step.cpp

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/*
 * Copyright (C) 2023  Christopher J. Howard
 *
 * This file is part of Antkeeper source code.
 *
 * Antkeeper source code 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 3 of the License, or
 * (at your option) any later version.
 *
 * Antkeeper source code 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 Antkeeper source code.  If not, see <http://www.gnu.org/licenses/>.
 */
 
#include <engine/animation/locomotion/step.hpp>
#include <engine/math/fract.hpp>
#include <cmath>
 
float step::phase(float t) const noexcept
{
    // Make phase relative to step stance
    t = math::fract(1.0f + t + delay - duty_factor);
    
    if (t < duty_factor)
    {
        // Stance phase, on `[-1, 0)`
        return (t - duty_factor) / duty_factor;
    }
    else
    {
        // Swing phase, on `[0, 1]`
        return (t - duty_factor) / (1.0f - duty_factor);
    }
}