AppExperiments

Shader "Unlit/Outline Only" {
  Properties {
    _Color   ("Color",         Color) = (1,1,1,1)
    _Outline ("Outline Color", Color) = (1,1,1,1)
    _Width   ("Outline Width", Float) = 0.01
  }

  CGINCLUDE
  #include "UnityCG.cginc"
  #pragma fragmentoption ARB_precision_hint_fastest
  #pragma target 2.0

  float4 _Color;
  float4 _Outline;
  float _Width;

  struct appdata {
    float4 vertex : POSITION;
    float3 normal : NORMAL;
  };

  struct v2f_n {
    float4 vertex : SV_POSITION;
    float3 normal : TEXCOORD0;
  };

  struct v2f {
    float4 vertex : SV_POSITION;
  };

  v2f_n vert_rev_extrude(appdata v) {
    v2f_n o;
    o.vertex = UnityObjectToClipPos(v.vertex + float4(_Width * -1.0 * v.normal, 0));
    o.normal = v.normal;
    return o;
  }

  v2f vert(appdata v) {
    v2f o;
    o.vertex = UnityObjectToClipPos(v.vertex);
    return o;
  }

  v2f vert_extrude(appdata v) {
    v2f o;
    o.vertex = UnityObjectToClipPos(v.vertex + float4(_Width * 1.0 * v.normal, 0));
    return o;
  }

  fixed4 frag(v2f_n i) : SV_Target {
    fixed4 color = fixed4(1,1,1,1);
    float litAmount = dot(normalize(i.normal.xyz), normalize(float3(1, 1.3, 0)));
    color = litAmount * 0.25 + color;
    color *= _Color;
    return color;
  }

  fixed4 frag_outline(v2f i) : SV_Target{
    return _Outline;
  }

  ENDCG

	SubShader {
		Tags { "Queue"="Transparent" "RenderType"="Opaque" }
		LOD 100

    Pass {
      Cull Back
      ColorMask 0

      CGPROGRAM
      #pragma vertex vert
      #pragma fragment frag
      ENDCG
    }

    Pass{
      Cull Front

      CGPROGRAM
      #pragma vertex vert_extrude
      #pragma fragment frag_outline
      ENDCG
    }
	}
}