How to draw a line on a mesh edge using a shader

I tried a lot of different options, like a outline, a wireframe shader, but they all do not give the desired effect.
Shader "Custom/WireframeShader"
{
	Properties
	{
		_WireColor("Edges Color", Color) = (0,0,0,1)
		_WireThickness("Edge Thickness", RANGE(0, 800)) = 100
		_WireSmoothness("Edge Smoothness", RANGE(0, 20)) = 3
		_AlbedoColor("Albedo Color", Color) = (1,1,1,1)
		_MainTex("Albedo (RGB)", 2D) = "white" {}
	}

		SubShader
	{
		Tags{ "RenderType" = "Opaque" }
		LOD 200

		Pass
	{
		CGPROGRAM
		// Use shader model 3.0 target, to get nicer looking lighting
#pragma target 3.0

#include "UnityCG.cginc"

#pragma vertex vert
#pragma fragment frag
#pragma geometry geom

		uniform sampler2D _MainTex;
	uniform float4 _MainTex_ST;

	struct Input
	{
		float2 uv_MainTex;
	};

	fixed4 _WireColor;
	fixed4 _AlbedoColor;

	uniform float _WireThickness;
	uniform float _WireSmoothness;

	struct appdata
	{
		float4 vertex : POSITION;
		float2 texcoord0 : TEXCOORD0;
		UNITY_VERTEX_INPUT_INSTANCE_ID
	};

	struct v2g
	{
		float4 projSpaceVertex : SV_POSITION;
		float2 uv0 : TEXCOORD0;
		float4 worldSpacePosition : TEXCOORD1;
		UNITY_VERTEX_OUTPUT_STEREO
	};

	struct g2f
	{
		float4 projSpaceVertex : SV_POSITION;
		float2 uv0 : TEXCOORD0;
		float4 worldSpacePosition : TEXCOORD1;
		float4 dist : TEXCOORD2;
		UNITY_VERTEX_OUTPUT_STEREO
	};

	v2g vert(appdata v)
	{
		v2g o;
		UNITY_SETUP_INSTANCE_ID(v);
		UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(o);
		o.projSpaceVertex = UnityObjectToClipPos(v.vertex);
		o.worldSpacePosition = mul(unity_ObjectToWorld, v.vertex);
		o.uv0 = TRANSFORM_TEX(v.texcoord0, _MainTex);
		return o;
	}


	[maxvertexcount(3)]
	void geom(triangle v2g i[3], inout TriangleStream<g2f> triangleStream)
	{
		float2 p0 = i[0].projSpaceVertex.xy / i[0].projSpaceVertex.w;
		float2 p1 = i[1].projSpaceVertex.xy / i[1].projSpaceVertex.w;
		float2 p2 = i[2].projSpaceVertex.xy / i[2].projSpaceVertex.w;

		float2 edge0 = p2 - p1;
		float2 edge1 = p2 - p0;
		float2 edge2 = p1 - p0;

		float area = abs(edge1.x * edge2.y - edge1.y * edge2.x);
		float wireThickness = 800 - _WireThickness;

		g2f o;

		o.uv0 = i[0].uv0;
		o.worldSpacePosition = i[0].worldSpacePosition;
		o.projSpaceVertex = i[0].projSpaceVertex;
		o.dist.xyz = float3((area / length(edge0)), 0.0, 0.0) * o.projSpaceVertex.w * wireThickness;
		o.dist.w = 1.0 / o.projSpaceVertex.w;
		UNITY_TRANSFER_VERTEX_OUTPUT_STEREO(i[0], o);
		triangleStream.Append(o);

		o.uv0 = i[1].uv0;
		o.worldSpacePosition = i[1].worldSpacePosition;
		o.projSpaceVertex = i[1].projSpaceVertex;
		o.dist.xyz = float3(0.0, (area / length(edge1)), 0.0) * o.projSpaceVertex.w * wireThickness;
		o.dist.w = 1.0 / o.projSpaceVertex.w;
		UNITY_TRANSFER_VERTEX_OUTPUT_STEREO(i[1], o);
		triangleStream.Append(o);

		o.uv0 = i[2].uv0;
		o.worldSpacePosition = i[2].worldSpacePosition;
		o.projSpaceVertex = i[2].projSpaceVertex;
		o.dist.xyz = float3(0.0, 0.0, (area / length(edge2))) * o.projSpaceVertex.w * wireThickness;
		o.dist.w = 1.0 / o.projSpaceVertex.w;
		UNITY_TRANSFER_VERTEX_OUTPUT_STEREO(i[2], o);
		triangleStream.Append(o);
	}

	fixed4 frag(g2f i) : SV_Target
	{
		float minDistanceToEdge = min(i.dist[0], min(i.dist[1], i.dist[2])) * i.dist[3];

	float4 baseColor = _AlbedoColor * tex2D(_MainTex, i.uv0);

	// Early out if we know we are not on a line segment.
	if (minDistanceToEdge > 0.9)
	{
		return fixed4(baseColor.rgb,0);
	}

	// Smooth our line out
	float t = exp2(_WireSmoothness * -1.0 * minDistanceToEdge * minDistanceToEdge);
	fixed4 finalColor = lerp(baseColor, _WireColor, t);
	finalColor.a = t;

	return finalColor;
	}
		ENDCG
	}
	}
		FallBack "Diffuse"
}
For example, such a shader gives the following result:
[155099-безымянныи.png|155099]
How can I leave only the outer edges of the mesh?
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