Unity使用Shader快速制作一个圆形遮罩

最近看到橙子做了一个类似于音乐播放器的功能。感觉挺不错的，特地拿出来分享给大家。

在这里插入图片描述

点击播放以后中间的圆型图片会开始转动，用过某易音乐的或者其他手机播放器的都懂。然后因为我（懒）不想去把一个一个图片再去切成圆型，所以就想用Shader来做一下遮罩。

提示：以下是本篇文章正文内容，下面案例可供参考

一、创建Shader

首先新建一个文件夹，起名为：Shaders

在这里插入图片描述

起名为UICircular 双击打开把下面代码复制进去

//By:橙子 2022-5-11 唯一博客地址：https://blog.csdn.net/weixin_45375968
Shader "Custom/UICircular"
{
	Properties
	{
		_R("圆的半径R", Range(0,1)) = 0.5
		_Blur("边缘虚化的范围", Range(0,100)) = 100

		[PerRendererData] _MainTex("Sprite Texture", 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
			{
				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
				};

				fixed4 _Color;
				fixed4 _TextureSampleAdd;
				float4 _ClipRect;
				float _R;
				float _X;
				float _Y;
				float _Blur;

				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 = v.texcoord;

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

				sampler2D _MainTex;

				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

					//圆形
					float x = IN.texcoord.x - 0.5f;
					float y = IN.texcoord.y - 0.5f;
					float lerp = (1 - _Blur * (_R * _R - (x * x + y * y))) * color.a;//如果不加这句代码，图片边缘会有明显的锯齿
					color.a = (color.a - lerp) * step(x * x + y * y, _R * _R);//如果 _R*_R<(x*x + y * y)，返回 0；否则，返回 1。

					return color;
				}
			ENDCG
			}
		}
}