[UnityShader基础]08.UI-Default.shader

参考链接：

https://zhuanlan.zhihu.com/p/32561155

https://blog.csdn.net/WuShangLZ/article/details/80401441

https://www.jianshu.com/p/2d98fad196d2

unity版本：2018.3.8f1

内置UI-Default.shader：

 // Unity built-in shader source. Copyright (c) 2016 Unity Technologies. MIT license (see license.txt)

 Shader "UI/Default"
 {
     Properties
     {
         [PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {}
         _Color ("Tint", Color) = (,,,)

         _StencilComp ("Stencil Comparison", Float) =
         _Stencil ("Stencil ID", Float) =
         _StencilOp ("Stencil Operation", Float) =
         _StencilWriteMask ("Stencil Write Mask", Float) =
         _StencilReadMask ("Stencil Read Mask", Float) = 

         _ColorMask ("Color Mask", Float) = 

         [Toggle(UNITY_UI_ALPHACLIP)] _UseUIAlphaClip ("Use Alpha Clip", Float) =
     }

     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
         {
             Name "Default"
         CGPROGRAM
             #pragma vertex vert
             #pragma fragment frag
             #pragma target 2.0

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

             #pragma multi_compile __ UNITY_UI_CLIP_RECT
             #pragma multi_compile __ UNITY_UI_ALPHACLIP

             struct appdata_t
             {
                 float4 vertex   : POSITION;
                 float4 color    : COLOR;
                 float2 texcoord : TEXCOORD0;
                 UNITY_VERTEX_INPUT_INSTANCE_ID
             };

             struct v2f
             {
                 float4 vertex   : SV_POSITION;
                 fixed4 color    : COLOR;
                 float2 texcoord  : TEXCOORD0;
                 float4 worldPosition : TEXCOORD1;
                 UNITY_VERTEX_OUTPUT_STEREO
             };

             sampler2D _MainTex;
             fixed4 _Color;
             fixed4 _TextureSampleAdd;
             float4 _ClipRect;
             float4 _MainTex_ST;

             v2f vert(appdata_t v)
             {
                 v2f OUT;
                 UNITY_SETUP_INSTANCE_ID(v);
                 UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(OUT);
                 OUT.worldPosition = v.vertex;
                 OUT.vertex = UnityObjectToClipPos(OUT.worldPosition);

                 OUT.texcoord = TRANSFORM_TEX(v.texcoord, _MainTex);

                 OUT.color = v.color * _Color;
                 return OUT;
             }

             fixed4 frag(v2f IN) : SV_Target
             {
                 half4 color = (tex2D(_MainTex, IN.texcoord) + _TextureSampleAdd) * IN.color;

                 #ifdef UNITY_UI_CLIP_RECT
                 color.a *= UnityGet2DClipping(IN.worldPosition.xy, _ClipRect);
                 #endif

                 #ifdef UNITY_UI_ALPHACLIP
                 clip (color.a - 0.001);
                 #endif

                 return color;
             }
         ENDCG
         }
     }
 }

1.模板测试

2.

UnityGet2DClipping的定义在UnityUI.cginc中：

 inline float UnityGet2DClipping (in float2 position, in float4 clipRect)
 {
     float2 inside = step(clipRect.xy, position.xy) * step(position.xy, clipRect.zw);
     return inside.x * inside.y;
 }

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