Steps::PredictMeter()

Steps.cpp

float Steps::PredictMeter() const
{
    // Aldo_MX: I'm calculating the meter taking into account the step density.
    // It will just give a "base value", you need to increase the value if you
    // use pivots and/or it's a gimmicky chart.
    //
    // In other words, this value should be considered the "minimum possible"
    // meter value using 1 ~ 10 difficulty scale.
    //
    // The following formula is used ONLY with checkpoint combinations possible
    // with one press (ie. up to quads in double)*:
    //
    //      - 1 / (NumCheckpoints * 4)
    //
    // *If the song has too many single holds like Love is a Danger Zone CZ, the
    // substracted value should not be greater than 25% of the total value.
    //
    // The following formula is used with any other combination:
    //
    //      SQRT( (NumCheckpoints ^ 1.5) + (NumSteps ^ 1.5) )
    //
    // If the combination is NOT possible with one press (ex. quads in single),
    // the result gets multiplied by 2.
    //
    // The total value gets divided by the steps length in seconds to get
    // the predicted meter value.
    //
    // EDIT: We multiply by 3 and substract 1.5 (substract only in Single Modes)
    // to get meter values similar to NX2 ~ NXA

    int iMaxPossibleCols = 4;

    switch (m_StepsType)
    {
    case STEPS_TYPE_PUMP_SINGLE:
    case STEPS_TYPE_PUMP_COUPLE:
        iMaxPossibleCols--;
    }

    float fStepsLengthInSeconds = m_Timing.GetElapsedTimeFromBeat(
                                      notes->GetLastBeat()
                                  );

    float fDifficulty = 0;
    float fHoldDifficultyToDecrease = 0;

    // Load TimingData to apply tickcounts
    NoteDataUtil::ParseTiming( *notes, m_Timing, true );

    for (int r=0; r < notes->GetNumRows(); ++r)
    {
        int iColsWithAny = notes->GetNumColsWithCheckpoint(r, false),
            // Do not count hold heads as checkpoints!
            // Phantom-style Holds will increase the base difficulty :/, but
            // holds should not decrease the difficulty before a certain amount
            // of combo...
            iColsWithHoldBodyOrTail = notes->GetNumColsWithCheckpoint(r, true, true);

        // No Steps in this row
        if (iColsWithAny <= 0)
            continue;

        int iColsWithNotes = iColsWithAny - iColsWithHoldBodyOrTail;

        // Only checkpoints
        if (iColsWithNotes <= 0)
        {
            // Combinations possible with a single press
            if (iColsWithHoldBodyOrTail <= iMaxPossibleCols)
                fHoldDifficultyToDecrease += 1.f / (iColsWithHoldBodyOrTail*4);

            // Combinations NOT possible with a single press
            else
                fDifficulty += sqrt(powf((float)iColsWithHoldBodyOrTail, 1.5f))
                               * 2.f;
        }
        // Checkpoints and steps or only steps in this row
        else
        {
            // Any combination
            float fValueToAdd = sqrt(powf((float)iColsWithHoldBodyOrTail, 1.5f)
                                + powf((float)iColsWithNotes, 1.5f));

            // Combinations NOT possible with a single press, multiply by 2
            if (iColsWithAny > iMaxPossibleCols)
                fValueToAdd *= 2;

            fDifficulty += fValueToAdd;
        }
    }

    // Revert NoteData
    NoteDataUtil::UnparseTiming( *notes, m_Timing, true );

    // Substract a maximum of 25%
    fHoldDifficultyToDecrease = min(fHoldDifficultyToDecrease, fDifficulty*.25f);
    fDifficulty -= fHoldDifficultyToDecrease;

    // Divide by the steps length in seconds
    fDifficulty /= fStepsLengthInSeconds;

    // HACK: Adjust the final value to get NX2~NXA-like values...
    fDifficulty *= 3.0f;
    if (iMaxPossibleCols == 3)
        fDifficulty -= 1.50000001f;

    // Lowest value should be 1
    fDifficulty = max(fDifficulty, 1.f);

    return fDifficulty;
}

/*
 * StepMania AMX is (c) 2008-2017 Aldo Fregoso "Aldo_MX".
 * All rights reserved.
 * 
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 */