// Each #kernel tells which function to compile; you can have many kernels
#pragma kernel Paint
#include "../Includes/GPUNoiseParams.cginc"
#include "../Includes/GPUNoise.cginc"

Texture2D<float> _InputDisplacement;
Texture2D<float> _InputBrushTexture;
RWTexture2D<float> _OutputDisplacement;

int _EffectType = 0; // Raise = 0, Lower = 1, Flatten = 2, ClearTrees = 3, ClearDetails = 4, Texture = 5, Detail = 6
float _PaintStrength;
float _FlattenHeight = 0.0f;
float _wResolution = 1000.0f;
float2 _iResolution = 513.0f;
float2 _Offset = 0.0f;

float MoveTowards(float current, float target, float maxDelta)
{
    if (abs(target - current) <= maxDelta)
        return target;
    return current + sign(target - current) * maxDelta;
}

[numthreads(16,16,1)]
void Paint(uint3 id : SV_DispatchThreadID)
{
    const uint2 coord = id.xy;
    //---------------
    float height = _InputDisplacement[coord];
    float brush = _InputBrushTexture[coord] * 2.0f;
    // const uint2 mid = _iResolution.xy / 2;
    // float2 center = ((float2)mid + _Offset) / _iResolution.xy;
    // float2 coordinate = ((float2)coord + _Offset) / _iResolution.xy;
    // const float xRes = _iResolution.x;
    // const float yRes = _iResolution.y;
    // float xPos = coordinate.x * xRes;
    // float yPos = coordinate.y * yRes;
    // const float2 worldPos = float2(xPos, yPos);

    float2 coordinate = (float2)id.xy + _Offset;
    // calculate the subpixel offset (to compensate for 257x257 vs 256x256 thing).
    float2 offset = coordinate * (float2(1.0f, 1.0f) / _iResolution.xy);
    coordinate += offset;
    coordinate /= _iResolution.xy;
    float xRes = coordinate.x * _wResolution;
    float yRes = coordinate.y * _wResolution;
    const float2 worldPos = float3(xRes, 0.f, yRes);

    // if (_NoisemapEnabled)
    // {
    //     const float distance = length(center.xy - coordinate.xy);
    //     const float falloff = EvaluateFalloff(distance, _NoiseFalloff, _NoiseFalloffCount);
    //     const float noise = GetNoise(worldPos) * falloff * _NoisemapStrength;
    //     brush *= 1.0f + noise;
    // }
    
    const float displacement = brush * _PaintStrength;
    switch (_EffectType)
    {
    case 0: // Raise
        height += displacement;
        break;
    case 1: // Lower
        height -= displacement;
        break;
    case 2: // Flatten
        //height = MoveTowards(height, flattenHeight * .5f, brush * strength);
        const float delta = clamp(displacement, 0.f, 1.f);
        height = lerp(height, _FlattenHeight * .5f, delta);
        break;
    case 3: // Clear Trees
    case 4: // Clear Details
    case 5: // Texture
    case 6: // Details
        height = displacement;
        break;
    default:
        break;
    }
    _OutputDisplacement[coord] = height;
}