along with a few other things). Stencil is probably used for masking in this context.

        Stencil
        {
            Ref [_Stencil]
            Comp [_StencilComp]
            Pass [_StencilOp]
            ReadMask [_StencilReadMask]
            WriteMask [_StencilWriteMask]
        }
1 Like
4

I have a question tooļ¼Affer adding ā€œStencil {ā€¦}ā€ I canā€™t adjust the UI image by shader when game runningļ¼