shader 圆形遮罩

unity 遮罩，用mask 试了试 没啥效果，于是上网找了关于shader遮罩的博客。效果还不错。



圆形裁剪。

步骤：

1. shader：其主要原理是把遮罩图片的透明和原图片的透明度进行混合。不透明部分就是遮罩区域，透明部分不再显示// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'

Shader "Unlit/Circle"
{
Properties
{
[PerRendererData] _MainTex("Sprite Texture", 2D) = "white" {}
_Mask("Base (RGB)", 2D) = "white" {}

_Color("Tint", Color) = (1,1,1,1)
_StencilComp("Stencil Comparison", Float) = 8
_Stencil("Stencil ID", Float) = 0
_StencilOp("Stencil Operation", Float) = 0
_StencilWriteMask("Stencil Write Mask", Float) = 255
_StencilReadMask("Stencil Read Mask", Float) = 255
_ColorMask("Color Mask", Float) = 15
[Toggle(UNITY_UI_ALPHACLIP)] _UseUIAlphaClip("Use Alpha Clip", Float) = 0
}

SubShader
{
Tags
{
"Queue" = "Transparent"
"IgnoreProjector" = "True"
"RenderType" = "Transparent"
"PreviewType" = "Plane"
"CanUseSpriteAtlas" = "True"
}

Stencil
{
Ref[_Stencil]
Comp[_StencilComp]
Pass[_StencilOp]
ReadMask[_StencilReadMask]
WriteMask[_StencilWriteMask]
}

Cull Off
Lighting Off
ZWrite Off
ZTest[unity_GUIZTestMode]
Blend SrcAlpha OneMinusSrcAlpha
ColorMask[_ColorMask]

Pass
{
CGPROGRAM
#pragma vertex vert
#pragma fragment frag

#include "UnityCG.cginc"
#include "UnityUI.cginc"

#pragma multi_compile __ UNITY_UI_ALPHACLIP

struct a2v
{
fixed2 uv : TEXCOORD0;
half4 vertex : POSITION;
float4 color : COLOR;
};

fixed4 _Color;

struct v2f
{
fixed2 uv : TEXCOORD0;
half4 vertex : SV_POSITION;
float4 color : COLOR;
};

sampler2D _MainTex;
sampler2D _Mask;

v2f vert(a2v i)
{
v2f o;
o.vertex = UnityObjectToClipPos(i.vertex);
o.uv = i.uv;

o.color = i.color * _Color;
return o;
}

fixed4 frag(v2f i) : COLOR
{
half4 color = tex2D(_MainTex, i.uv) * i.color;
half4 mask = tex2D(_Mask, i.uv);
color.a *= mask.a;
return color;
}
ENDCG
}
}
}

2.遮罩图片



除了圆形区域，其它地方是透明的，是为了用透明度和原图进行混合

3.新建材质



4.新建图片