shader学习记录—圆环进度条

Shader "Custom/ShaderToy/进度条"
{
    Properties
    {
        _MainTex("Texture", 2D) = "white" {}
        _Progress("Progress",float) =0.1
    }
        SubShader
    {
        Tags { "RenderType" = "Opaque" }
        LOD 100

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            // make fog work
            #pragma multi_compile_fog

            #include "UnityCG.cginc"

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

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

            sampler2D _MainTex;
            float4 _MainTex_ST;
            float _Progress;

            v2f vert(appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = TRANSFORM_TEX(v.uv, _MainTex);
                UNITY_TRANSFER_FOG(o,o.vertex);
                return o;
            }
             
            
            fixed4 frag(v2f i) : SV_Target
            {
             float pi = 3.1415926;
             float2 uv = i.uv - float2(0.5,0.5);
            //画圆环
            float d =step(0.4,length(uv));
            d+=1-step(0.35,length(uv));
            //设置起点
            float angle = (atan2(uv.y, uv.x))+ pi *0.5;
            if (angle < 0.0) angle += pi * 2.0;
            //控制进度
            d += step(_Progress,angle);
            float4 col = float4(1, d, d, 1);
            return col;
            }
            ENDCG
        }
    }
}