WakeSampleParts.h

#pragma once
 
#include <marenv/marenv.h>
#include <marenv/wake/WakeTypes.h>
 
namespace marenv::wake
{
inline double BlendWeight(double t, double start, double time)
{
    if (!(time > 0.0))
        return 1.0;
    const double tau = (t - start) / time;
    if (tau <= 0.0)
        return 0.0;
    if (tau >= 1.0)
        return 1.0;
    return tau * tau * (3.0 - 2.0 * tau);
}
 
struct WakeBlendSum
{
    bool inside                = false; 
    double deficit             = 0.0; 
    double weightedVelocity[3] = {0.0, 0.0, 0.0}; 
 
    void Add(double share, const WakeSample& sample)
    {
        inside = true;
        deficit += share * sample.deficit;
        for (int i = 0; i < 3; ++i)
            weightedVelocity[i] += share * sample.deficit * sample.sourceVelocity[i];
    }
 
    void Add(double share, const WakeBlendSum& part)
    {
        inside = true;
        deficit += share * part.deficit;
        for (int i = 0; i < 3; ++i)
            weightedVelocity[i] += share * part.weightedVelocity[i];
    }
 
    Status ToSample(const double zeroDeficitVelocity[3], WakeSample& out) const
    {
        if (!inside) {
            out = WakeSample {0.0, {0.0, 0.0, 0.0}};
            return Status::ERROR_NOT_SET;
        }
        out.deficit = deficit;
        for (int i = 0; i < 3; ++i)
            out.sourceVelocity[i] = deficit > 0.0 ? weightedVelocity[i] / deficit : zeroDeficitVelocity[i];
        return Status::OK;
    }
};
 
struct WakeBlendSamples
{
    bool currentInside = false; 
    WakeSample current {}; 
    WakeBlendSum previous {}; 
    double start = 0.0; 
    double time  = 0.0; 
 
    WakeBlendSum At(double t) const
    {
        WakeBlendSum sum;
        const double weight = BlendWeight(t, start, time);
        if (weight > 0.0 && currentInside)
            sum.Add(weight, current);
        if (weight < 1.0 && previous.inside)
            sum.Add(1.0 - weight, previous);
        return sum;
    }
};
 
struct WakeSampleParts
{
    bool blending = false; 
    Status status = Status::ERROR_NOT_SET; 
    WakeSample sample {}; 
    WakeBlendSamples blend {}; 
    double zeroDeficitVelocity[3] = {0.0, 0.0, 0.0}; 
 
    Status At(double t, WakeSample& out) const
    {
        if (!blending) {
            out = sample;
            return status;
        }
        return blend.At(t).ToSample(zeroDeficitVelocity, out);
    }
};
} // namespace marenv::wake