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/*
* Copyright (c) 2008-2017, NVIDIA CORPORATION. All rights reserved.
*
* NVIDIA CORPORATION and its licensors retain all intellectual property
* and proprietary rights in and to this software, related documentation
* and any modifications thereto. Any use, reproduction, disclosure or
* distribution of this software and related documentation without an express
* license agreement from NVIDIA CORPORATION is strictly prohibited.
*/
#include "Apex.h"
#include "variable_oscillator.h"
#include "PxMath.h"
namespace nvidia
{
namespace apex
{
variableOscillator::variableOscillator(float min, float max, float initial, float period) :
mMin(min),
mMax(max),
mPeriod(period),
mStartVal(initial),
mLastVal(initial)
{
mCumTime = 0.0f;
mGoingUp = true;
mEndVal = computeEndVal(mMin, mMax);
}
variableOscillator::~variableOscillator()
{
}
float variableOscillator::computeEndVal(float current, float maxOrMin)
{
float target;
float maxDelta;
float quarterVal;
// compute the max range of the oscillator
maxDelta = maxOrMin - current;
// find the 'lower bound' of the oscillator peak
quarterVal = current + (maxDelta / 4.0f);
// get a rand between 0 and 1
target = (float) ::rand() / (float) RAND_MAX;
// scale the rand to the range we want
target = target * PxAbs(quarterVal - maxOrMin);
// add the offset to the scaled random number.
if (current < maxOrMin)
{
target = target + quarterVal;
}
else
{
target = quarterVal - target;
}
return(target);
}
float variableOscillator::updateVariableOscillator(float deltaTime)
{
float returnVal;
float halfRange;
mCumTime += deltaTime;
// has the function crossed a max or a min?
if ((mGoingUp && (mCumTime > (mPeriod / 2.0f))) ||
(!mGoingUp && (mCumTime > mPeriod)))
{
mStartVal = mLastVal;
if (mGoingUp)
{
mEndVal = computeEndVal(mStartVal, mMin);
}
else
{
mEndVal = computeEndVal(mStartVal, mMax);
mCumTime = mCumTime - mPeriod;
}
mGoingUp = !mGoingUp;
}
halfRange = 0.5f * PxAbs(mEndVal - mStartVal);
returnVal = -halfRange * PxCos(mCumTime * PxTwoPi / mPeriod) + halfRange + PxMin(mStartVal, mEndVal);
mLastVal = returnVal;
return(returnVal);
}
}
} // namespace nvidia::apex
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