arngment/synth.c

/*
 * arngment - random music generator
 *
 * Written in 2020 by Lucas
 *
 * To the extent possible under law, the author(s) have dedicated all
 * copyright and related and neighboring rights to this software to the
 * public domain worldwide. This software is distributed without any
 * warranty.
 *
 * You should have received a copy of the CC0 Public Domain Dedication
 * along with this software. If not, see
 * <http://creativecommons.org/publicdomain/zero/1.0/>.
 */

#include <math.h>

/*
 * Apparently, it's too hard for OSes to expose M_PI in a portable way.
 * Definition taken from
 *	$OpenBSD: math.h,v 1.36 2018/03/10 20:52:58 kettenis Exp $
 */
#define JUST_PI ((double)3.14159265358979323846)

#define CLAMP(x, a, b) ((x) < (a) ? (a) : (x) > (b) ? (b) : (x))

double
synth_distortion(double gain, double x)
{
	double xg = CLAMP(x * gain, -1.0, 1.0);
	return (x + xg) / 2.0;
}

double
synth_sinewave(double t, double a)
{
	return sin(2.0 * JUST_PI * t * a);
}

double
synth_trianglewave(double t, double a)
{
	double x = t * a;
	return 2.0 * fabs(2.0 * (x - floor(0.5 + x))) - 1.0;
}