参考链接：
https://zhuanlan.zhihu.com/p/32561155
https://blog.csdn.net/WuShangLZ/article/details/80401441
https://www.jianshu.com/p/2d98fad196d2
内置shader下载方法：
https://jingyan.baidu.com/article/63acb44a1f598161fcc17efa.html
unity版本：2018.3.8f1
内置UI-Default.shader：
1 // Unity built-in shader source. Copyright (c) 2016 Unity Technologies. MIT license (see license.txt) 2 3 Shader "UI/Default" 4 { 5 Properties 6 { 7 [PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {} 8 _Color ("Tint", Color) = (1,1,1,1) 9 10 _StencilComp ("Stencil Comparison", Float) = 8 11 _Stencil ("Stencil ID", Float) = 0 12 _StencilOp ("Stencil Operation", Float) = 0 13 _StencilWriteMask ("Stencil Write Mask", Float) = 255 14 _StencilReadMask ("Stencil Read Mask", Float) = 255 15 16 _ColorMask ("Color Mask", Float) = 15 17 18 [Toggle(UNITY_UI_ALPHACLIP)] _UseUIAlphaClip ("Use Alpha Clip", Float) = 0 19 } 20 21 SubShader 22 { 23 Tags 24 { 25 "Queue"="Transparent" 26 "IgnoreProjector"="True" 27 "RenderType"="Transparent" 28 "PreviewType"="Plane" 29 "CanUseSpriteAtlas"="True" 30 } 31 32 Stencil 33 { 34 Ref [_Stencil] 35 Comp [_StencilComp] 36 Pass [_StencilOp] 37 ReadMask [_StencilReadMask] 38 WriteMask [_StencilWriteMask] 39 } 40 41 Cull Off 42 Lighting Off 43 ZWrite Off 44 ZTest [unity_GUIZTestMode] 45 Blend SrcAlpha OneMinusSrcAlpha 46 ColorMask [_ColorMask] 47 48 Pass 49 { 50 Name "Default" 51 CGPROGRAM 52 #pragma vertex vert 53 #pragma fragment frag 54 #pragma target 2.0 55 56 #include "UnityCG.cginc" 57 #include "UnityUI.cginc" 58 59 #pragma multi_compile __ UNITY_UI_CLIP_RECT 60 #pragma multi_compile __ UNITY_UI_ALPHACLIP 61 62 struct appdata_t 63 { 64 float4 vertex : POSITION; 65 float4 color : COLOR; 66 float2 texcoord : TEXCOORD0; 67 UNITY_VERTEX_INPUT_INSTANCE_ID 68 }; 69 70 struct v2f 71 { 72 float4 vertex : SV_POSITION; 73 fixed4 color : COLOR; 74 float2 texcoord : TEXCOORD0; 75 float4 worldPosition : TEXCOORD1; 76 UNITY_VERTEX_OUTPUT_STEREO 77 }; 78 79 sampler2D _MainTex; 80 fixed4 _Color; 81 fixed4 _TextureSampleAdd; 82 float4 _ClipRect; 83 float4 _MainTex_ST; 84 85 v2f vert(appdata_t v) 86 { 87 v2f OUT; 88 UNITY_SETUP_INSTANCE_ID(v); 89 UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(OUT); 90 OUT.worldPosition = v.vertex; 91 OUT.vertex = UnityObjectToClipPos(OUT.worldPosition); 92 93 OUT.texcoord = TRANSFORM_TEX(v.texcoord, _MainTex); 94 95 OUT.color = v.color * _Color; 96 return OUT; 97 } 98 99 fixed4 frag(v2f IN) : SV_Target 100 { 101 half4 color = (tex2D(_MainTex, IN.texcoord) + _TextureSampleAdd) * IN.color; 102 103 #ifdef UNITY_UI_CLIP_RECT 104 color.a *= UnityGet2DClipping(IN.worldPosition.xy, _ClipRect); 105 #endif 106 107 #ifdef UNITY_UI_ALPHACLIP 108 clip (color.a - 0.001); 109 #endif 110 111 return color; 112 } 113 ENDCG 114 } 115 } 116 }
1.模板测试
2.
UnityGet2DClipping的定义在UnityUI.cginc中：
1 inline float UnityGet2DClipping (in float2 position, in float4 clipRect) 2 { 3 float2 inside = step(clipRect.xy, position.xy) * step(position.xy, clipRect.zw); 4 return inside.x * inside.y; 5 }
step(a, x)：如果a>x，返回0；否则，返回1
clipRect：左下角为xy，右上角为zw
因此，也就是说，如果点不在clipRect中，则返回0
