// Emissive-Gloam — the LANTERN "true vs false light" master shader.
// One shader is the whole palette rule: hue = warm(ours)/cold(gloam)/lure; and the
// load-bearing readability channel is CADENCE — _FlickerAmount 0 = STEADY (true light),
// >0 = guttering FALSE light. Flicker lives in-shader (uses _Time), so it needs no script
// and reads in edit + play. HDR emission so URP Bloom catches it. Unlit: these are glows.
Shader "ProjectM/EmissiveGloam"
{
    Properties
    {
        [HDR] _EmissionColor ("Emission (HDR)", Color) = (0.1, 0.8, 0.5, 1)
        _FlickerAmount ("Flicker Amount (0=steady/true, 1=false)", Range(0,1)) = 0.0
        _FlickerSpeed ("Flicker Speed", Float) = 6.0
        _Seed ("Per-material phase seed", Float) = 0.0
    }
    SubShader
    {
        Tags { "RenderType"="Opaque" "RenderPipeline"="UniversalPipeline" "Queue"="Geometry" }
        Pass
        {
            Name "EmissiveGloamUnlit"
            Tags { "LightMode"="UniversalForward" }
            HLSLPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"

            struct Attributes { float4 positionOS : POSITION; };
            struct Varyings   { float4 positionHCS : SV_POSITION; };

            CBUFFER_START(UnityPerMaterial)
                half4 _EmissionColor;
                half  _FlickerAmount;
                half  _FlickerSpeed;
                half  _Seed;
            CBUFFER_END

            Varyings vert (Attributes IN)
            {
                Varyings OUT;
                OUT.positionHCS = TransformObjectToHClip(IN.positionOS.xyz);
                return OUT;
            }

            half4 frag (Varyings IN) : SV_Target
            {
                float t = _Time.y * _FlickerSpeed + _Seed;
                // layered sines -> an organic guttering wave in [-1,1]
                float wave = 0.6 * sin(t) + 0.4 * sin(t * 2.37 + 1.3);
                // f = 1 when steady (_FlickerAmount==0); dips toward (1-_FlickerAmount) as it gutters
                float f = 1.0 - _FlickerAmount * (0.5 - 0.5 * wave);
                return half4(_EmissionColor.rgb * f, 1.0);
            }
            ENDHLSL
        }
    }
    Fallback Off
}