Shader "Custom/HDRtoSDR" {
	Properties{
		_MainTex("Texture", 2D) = "white" {}
	}
		SubShader{
			Tags { "RenderType" = "Opaque" }
			LOD 100

			Pass {
				CGPROGRAM
				#pragma vertex vert
				#pragma fragment frag

				#include "UnityCG.cginc"

				struct appdata {
					float4 vertex : POSITION;
					float2 uv : TEXCOORD0;
				};

				struct v2f {
					float2 uv : TEXCOORD0;
					float4 vertex : SV_POSITION;
				};

				sampler2D _MainTex;
				float4 _MainTex_ST;

				v2f vert(appdata v) {
					v2f o;
					o.vertex = UnityObjectToClipPos(v.vertex);
					o.uv = TRANSFORM_TEX(v.uv, _MainTex);
					return o;
				}

				fixed4 frag(v2f i) : SV_Target {
				
					// Sample the texture
				fixed4 col = tex2D(_MainTex, i.uv);

				// Apply Reinhard Tone Mapping
				col.rgb = col.rgb / (col.rgb + 1.0);

				// Gamma correction (assuming gamma = 2.2)
				col.rgb = pow(col.rgb, 1.0 / 2.2);

				// Premultiply alpha
				col.rgb *= col.a;

				return col;
			}
			ENDCG
		}
	}
}

using System;
using UnityEngine;
using UnityEngine.Rendering.PostProcessing;

[Serializable]
[PostProcess(typeof(HDRToSDRRenderer), PostProcessEvent.AfterStack, "Custom/HDRtoSDR")]
public sealed class HDRToSDR : PostProcessEffectSettings
{
}

public sealed class HDRToSDRRenderer : PostProcessEffectRenderer<HDRToSDR>
{
    public override void Render(PostProcessRenderContext context)
    {
        var sheet = context.propertySheets.Get(Shader.Find("Custom/HDRtoSDR"));
        context.command.BlitFullscreenTriangle(context.source, context.destination, sheet, 0);
    }
}

col.rgb = col.rgb / (col.rgb + 1.0);