/*
 * Copyright (c) Contributors to the Open 3D Engine Project.
 * For complete copyright and license terms please see the LICENSE at the root of this distribution.
 *
 * SPDX-License-Identifier: Apache-2.0 OR MIT
 *
 */

// Gaussian Kernel Radius 9, Sigma 1.8
static const uint GaussianKernelSize = 19;
static const int2  TexelOffsetsV[GaussianKernelSize] = {{0, -9}, {0, -8}, {0, -7}, {0, -6}, {0, -5}, {0, -4}, {0, -3}, {0, -2}, {0, -1}, {0, 0}, {0, 1}, {0, 2}, {0, 3}, {0, 4}, {0, 5}, {0, 6}, {0, 7}, {0, 8}, {0, 9}};
static const int2  TexelOffsetsH[GaussianKernelSize] = {{-9, 0}, {-8, 0}, {-7, 0}, {-6, 0}, {-5, 0}, {-4, 0}, {-3, 0}, {-2, 0}, {-1, 0}, {0, 0}, {1, 0}, {2, 0}, {3, 0}, {4, 0}, {5, 0}, {6, 0}, {7, 0}, {8, 0}, {9, 0}};
static const float TexelWeights[GaussianKernelSize] = {
    0.0000011022801820635918f,
    0.000014295732881160677f,
    0.0001370168487067367f,
    0.0009708086495991633f,
    0.005086391900047703f,
    0.019711193240183777f,
    0.056512463228943335f,
    0.11989501853796679f,
    0.18826323520204147f,
    0.21881694875889543f,
    0.18826323520204147f,
    0.11989501853796679f,
    0.056512463228943335f,
    0.019711193240183777f,
    0.005086391900047703f,
    0.0009708086495991633f,
    0.0001370168487067367f,
    0.000014295732881160677f,
    0.0000011022801820635918f
};

float3 GaussianFilter(uint2 screenCoords, int2 texelOffsets[GaussianKernelSize], RWTexture2D<float4> inputImage)
{
    float3 result = float3(0.0f, 0.0f, 0.0f);

    [unroll]
    for (uint i = 0; i < GaussianKernelSize; ++i)
    {
        result += inputImage[screenCoords + texelOffsets[i]].rgb * TexelWeights[i];
    }

    return result;
}