daynightratio.h

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// Luanti
// SPDX-License-Identifier: LGPL-2.1-or-later
// Copyright (C) 2010-2013 celeron55, Perttu Ahola <celeron55@gmail.com>
 
#pragma once
 
inline u32 time_to_daynight_ratio(float time_of_day, bool smooth)
{
        float t = time_of_day;
        if (t < 0.0f)
                t += ((int)(-t) / 24000) * 24000.0f;
        if (t >= 24000.0f)
                t -= ((int)(t) / 24000) * 24000.0f;
        if (t > 12000.0f)
                t = 24000.0f - t;
 
        const float values[9][2] = {
                {4250.0f + 125.0f, 175.0f},
                {4500.0f + 125.0f, 175.0f},
                {4750.0f + 125.0f, 250.0f},
                {5000.0f + 125.0f, 350.0f},
                {5250.0f + 125.0f, 500.0f},
                {5500.0f + 125.0f, 675.0f},
                {5750.0f + 125.0f, 875.0f},
                {6000.0f + 125.0f, 1000.0f},
                {6250.0f + 125.0f, 1000.0f},
        };
 
        if (!smooth) {
                float lastt = values[0][0];
                for (u32 i = 1; i < 9; i++) {
                        float t0 = values[i][0];
                        float switch_t = (t0 + lastt) / 2.0f;
                        lastt = t0;
                        if (switch_t <= t)
                                continue;
 
                        return values[i][1];
                }
                return 1000;
        }
 
        if (t <= 4625.0f) // 4500 + 125
                return values[0][1];
        else if (t >= 6125.0f) // 6000 + 125
                return 1000;
 
        for (u32 i = 0; i < 9; i++) {
                if (values[i][0] <= t)
                        continue;
 
                float td0 = values[i][0] - values[i - 1][0];
                float f = (t - values[i - 1][0]) / td0;
                return f * values[i][1] + (1.0f - f) * values[i - 1][1];
        }
        return 1000;
}