cxTrackingPositionFilter.cpp

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/*=========================================================================
This file is part of CustusX, an Image Guided Therapy Application.

Copyright (c) 2008-2014, SINTEF Department of Medical Technology
All rights reserved.

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modification, are permitted provided that the following conditions are met:

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   this list of conditions and the following disclaimer.

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   and/or other materials provided with the distribution.

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   may be used to endorse or promote products derived from this software 
   without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
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=========================================================================*/
#include "cxTrackingPositionFilter.h"
#include "iir/Butterworth.h"

namespace cx
{

TrackingPositionFilter::TrackingPositionFilter()
{
        mCutOffFrequency = 3;
        mResampleFrequency = 100;
        this->reset();
}

void TrackingPositionFilter::setCutOffFrequency(double freq)
{
        mCutOffFrequency = freq;
        this->reset();
}

void TrackingPositionFilter::addPosition(Transform3D pos, double timestamp)
{
        this->clearIfTimestampIsOlderThanHead(pos, timestamp);
        this->clearIfJumpInTimestamps(pos, timestamp);

        if (mResampled.empty())
        {
                mResampled[timestamp] = pos;
                mHistory[timestamp] = pos;
                return;
        }

        this->interpolateAndFilterPositions(pos, timestamp);
        mHistory[timestamp] = pos;
}

Transform3D TrackingPositionFilter::getFilteredPosition()
{
        if (mFiltered.size() > mResampleFrequency) //check if mFiltered contains enough positions for the filter to be stable
                return mFiltered.rbegin()->second;
        else if (!mHistory.empty())
                return mHistory.rbegin()->second;
        else
                return Transform3D::Identity();
}

void TrackingPositionFilter::clearIfTimestampIsOlderThanHead(Transform3D pos, double timestamp)
{
        if (mResampled.empty())
                return;

        if (timestamp < mResampled.rbegin()->first)
        {
                // clear history if old timestamps appear
                this->reset();
        }
}

void TrackingPositionFilter::clearIfJumpInTimestamps(Transform3D pos, double timestamp)
{
        if (mResampled.empty())
                return;

        double timeStep = timestamp - mResampled.rbegin()->first;
        if ( timeStep > 1000)
        {
                // clear history of resampled and filtered data if jump in timestamps of more than 1 second
                this->reset();
        }
}

void TrackingPositionFilter::interpolateAndFilterPositions(Transform3D pos, double timestamp)
{
        Transform3D previousPositionMatrix = mHistory.rbegin()->second;
        double deltaT = timestamp - mHistory.rbegin()->first; //time from previous measured position to this position
        int numberOfInterpolationPoints = floor( (timestamp - mResampled.rbegin()->first)/1000 * mResampleFrequency ); // interpolate from last resampled position to current measured position
        Transform3D interpolatedPosition;
        Transform3D filteredPosition;
        for (int i=0; i < numberOfInterpolationPoints; i++)
        {
                double resampledTimestamp = mResampled.rbegin()->first + 1000/mResampleFrequency;
                double deltaTpast = resampledTimestamp - mHistory.rbegin()->first;
                double deltaTfuture = timestamp - resampledTimestamp;
                interpolatedPosition = pos.matrix() * deltaTpast/deltaT + previousPositionMatrix.matrix() * deltaTfuture/deltaT; // linear interpolation between previous and current measured position
                mResampled[resampledTimestamp] = interpolatedPosition;

                filteredPosition = interpolatedPosition;
                filteredPosition(0,3) = fx.filter(interpolatedPosition(0,3));
                filteredPosition(1,3) = fy.filter(interpolatedPosition(1,3));
                filteredPosition(2,3) = fz.filter(interpolatedPosition(2,3));
                mFiltered[resampledTimestamp] = filteredPosition;
        }
}

void TrackingPositionFilter::reset()
{
        mHistory.clear();
        mResampled.clear();
        mFiltered.clear();

        fx.setup (mFilterOrder, mResampleFrequency, mCutOffFrequency);  // Lag perker isteden
        fx.reset ();
        fy.setup (mFilterOrder, mResampleFrequency, mCutOffFrequency);
        fy.reset ();
        fz.setup (mFilterOrder, mResampleFrequency, mCutOffFrequency);
        fz.reset ();
}


} // namespace cx