juce_LogRampedValue.h

/*
  ==============================================================================
 
   This file is part of the JUCE library.
   Copyright (c) 2022 - Raw Material Software Limited
 
   JUCE is an open source library subject to commercial or open-source
   licensing.
 
   By using JUCE, you agree to the terms of both the JUCE 7 End-User License
   Agreement and JUCE Privacy Policy.
 
   End User License Agreement: www.juce.com/juce-7-licence
   Privacy Policy: www.juce.com/juce-privacy-policy
 
   Or: You may also use this code under the terms of the GPL v3 (see
   www.gnu.org/licenses).
 
   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.
 
  ==============================================================================
*/
 
namespace juce::dsp
{
 
//==============================================================================
template <typename FloatType>
class LogRampedValue   : public SmoothedValueBase <LogRampedValue <FloatType>>
{
public:
    //==============================================================================
    LogRampedValue() = default;

    LogRampedValue (FloatType initialValue) noexcept
    {
        // Visual Studio can't handle base class initialisation with CRTP
        this->currentValue = initialValue;
        this->target = initialValue;
    }
 
    //==============================================================================
    void setLogParameters (FloatType midPointAmplitudedB, bool rateOfChangeShouldIncrease) noexcept
    {
        jassert (midPointAmplitudedB < (FloatType) 0.0);
        B = Decibels::decibelsToGain (midPointAmplitudedB);
 
        increasingRateOfChange = rateOfChangeShouldIncrease;
    }
 
    //==============================================================================
    void reset (double sampleRate, double rampLengthInSeconds) noexcept
    {
        jassert (sampleRate > 0 && rampLengthInSeconds >= 0);
        reset ((int) std::floor (rampLengthInSeconds * sampleRate));
    }

    void reset (int numSteps) noexcept
    {
        stepsToTarget = numSteps;
 
        this->setCurrentAndTargetValue (this->target);
 
        updateRampParameters();
    }
 
    //==============================================================================
    void setTargetValue (FloatType newValue) noexcept
    {
        if (approximatelyEqual (newValue, this->target))
            return;
 
        if (stepsToTarget <= 0)
        {
            this->setCurrentAndTargetValue (newValue);
            return;
        }
 
        this->target = newValue;
        this->countdown = stepsToTarget;
        source = this->currentValue;
 
        updateRampParameters();
    }
 
    //==============================================================================
    FloatType getNextValue() noexcept
    {
        if (! this->isSmoothing())
            return this->target;
 
        --(this->countdown);
 
        temp *= r; temp += d;
        this->currentValue = jmap (temp, source, this->target);
 
        return this->currentValue;
    }
 
    //==============================================================================
    FloatType skip (int numSamples) noexcept
    {
        if (numSamples >= this->countdown)
        {
            this->setCurrentAndTargetValue (this->target);
            return this->target;
        }
 
        this->countdown -= numSamples;
 
        auto rN = (FloatType) std::pow (r, numSamples);
        temp *= rN;
        temp += d * (rN - (FloatType) 1) / (r - (FloatType) 1);
 
        this->currentValue = jmap (temp, source, this->target);
        return this->currentValue;
    }
 
private:
    //==============================================================================
    void updateRampParameters()
    {
        auto D = increasingRateOfChange ? B : (FloatType) 1 - B;
        auto base = ((FloatType) 1 / D) - (FloatType) 1;
        r = std::pow (base, (FloatType) 2 / (FloatType) stepsToTarget);
        auto rN = std::pow (r, (FloatType) stepsToTarget);
        d = (r - (FloatType) 1) / (rN - (FloatType) 1);
        temp = 0;
    }
 
    //==============================================================================
    bool increasingRateOfChange = true;
    FloatType B = Decibels::decibelsToGain ((FloatType) -40);
 
    int stepsToTarget = 0;
    FloatType temp = 0, source = 0, r = 0, d = 1;
};
 
} // namespace juce::dsp