- AlphaTest
上图为简单的AlphaTest，Alpha值小于0.55的颜色抛弃。判断的语法clip (texcoordColor.a - value)也可写作123456789101112131415if((texcoordColor.a - value) < 0.0){discard;}```- 双面渲染AlphaTest开启双面渲染也比较容易，只需要在`Tags={ "LightMode"="ForwardBase" }`后添加一行`Cull Off`, 关闭剔除即可开启双面渲染。# 2. 透明混合(AlphaBlend)- AlphaBlend在Pass中开启Blend即可开启透明混合，混合的公式为`混合颜色 = 当前物体Alpha * 当前颜色 + (1 - 当前Alpha) * 背景颜色`- AlphaBlendZWriteAlphaBlend的shader添加一个Pass即可开启深度写入
Pass
{
ZWrite On
ColorMask 0
}
`ColorMask 0`即关闭该Pass的颜色通道写入，即该Pass只执行了深度写入，然后在后续Pass中处理其他操作。开启ZWrite以后相比AlphaBlend关闭ZWrite能更好地体现前后关系。
- 双面渲染
AlphaBlend的双面渲染要比AlphaTest的稍微复杂一些, 复制原来AlphaBlend的代码，写作2个Pass，分别剔除Front渲染背面和剔除Back渲染前面。
Pass
{
Cull Front
//原来AlphaBlend的代码
}
Pass
{
Cull Back
//原来AlphaBlend的代码
}
- Photoshop中AlphaBlend的几种常用模式
>//正常(Normal)，透明度混合
Blend SrcAlpha OneMinusSrcAlpha
>
>//柔和相加(Soft Additive)
Blend OneMinusDstColor One
>
>//正片叠底(multiply 相乘)
Blend DstColor One
>
>//变暗(Darken)
BlendOp Min
Blend One One
>
>//变亮(Lighten)
BlendOp Max
Blend One One
>
>//滤色(Screen)
Blend OneMinusDstColor One
>>//等同于Blend One OneMinusSrcColor
//等于D + S - D * S
>
>线性减淡(Linear Dodge)
Blend One One
Shader “UnityShaderLearning/AlphaTest”
{
Properties
{
_Color (“Main Tint”, Color) = (1, 1, 1, 1)
_MainTex (“Main Tex”, 2D) = “white”{}
_Cutoff (“Alpha Cutoff”, Range(0, 1)) = 0.55
}
SubShader
{
Tags { “Queue”=”AlphaTest” “IgnoreProjector” = “True” “RenderType”=”TransparentCutout”}
Pass
{
Tags { "LightMode"="ForwardBase" }
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "Lighting.cginc"
fixed4 _Color;
sampler2D _MainTex;
float4 _MainTex_ST;
fixed _Cutoff;
struct a2v
{
float4 vertex : POSITION;
float3 normal : NORMAL;
float4 texcoord : TEXCOORD0;
};
struct v2f
{
float4 pos : SV_POSITION;
float3 worldNormal : TEXCOORD0;
float3 worldPos : TEXCOORD1;
float2 uv : TEXCOORD2;
};
v2f vert(a2v v)
{
v2f o;
o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
o.worldNormal = UnityObjectToWorldNormal(v.normal);
o.worldPos = mul(_Object2World, v.vertex).xyz;
o.uv = TRANSFORM_TEX(v.texcoord, _MainTex);
return o;
}
fixed4 frag(v2f i) : SV_Target
{
fixed3 worldNormal = normalize(i.worldNormal);
fixed3 worldLightDir = normalize(UnityWorldSpaceLightDir(i.worldPos));
fixed4 texColor = tex2D(_MainTex, i.uv);
clip (texColor.a - _Cutoff);
fixed3 albedo = texColor.rgb * _Color.rgb;
fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.xyz * albedo;
fixed3 diffuse = _LightColor0.rgb * albedo * max(0, dot(worldNormal, worldLightDir));
return fixed4(ambient + diffuse, 1.0);
}
ENDCG
}
}
FallBack "Transparent/Cutout/VertexLit"
}
Shader “UnityShaderLearning/AlphaBlend”
{
Properties
{
_Color (“Main Tint”, Color) = (1, 1, 1, 1)
_MainTex (“Main Tex”, 2D) = “white”{}
_AlphaScale (“Alpha Scale”, Range(0, 1)) = 1
}
SubShader
{
Tags { "Queue"="AlphaTest" "IgnoreProjector"="True" "RenderType"="TransparentCutout"}
Pass
{
Tags { "LightMode"="ForwardBase" }
ZWrite Off
Blend SrcAlpha OneMinusSrcAlpha
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "Lighting.cginc"
fixed4 _Color;
sampler2D _MainTex;
float4 _MainTex_ST;
fixed _AlphaScale;
struct a2v
{
float4 vertex : POSITION;
float3 normal : NORMAL;
float4 texcoord : TEXCOORD0;
};
struct v2f
{
float4 pos : SV_POSITION;
float3 worldNormal : TEXCOORD0;
float3 worldPos : TEXCOORD1;
float2 uv : TEXCOORD2;
};
v2f vert(a2v v)
{
v2f o;
o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
o.worldNormal = UnityObjectToWorldNormal(v.normal);
o.worldPos = mul(_Object2World, v.vertex).xyz;
o.uv = TRANSFORM_TEX(v.texcoord, _MainTex);
return o;
}
fixed4 frag(v2f i) : SV_Target
{
fixed3 worldNormal = normalize(i.worldNormal);
fixed3 worldLightDir = normalize(UnityWorldSpaceLightDir(i.worldPos));
fixed4 texColor = tex2D(_MainTex, i.uv);
fixed3 albedo = texColor.rgb * _Color.rgb;
fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.xyz * albedo;
fixed3 diffuse = _LightColor0.rgb * albedo * max(0, dot(worldNormal, worldLightDir));
return fixed4(ambient + diffuse, texColor.a * _AlphaScale);
}
ENDCG
}
}
FallBack "Transparent/VertexLit"
}
```