llcriticaldamp.cpp

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#include "linden_common.h"

#include "llcriticaldamp.h"

//-----------------------------------------------------------------------------
// static members
//-----------------------------------------------------------------------------
LLFrameTimer LLCriticalDamp::sInternalTimer;
std::map<F32, F32> LLCriticalDamp::sInterpolants;
F32 LLCriticalDamp::sTimeDelta;

//-----------------------------------------------------------------------------
// LLCriticalDamp()
//-----------------------------------------------------------------------------
LLCriticalDamp::LLCriticalDamp()
{
        sTimeDelta = 0.f;
}

// static
//-----------------------------------------------------------------------------
// updateInterpolants()
//-----------------------------------------------------------------------------
void LLCriticalDamp::updateInterpolants()
{
        sTimeDelta = sInternalTimer.getElapsedTimeAndResetF32();

        F32 time_constant;

        for (std::map<F32, F32>::iterator iter = sInterpolants.begin();
                 iter != sInterpolants.end(); iter++)
        {
                time_constant = iter->first;
                F32 new_interpolant = 1.f - pow(2.f, -sTimeDelta / time_constant);
                new_interpolant = llclamp(new_interpolant, 0.f, 1.f);
                sInterpolants[time_constant] = new_interpolant;
        }
} 

//-----------------------------------------------------------------------------
// getInterpolant()
//-----------------------------------------------------------------------------
F32 LLCriticalDamp::getInterpolant(const F32 time_constant, BOOL use_cache)
{
        if (time_constant == 0.f)
        {
                return 1.f;
        }

        if (use_cache && sInterpolants.count(time_constant))
        {
                return sInterpolants[time_constant];
        }
        
        F32 interpolant = 1.f - pow(2.f, -sTimeDelta / time_constant);
        interpolant = llclamp(interpolant, 0.f, 1.f);
        if (use_cache)
        {
                sInterpolants[time_constant] = interpolant;
        }

        return interpolant;
}

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