Unity Shader--Alpha Test

Alpha测试：

符合条件的alpha像素显示出来，不符合的丢弃掉

AlphaTest Greater 0.5

AlphaTest Always 0.5表示关闭测试，总是通过

AlphaTest Never 0.5 表示总是不通过，不会渲染出来

变化参数

_AlphaCut("Alpha cut", float) = 0.5

AlphaTest Greater [_AlphaCut]

shader1.0中Alpha Test代码在如下：

Shader "Unlit/AlphaShader"
{
	Properties
	{
		_MainTex ("Texture", 2D) = "white" {}
		_AlphaCut("Alpha cut", float) = 0.5
	}
	SubShader
	{
		//打开AlphaTest
		//AlphaTest Greater 0.5
		//AlphaTest Never 0.5
		AlphaTest Greater [_AlphaCut]

		Pass
		{
			SetTexture[_MainTex]
			{
				combine texture
			}
		}
	}
}

运行效果图：

AlphaTest在shader2.0中不起作用，因为2.0中可以对纹理进行采样变成，所以不需要进行AlphaTest，就可以直接获取到alpha值

代码如下：

Shader "Unlit/AlphaTest2.0shader"
{
	Properties
	{		
		_MainTex ("Texture", 2D) = "white" {}
	}
	SubShader
	{
		AlphaTest Greater 0.5
		Blend SrcAlpha OneMinusSrcAlpha

		Pass
		{
			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 = mul(UNITY_MATRIX_MVP, v.vertex);
				o.uv = v.uv;
				return o;
			}
			
			fixed4 frag (v2f i) : SV_Target
			{
				
				fixed4 col = tex2D(_MainTex, i.uv);
				
				if (col.a < 0.5)
				{
					return fixed4(0, 0, 0, 0);
				}
				else
				{
					return col;
				}
				return col;
			}
			ENDCG
		}
	}
}

运行效果图：