minetest/src/daynightratio.h

/*
Minetest
Copyright (C) 2010-2013 celeron55, Perttu Ahola <celeron55@gmail.com>

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 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 Lesser General Public License for more details.

You should have received a copy of the GNU Lesser 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.
*/

#pragma once

inline u32 time_to_daynight_ratio(float time_of_day, bool smooth)
{
	float t = time_of_day;
	if(t < 0)
		t += ((int)(-t)/24000)*24000;
	if(t >= 24000)
		t -= ((int)(t)/24000)*24000;
	if(t > 12000)
		t = 24000 - t;
	float values[][2] = {
		{4250+125, 150},
		{4500+125, 150},
		{4750+125, 250},
		{5000+125, 350},
		{5250+125, 500},
		{5500+125, 675},
		{5750+125, 875},
		{6000+125, 1000},
		{6250+125, 1000},
	};
	if(!smooth){
		float lastt = values[0][0];
		for(u32 i=1; i<sizeof(values)/sizeof(*values); i++){
			float t0 = values[i][0];
			float switch_t = (t0 + lastt) / 2;
			lastt = t0;
			if(switch_t <= t)
				continue;
			return values[i][1];
		}
		return 1000;
	}

	for (u32 i=0; i < sizeof(values) / sizeof(*values); i++) {
			if (values[i][0] <= t)
				continue;
			if (i == 0)
				return values[i][1];
			float td0 = values[i][0] - values[i-1][0];
			float f = (t - values[i-1][0]) / td0;
			return f * values[i][1] + (1.0 - f) * values[i-1][1];
		}
		return 1000;

}