// 魔法光球本体 Shader
// 挂在小球 Sphere 上：自发光、脉动、边缘 Fresnel 光，模拟能量球
Shader "Custom/MagicOrb"
{
    Properties
    {
        _OrbColor  ("光球颜色", Color) = (1.0, 0.35, 0.1, 1.0)   // 默认火球橙红
        _CoreColor ("核心颜色", Color) = (1.0, 0.95, 0.7, 1.0)  // 核心亮黄白
        _PulseSpeed("脉动速度", Range(0.5, 5.0)) = 2.0
        _RimPower  ("边缘光强度", Range(0.5, 5.0)) = 2.0
    }
    SubShader
    {
        Tags { "RenderType"="Opaque" "Queue"="Geometry" }
        LOD 100
        Cull Off

        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 _OrbColor;
            float4 _CoreColor;
            float  _PulseSpeed;
            float  _RimPower;

            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);
                float  ndv = saturate(dot(n, v));

                // 边缘光（Fresnel）：球的轮廓一圈更亮
                float rim = pow(1.0 - ndv, _RimPower);
                // 脉动：呼吸感
                float pulse = 0.82 + 0.18 * sin(_Time.y * _PulseSpeed * 3.14159);
                // 核心（朝向镜头的部分）偏亮白
                float3 col = lerp(_OrbColor.rgb, _CoreColor.rgb, ndv * 0.65);
                col += rim * _OrbColor.rgb * 1.5;
                col *= pulse;

                return float4(col, 1.0);
            }
            ENDCG
        }
    }
}