Loading效果之一Shader

代碼如下：

Shader "Hidden/Loading_01"
{
    Properties
    {
		_Color("Color", Color) = (1, 1, 1, 1)
        _Radius ("Radius", Range(0, 0.5)) = 0.1
		_Width("Width", Range(0, 0.5)) = 0.1
		_Breath ("Breath", float) = 1
		_Num ("Num", int) = 1
		_Dir ("Dir", int) = 1
    }
    SubShader
    {
		Blend SrcAlpha OneMinusSrcAlpha

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

            struct appdata
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
            };

            struct v2f
            {
                float2 uv : TEXCOORD0;
                float4 vertex : SV_POSITION;
            };

            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = v.uv;
                return o;
            }

			fixed4 _Color;

			fixed _Radius;

			fixed _Width;

			fixed _Breath;

			fixed _Dir;

			int _Num;

			fixed drawRing(fixed rMax, fixed rMin, fixed2 uv)
			{
				fixed r = sqrt(uv.x * uv.x + uv.y * uv.y);

				return step(rMin, r) * step(r, rMax);
			}
            
			fixed getZeroToOneLoop()
			{
				return fmod(_Time.y * _Breath, 1);
			}

			fixed4 frag (v2f i) : SV_Target
            {
                fixed2 newUv = i.uv - fixed2(0.5, 0.5);
				
				float angle = 360.0 / _Num;
				
				fixed curAngle = degrees(atan2(newUv.y, newUv.x)) + 180;
				
				int interval = curAngle / angle;
				
				int odd = fmod(interval, 2);
				
				interval += step(_Dir, 0) *_Num + _Dir * _Num * getZeroToOneLoop();

				interval = fmod(interval, _Num);

				_Color.a = odd * drawRing(_Radius +_Width, _Radius, newUv) * interval / _Num;
				
				return _Color;
            }
            ENDCG
        }
    }
}