Shader "Chameleon/Laser"
{
    // Unlit additive beam for the hunter's shot LineRenderer. The animated fade (opacity) is carried by the
    // per-vertex colour alpha the HunterLaserBeam writes each frame; _Color is the constant HDR tint.
    Properties
    {
        [HDR] _Color ("Color", Color) = (1, 0.25, 0.18, 1)
        _Softness ("Edge Softness", Range(0, 1)) = 1
    }

    SubShader
    {
        Tags { "RenderType" = "Transparent" "Queue" = "Transparent" "RenderPipeline" = "UniversalPipeline" "IgnoreProjector" = "True" }

        Pass
        {
            Name "LaserAdditive"
            Blend One One   // pure additive glow (vertex-alpha folded into rgb below)
            ZWrite Off
            Cull Off
            ZTest LEqual    // the beam is occluded by nearer opaque geometry

            HLSLPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"

            struct Attributes
            {
                float4 positionOS : POSITION;
                float4 color      : COLOR;
                float2 uv         : TEXCOORD0;
            };

            struct Varyings
            {
                float4 positionHCS : SV_POSITION;
                float4 color       : COLOR;
                float2 uv          : TEXCOORD0;
            };

            half4 _Color;
            half  _Softness;

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

            half4 frag (Varyings IN) : SV_Target
            {
                // LineRenderer maps UV.y across the strip width (0..1): bright core, soft edges.
                half across = abs(IN.uv.y * 2.0h - 1.0h);
                half edge = lerp(1.0h, saturate(1.0h - across), saturate(_Softness));
                half intensity = IN.color.a * edge;                 // vertex alpha = animated fade envelope
                half3 rgb = _Color.rgb * IN.color.rgb * intensity;
                return half4(rgb, 1.0h);                            // additive (Blend One One) -> alpha unused
            }
            ENDHLSL
        }
    }
    Fallback Off
}