initHEADmain

1 files changed, 257 insertions, 0 deletions

diff --git a/mod/interp.c b/mod/interp.c
new file mode 100644
index 0000000..c5bbefb
--- /dev/null
+++ b/mod/interp.c
@@ -0,0 +1,257 @@
+/*
+ * melisma - extensible and scriptable audio engine
+ * Copyright (C) 2026  Ludvig Gunne Lindström
+ *
+ * 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 3 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, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <stdlib.h>
+#include <string.h>
+#include <lauxlib.h>
+#include "melisma.h"
+#include "mutil.h"
+
+#define INTERP_TYPENAME "interp"
+#define DEFAULT_METHOD "linear"
+
+struct interp;
+typedef float (*smp_fn)(float);
+
+enum {
+	LINEAR,
+	EASEIN,
+	EASEOUT,
+	SMOOTHSTEP,
+};
+
+struct interp
+{
+	ml_channel *out;
+	smp_fn      smp;
+	float       src;
+	float       dst;
+	size_t      t0;
+	size_t      t;
+	int         method;
+};
+
+static float sample(struct interp *ip)
+{
+	float x = ip->t0 == 0 ? 0 : (float)ip->t / (float)ip->t0;
+	switch (ip->method)
+	{
+	case LINEAR:
+		break;
+	case EASEIN:
+		x = x*x;
+		break;
+	case EASEOUT:
+		x = 1 -x;
+		x = 1 - x*x;
+		break;
+	case SMOOTHSTEP:
+		x = x*x*(3 - 2*x);
+		break;
+	}
+	return ip->src + x*(ip->dst - ip->src);
+}
+
+static void proc(const ml_proc_args *args)
+{
+	struct interp *ip = args->userp;
+
+	float *out = args->out[0];
+
+	for (size_t i = 0; i < args->nframes; i++)
+	{
+		out[i] = sample(ip);
+
+		if (ip->t == ip->t0)
+		{
+			ip->t = 0;
+			ip->t0 = 0;
+			ip->src = ip->dst;
+		}
+		else
+		{
+			ip->t++;
+		}
+	}
+}
+
+static int l_init(lua_State *s)
+{
+	float v = luaL_checknumber(s,1);
+
+	struct interp *ip = calloc(1,sizeof(*ip));
+	ip->src = v;
+	ip->dst = v;
+	ip->method = LINEAR;
+
+	ml_node *node = ml_create_node(proc,ip);
+	ml_label_node(node,"interp");
+	ip->out = ml_add_output(node);
+
+	*(void**) lua_newuserdata(s,sizeof(void*)) = ip;
+	luaL_setmetatable(s,INTERP_TYPENAME);
+
+	return 1;
+}
+
+static int l_set(lua_State *s)
+{
+	struct interp *ip = *(void**) luaL_checkudata(s,1,INTERP_TYPENAME);
+	float v = luaL_checknumber(s,2);
+
+	ip->src = v;
+	ip->dst = v;
+	ip->t0 = 0;
+	ip->t = 0;
+
+	return 0;
+}
+
+static int l_target(lua_State *s)
+{
+	int method_i = lua_upvalueindex(1);
+	int method = luaL_checkinteger(s,method_i);
+	struct interp *ip = *(void**) luaL_checkudata(s,1,INTERP_TYPENAME);
+	float v = luaL_checknumber(s,2);
+	float t = luaL_checknumber(s,3);
+
+	size_t sr = ml_sample_rate();
+
+	ip->src = sample(ip);
+	ip->dst = v;
+	ip->t0 = sr*t;
+	ip->t = 0;
+	ip->method = method;
+
+	return 0;
+}
+
+static int l_sample(lua_State *s)
+{
+	struct interp *ip = *(void**) luaL_checkudata(s,1,INTERP_TYPENAME);
+	lua_pushnumber(s,sample(ip));
+	return 1;
+}
+
+static int l_out(lua_State *s)
+{
+	struct interp *ip = *(void**) luaL_checkudata(s,1,INTERP_TYPENAME);
+	*(void**) lua_newuserdata(s,sizeof(void*)) = ip->out;
+	luaL_setmetatable(s,MELISMA_OUTPUT_CHANNEL_TYPENAME);
+	return 1;
+}
+
+int luaopen_melisma_interp(lua_State *s)
+{
+	ml_check_version();
+
+/*** Interpolation.
+
+	local minterp = require 'melisma.interp'
+	local mevent = require 'melisma.event'
+	local mgain = require 'melisma.gain'
+
+	local interp = minterp.init(0)
+
+	interp:linear(1,1)
+
+	mevent.schedule(0.5, function()
+		print('current value:', interp:sample())
+	end)
+
+	local sig = ...
+	local gain = mgain.linear(sig,interp)
+
+@classmod interp
+*/
+	lua_newtable(s);
+	int tbl = lua_gettop(s);
+
+/*** Initialize an interpolation unit.
+@static
+@function init
+@tparam number x0 Initial value.
+@treturn interp The newly created interpolation unit.
+*/
+	lua_pushcfunction(s,l_init);
+	lua_setfield(s,tbl,"init");
+
+/*** Set value directly.
+@function set
+@tparam number x New value.
+*/
+	lua_pushcfunction(s,l_set);
+	lua_setfield(s,tbl,"set");
+
+/*** Interpolate using linear interpolation.
+@function linear
+@tparam number v Target value.
+@tparam number t Interpolation time.
+*/
+	lua_pushnumber(s,LINEAR);
+	lua_pushcclosure(s,l_target,1);
+	lua_setfield(s,tbl,"linear");
+
+
+/*** Interpolate using ease-in interpolation.
+@function ease_in
+@tparam number v Target value.
+@tparam number t Interpolation time.
+*/
+	lua_pushnumber(s,EASEIN);
+	lua_pushcclosure(s,l_target,1);
+	lua_setfield(s,tbl,"ease_in");
+
+
+/*** Interpolate using ease-out interpolation.
+@function ease_out
+@tparam number v Target value.
+@tparam number t Interpolation time.
+*/
+	lua_pushnumber(s,EASEOUT);
+	lua_pushcclosure(s,l_target,1);
+	lua_setfield(s,tbl,"ease_out");
+
+/*** Interpolate using smoothstep interpolation.
+@function smoothstep
+@tparam number v Target value.
+@tparam number t Interpolation time.
+*/
+	lua_pushnumber(s,SMOOTHSTEP);
+	lua_pushcclosure(s,l_target,1);
+	lua_setfield(s,tbl,"smoothstep");
+
+/*** Get the current value.
+@function sample
+@treturn number The current value.
+*/
+	lua_pushcfunction(s,l_sample);
+	lua_setfield(s,tbl,"sample");
+
+	lua_pushcfunction(s,l_out);
+	lua_setfield(s,tbl,MUTIL_OUTPUT_CHANNEL_FUNCTION);
+
+	luaL_newmetatable(s,INTERP_TYPENAME);
+	int mt = lua_gettop(s);
+
+	lua_pushvalue(s,tbl);
+	lua_setfield(s,mt,"__index");
+
+	lua_settop(s,tbl);
+	return 1;
+}