[UnityShader效果]01.Mask

参考链接：

https://blog.****.net/akof1314/article/details/50428200

1.Mask.shader

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

 Shader "Custom/Mask"
 {
     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) = 

         _MaskTex ("Mask Texture", 2D) = "white" {}
     }

     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;

             sampler2D _MaskTex;

             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;
                 color.a *= tex2D(_MaskTex, IN.texcoord).a;

                 #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
         }
     }
 }

核心代码：

 color.a *= tex2D(_MaskTex, IN.texcoord).a;

即遮罩图alpha=0的地方不会显示

遮罩图和效果图(遮罩图白色的地方实际上是透明的)：

2.UV问题

上面的结果表面上看是没什么问题的，但如果把图片打进图集就会发现不对了。原因是，shader里面uv坐标不再是单个图片的坐标了，而是图集里面该图片的坐标，使得shader计算错误，最终渲染错乱。解决方法是，将单个图片的纹理坐标保存到uv1中。

SetVertUV1.cs

 using UnityEngine;
 using UnityEngine.UI;

 public class SetVertUV1 : BaseMeshEffect
 {
     public override void ModifyMesh(VertexHelper vh)
     {
         UIVertex uiVertex = new UIVertex();
         for (int i = ; i < vh.currentVertCount; i++)
         {
             vh.PopulateUIVertex(ref uiVertex, i);
             int uvX = i >> ;
             int uvY = uvX ^ (i & );
             uiVertex.uv1 = new Vector2(uvX, uvY);
             vh.SetUIVertex(uiVertex, i);
         }
     }
 }

即将4个顶点的uv1依次设置为(0,0),(0,1),(1,1),(1,0)

MaskUV1.shader

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

 Shader "Custom/MaskUV1"
 {
     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) = 

         _MaskTex ("Mask Texture", 2D) = "white" {}
     }

     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;
                 float2 texcoord1 : TEXCOORD1;
                 UNITY_VERTEX_INPUT_INSTANCE_ID
             };

             struct v2f
             {
                 float4 vertex   : SV_POSITION;
                 fixed4 color    : COLOR;
                 float2 texcoord  : TEXCOORD0;
                 float4 worldPosition : TEXCOORD1;
                 float2 texcoord1 : TEXCOORD2;
                 UNITY_VERTEX_OUTPUT_STEREO
             };

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

             sampler2D _MaskTex;

             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;
                 OUT.texcoord1 = v.texcoord1;
                 return OUT;
             }

             fixed4 frag(v2f IN) : SV_Target
             {
                 half4 color = (tex2D(_MainTex, IN.texcoord) + _TextureSampleAdd) * IN.color;
                 color.a *= tex2D(_MaskTex, IN.texcoord1).a;

                 #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
         }
     }
 }