Shader "Custom/FrontObject" 
{
    Properties {
        _MainTex ("Texture", 2D) = "white" {}
        _Color ("Color", Color) = (1,1,1,1)
        _SilhouetteColor ("silhouette Color", Color) = (0,1,0,1)
    }

    SubShader {
        Tags { "Queue"="Transparent-1" "IgnoreProjector"="True" "RenderType"="Transparent" }
        Lighting On 
        ZWrite Off 
        Fog { Mode Off }
        Blend SrcAlpha OneMinusSrcAlpha
        Cull Off

        Pass 
        {
            Stencil 
            {
                Ref 1
                Comp NotEqual
            }
            ColorMaterial AmbientAndDiffuse
            SetTexture [_MainTex] 
            {
                constantColor [_Color]
                combine texture * constant
            }
        }
        Pass {
            Stencil {
                Ref 1
                Comp Equal
            }
            Blend SrcAlpha OneMinusSrcAlpha

            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;
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;
            float4 _SilhouetteColor;
            
            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = TRANSFORM_TEX(v.uv, _MainTex);
                return o;
            }
            
            fixed4 frag (v2f i) : SV_Target
            {
                fixed4 basic = tex2D(_MainTex, i.uv);
                if(basic.a==0){
                    discard;
                }
                return _SilhouetteColor.rgba;
            }
            ENDCG

        }
    }
}