Unity Shader 扇形进度条

我们知道在Unity后面的版本中SpriteRenderer已经有了Tiled功能，可以实现扇形进度条的功能，不过如果我们需要多种样式的进度条，可能就需要写shader了。下面是实现扇形进度条的代码，如果需要其他样式 的，可以直接修改。

Shader "My/Pie" {
Properties {
    _MainTex ("Base (RGB) Trans (A)", 2D) = "white" {}
    _Angle("Pie Angle",Range(0,360)) = 360
}

SubShader {
    Tags {"Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent"}
    LOD 100

    ZWrite Off
    Blend SrcAlpha OneMinusSrcAlpha

    Pass {
        CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #pragma target 2.0
            #pragma multi_compile_fog

            #include "UnityCG.cginc"

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

            struct v2f {
                float4 vertex : SV_POSITION;
                float2 texcoord : TEXCOORD0;
                UNITY_FOG_COORDS(1)
                UNITY_VERTEX_OUTPUT_STEREO
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;

            v2f vert (appdata_t v)
            {
                v2f o;
                UNITY_SETUP_INSTANCE_ID(v);
                UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(o);
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.texcoord = TRANSFORM_TEX(v.texcoord, _MainTex);
                UNITY_TRANSFER_FOG(o,o.vertex);
                return o;
            }
            
            half _Angle;
            fixed _Gradient;

            fixed4 frag (v2f i) : SV_Target
            {
                fixed4 col = tex2D(_MainTex, i.texcoord);
                
                half2 cuv = i.texcoord - half2(0.5,0.5);
                half2 luv = half2(1,0);
                
                half2 s = cuv.x * luv.y - luv.x * cuv.y;  
                half2 c = cuv.x * luv.x + cuv.y * luv.y;
                
                half2 angle = atan2(s, c) * (180 / 3.1416);
                
                angle += step(0,cuv.y)*360;
                
                clip(angle-_Angle);
                                                
                UNITY_APPLY_FOG(i.fogCoord, col);
                return col;
            }
        ENDCG
    }
}

}