노이즈 텍스처와 스텝 함수 기반 URP 디졸브(Dissolve) 번 엣지 셰이더

Shader "Custom/URP/DissolveBurn"
{
    Properties
    {
        _BaseMap ("Texture", 2D) = "white" {}
        _BaseColor ("Color", Color) = (1,1,1,1)
        _NoiseMap ("Noise Map", 2D) = "white" {}
        _Cutoff ("Dissolve Amount", Range(0, 1)) = 0.0
        _EdgeWidth ("Edge Width", Range(0, 0.2)) = 0.05
        [HDR] _EdgeColor ("Edge Burn Color", Color) = (2, 0.5, 0, 1)
    }
    SubShader
    {
        Tags { "RenderType" = "Opaque" "RenderPipeline" = "UniversalPipeline" }
        Pass
        {
            Name "ForwardLit"
            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;
                float2 uv : TEXCOORD0;
            };

            struct Varyings
            {
                float4 positionCS : SV_POSITION;
                float2 uv : TEXCOORD0;
            };

            TEXTURE2D(_BaseMap);   SAMPLER(sampler_BaseMap);
            TEXTURE2D(_NoiseMap);  SAMPLER(sampler_NoiseMap);

            CBUFFER_START(UnityPerMaterial)
                float4 _BaseMap_ST;
                float4 _NoiseMap_ST;
                half4 _BaseColor;
                half4 _EdgeColor;
                float _Cutoff;
                float _EdgeWidth;
            CBUFFER_END

            Varyings vert(Attributes input)
            {
                Varyings output;
                output.positionCS = TransformObjectToHClip(input.positionOS.xyz);
                output.uv = TRANSFORM_TEX(input.uv, _BaseMap);
                return output;
            }

            half4 frag(Varyings input) : SV_Target
            {
                half noise = SAMPLE_TEXTURE2D(_NoiseMap, sampler_NoiseMap, input.uv).r;
                clip(noise - _Cutoff); // 컷오프보다 작으면 픽셀 폐기

                half4 baseTex = SAMPLE_TEXTURE2D(_BaseMap, sampler_BaseMap, input.uv) * _BaseColor;
                // 가장자리 영역 마스킹 (noise가 _Cutoff + _EdgeWidth 미만일 때)
                float edgeFactor = 1.0 - saturate((noise - _Cutoff) / max(_EdgeWidth, 0.0001));
                half3 finalColor = lerp(baseTex.rgb, _EdgeColor.rgb, edgeFactor);

                return half4(finalColor, baseTex.a);
            }
            ENDHLSL
        }
    }
}