// BVLE Voxels - AO Apply + Tone Mapping Compute Shader (Phase 6.3 + 7)
// Final post-process pass: applies AO, saturation boost, and tone mapping.

#include "voxelCommon.hlsli"

Texture2D<float> aoBlurred : register(t0);
RWTexture2D<float4> colorOutput : register(u0);

struct ApplyPush {
    uint width;
    uint height;
    uint debugMode; // 0=normal, 2=debug AO (show AO as grayscale)
    uint pad[9];
};
[[vk::push_constant]] ConstantBuffer<ApplyPush> push : register(b999);

// Soft clamp tone mapping: linear up to shoulder, gentle roll-off to prevent harsh clipping
float3 softClampToneMap(float3 color, float exposure) {
    color *= exposure;
    // Soft exponential curve: gentler than Reinhard, preserves bright midtones
    return 1.0 - exp(-color);  // natural 1-e^-x curve
}

// Saturation adjustment in linear space
float3 adjustSaturation(float3 color, float saturation) {
    float luma = dot(color, float3(0.2126, 0.7152, 0.0722));
    return lerp(float3(luma, luma, luma), color, saturation);
}

[RootSignature(VOXEL_ROOTSIG)]
[numthreads(8, 8, 1)]
void main(uint3 DTid : SV_DispatchThreadID) {
    if (DTid.x >= push.width || DTid.y >= push.height) return;

    float ao = aoBlurred[DTid.xy];

    if (push.debugMode == 2) {
        // Debug AO: grayscale visualization of blurred AO
        colorOutput[DTid.xy] = float4(ao, ao, ao, 1);
    } else {
        float4 color = colorOutput[DTid.xy];

        // Apply AO
        color.rgb *= ao;

        // Saturation boost (toneMapParams.x)
        color.rgb = adjustSaturation(color.rgb, toneMapParams.x);

        // Tone mapping (toneMapParams.y = exposure)
        color.rgb = softClampToneMap(color.rgb, toneMapParams.y);

        colorOutput[DTid.xy] = color;
    }
}