示例

Shader "Custom/NormalTest"
{
	Properties
	{
		_MainTex ("Texture", 2D) = "white" {}
		_Cutoff ("Cut", Range(0,1)) = 0.5
	}
	SubShader
	{
		LOD 100

		Pass
		{
			Tags { "RenderType"="Transparent" }

			ZWrite On
			ZTest LEqual

			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;
			
			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 col = tex2D(_MainTex, i.uv);
				return col;
			}
			ENDCG
		}

		Pass
		{
			Tags { "RenderType"="Transparent" }

			Blend SrcAlpha OneMinusSrcAlpha
			ZWrite On
			ZTest Greater

			CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag
			
			#include "UnityCG.cginc"

			struct appdata
			{
				float4 vertex : POSITION;
				//模型空间法线
				float3 normal : NORMAL;
				float2 uv : TEXCOORD0;
			};

			struct v2f
			{
				float2 uv : TEXCOORD0;
				float4 vertex : SV_POSITION;
				//世界空间法线
				float3 worldNormal : TEXCOORD1;
				//世界空间坐标
				float3 worldPosition : TEXCOORD2;
			};

			sampler2D _MainTex;
			float4 _MainTex_ST;
			fixed _Cutoff;
			
			v2f vert (appdata v)
			{
				v2f o;
				o.vertex = UnityObjectToClipPos(v.vertex);
				o.uv = TRANSFORM_TEX(v.uv, _MainTex);
				o.worldNormal = UnityObjectToWorldNormal(v.normal);
				o.worldPosition = mul(unity_ObjectToWorld, v.vertex).xyz;
				return o;
			}
			
			fixed4 frag (v2f i) : SV_Target
			{
				fixed3 worldNormal = normalize(i.worldNormal);
				fixed3 viewDir = normalize(UnityWorldSpaceViewDir(i.worldPosition));
				fixed v = saturate(1-dot(viewDir, worldNormal));
				clip(v - _Cutoff);
				return fixed4(1, 0, 0, v);
			}
			ENDCG
		}
	}
}

效果