unity shader 透明的描边效果 镂空描边 空心描边

效果：

代码：

// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'

// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'

// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'

Shader "Unlit/outline"
{
	Properties
	{
		_MainTex ("Texture", 2D) = "white" {}
		_Factor("宽度", float) = 0
		_Color("边缘颜色", Color) = (0,0,0,1)
	}
	SubShader
	{
		LOD 100
		tags {"Queue" = "Transparent"}
		Pass
		{
			ZWrite On
			ColorMask 0
		}

		Pass
		{	
			Tags{  "LightMode" = "ForwardBase" }
			Blend SrcAlpha OneMinusSrcAlpha
			ZWrite Off
			Cull Back        // 剔除背面
			CGPROGRAM
			//ZWrite Off
			#pragma vertex vert
			#pragma fragment frag
			// make fog work
			#pragma multi_compile_fog
			
			#include "UnityCG.cginc"
			struct appdata
			{
				float4 vertex : POSITION;
				float2 uv : TEXCOORD0;
			};

			struct v2f
			{
				float2 uv : TEXCOORD0;
				UNITY_FOG_COORDS(1)
				float4 vertex : SV_POSITION;
			};

			sampler2D _MainTex;
			float4 _MainTex_ST;
			
			v2f vert (appdata v)
			{
				v2f o;
				o.vertex = UnityObjectToClipPos(v.vertex);
				o.uv = TRANSFORM_TEX(v.uv, _MainTex);
				UNITY_TRANSFER_FOG(o,o.vertex);
				o.vertex.z;
				return o;
			}
			
			fixed4 frag (v2f i) : SV_Target
			{
				// sample the texture
				fixed4 col = tex2D(_MainTex, i.uv);
				// apply fog
				UNITY_APPLY_FOG(i.fogCoord, col);
				//discard;
				return float4(col.xyz, 0.2);
			}
			ENDCG
		}

		Pass
		{
			Tags{ "Queue" = "Geometry" "LightMode" = "ForwardBase" }
			Cull Front   //剔除正面
			ZWrite On
							//Offset -300, -5
			CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag
			#include "UnityCG.cginc"
			struct v2f
			{
				float4 vetex : POSITION;
			};
			float _Factor;
			half4 _Color;
			v2f vert(appdata_full data)
			{
				v2f o;
				float4 view_vetex = UnityObjectToClipPos(data.vertex);
				float3 view_normal = mul(UNITY_MATRIX_IT_MV, data.normal);
				float2 offset = mul(UNITY_MATRIX_P, view_normal.xy);
				o.vetex = view_vetex;
				o.vetex.xy += offset * _Factor;
				//o.vetex = UnityObjectToClipPos(data.vertex);
				//o.vetex.z += 0.01;
				return o;
			}
			half4 frag(v2f o) :COLOR
			{
				return _Color;
			}

			ENDCG
		}
	}
}

方法：
主要用到了三个Pass
第一个pass负责写入深度，
第二个正常渲染
第三个则进行法线延伸来产生描边效果，由于第一个pass已经写入深度缓冲，因此，在此Pass渲染时有部分会被剔除。