// 魔法光晕 Shader（叠加发光）
// 挂在比光球稍大的 Sphere 上，Additive 叠加，模拟没有 Bloom 也能发光的光晕
Shader "Custom/MagicGlow"
{
    Properties
    {
        _GlowColor ("光晕颜色", Color) = (1.0, 0.5, 0.2, 0.6)
        _GlowPower("光晕强度", Range(0.5, 5.0)) = 2.0
    }
    SubShader
    {
        Tags { "RenderType"="Transparent" "Queue"="Transparent" "IgnoreProjector"="True" }
        LOD 100
        ZWrite Off
        Cull Off
        Blend SrcAlpha One   // Additive 叠加，越叠越亮

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"

            struct appdata
            {
                float4 vertex : POSITION;
                float3 normal : NORMAL;
            };

            struct v2f
            {
                float4 vertex : SV_POSITION;
                float3 worldNormal : TEXCOORD0;
                float3 worldViewDir : TEXCOORD1;
            };

            float4 _GlowColor;
            float  _GlowPower;

            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.worldNormal  = UnityObjectToWorldNormal(v.normal);
                o.worldViewDir = normalize(WorldSpaceViewDir(v.vertex));
                return o;
            }

            fixed4 frag (v2f i) : SV_Target
            {
                float3 n = normalize(i.worldNormal);
                float3 v = normalize(i.worldViewDir);
                // 边缘亮、中心透明 → 柔和半球光晕
                float rim = pow(1.0 - saturate(dot(n, v)), _GlowPower);
                return float4(_GlowColor.rgb, rim * _GlowColor.a);
            }
            ENDCG
        }
    }
}