LinearEase.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreTypes.h"
 
 
class FLinearEase
{
public:
    FLinearEase()
        : StartValue(0.0f)
        , CurrentValue(0.0f)
        , DeltaValue(0.0f)
        , SampleRate(44100.0f)
        , DurationTicks(0)
        , DefaultDurationTicks(0)
        , CurrentTick(0)
    { }
 
    ~FLinearEase() { }
 
    bool IsDone() const
    {
        return CurrentTick >= DurationTicks;
    }
 
    void Init(float InSampleRate)
    {
        SampleRate = InSampleRate;
    }
 
    void SetValueRange(const float Start, const float End, const float InTimeSec)
    {
        StartValue = Start;
        CurrentValue = Start;
        SetValue(End, InTimeSec);
    }
 
    float GetValue()
    {
        if (IsDone())
        {
            return CurrentValue;
        }
 
        CurrentValue = DeltaValue * (float)CurrentTick / DurationTicks + StartValue;
 
        ++CurrentTick;
        return CurrentValue;
    }
 
    // Updates the target value without changing the duration or tick data.
    // Sets the state as if the new value was the target value all along
    void SetValueInterrupt(const float InValue)
    {
        if (IsDone())
        {
            CurrentValue = InValue;
        }
        else
        {
            DurationTicks = DurationTicks - CurrentTick;
            CurrentTick = 0;
            DeltaValue = InValue - CurrentValue;
            StartValue = CurrentValue;
        }
    }
 
    void SetValue(const float InValue, float InTimeSec = 0.0f)
    {
        DurationTicks = (int32)(SampleRate * InTimeSec);
        CurrentTick = 0;
 
        if (DurationTicks == 0)
        {
            CurrentValue = InValue;
        }
        else
        {
            DeltaValue = InValue - CurrentValue;
            StartValue = CurrentValue;
        }
    }
 
private:
 
    float StartValue;
    float CurrentValue;
    float DeltaValue;
    float SampleRate;
    int32 DurationTicks;
    int32 DefaultDurationTicks;
    int32 CurrentTick;
};