/*
 * 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
 *
 */

inline float InvertDepth(float depth)
{
    // Convert depth from [1.0 - 0.0] to [0.0 - 1.0].
    // Set the front(near side) to 0.0 and the back(far side) to 1.0.

    return 1.0f - depth;
}

inline float4 InvertDepth(float4 depth)
{
    // Convert depth from [1.0 - 0.0] to [0.0 - 1.0].
    // Set the front(near side) to 0.0 and the back(far side) to 1.0.

    return float4(1, 1, 1, 1) - depth;
}

inline float ConvertDofFactor(float depth, float far, float near, float focusDistance)
{
    // dofFactor : The value Calculated from depth.
    //             This is used to calculate blend ratio from dofFactor when combining buffers.
    // dofFactor = (z-L)/z
    //           = ((far-near)*L/far*near) * depth + (1-L/near)
    //           = cameraFactor.x * depth + cameraFactor.y
    // L : target object distance.
    // z : camera (depthLinear)
    //     z = -far*near / (far*depth - near*depth - far) [from (depth[0-1] = (far*(z-near)/(far-near)/z))]

    float z = -far*near / (far*depth - near*depth - far);
    float dofFactor = (z - focusDistance) / z;

    return dofFactor;
}

inline float ConvertBlend(float dofFactor, float2 blendFactor)
{
    return dofFactor * blendFactor.x + blendFactor.y;
}

inline float4 ConvertBlendsFloat4(float4 dofFactors, float2 blendFactor)
{
    return dofFactors * blendFactor.x + blendFactor.y;
}