initHEADmain

1 files changed, 173 insertions, 0 deletions

diff --git a/mod/spring.c b/mod/spring.c
new file mode 100644
index 0000000..a6f96ea
--- /dev/null
+++ b/mod/spring.c
@@ -0,0 +1,173 @@
+/*
+ * 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 <stdbool.h>
+#include <math.h>
+#include <lauxlib.h>
+#include "melisma.h"
+
+#define SPRING_TYPENAME "spring"
+
+struct spring
+{
+	ml_node  *node;
+	float     target;
+	float     value;
+	float     freq;
+	float     damping;
+	float     velocity;
+	bool      mapped;
+};
+
+static void proc(const ml_proc_args *args)
+{
+	struct spring *spring = args->userp;
+
+	float *out = args->out[0];
+	float *mapped = spring->mapped ? args->in[0] : NULL;
+	float dt = 1.f/ml_sample_rate();
+
+	for (size_t i = 0; i < args->nframes; i++)
+	{
+		float target = mapped ? mapped[i] : spring->target;
+		float w = 2*M_PI*spring->freq;
+		float f = (target - spring->value)*w*w;
+		float d = 2*w*spring->velocity*spring->damping;
+		float a = f - d;
+
+		spring->velocity += a*dt;
+		spring->value += spring->velocity*dt;
+
+		out[i] = spring->value;
+	}
+}
+
+static int l_damping(lua_State *s)
+{
+	struct spring *spring = *(void**) luaL_checkudata(s,1,SPRING_TYPENAME);
+	float x = luaL_checknumber(s,2);
+	spring->damping = x;
+	return 0;
+}
+
+static int l_freq(lua_State *s)
+{
+	struct spring *spring = *(void**) luaL_checkudata(s,1,SPRING_TYPENAME);
+	float x = luaL_checknumber(s,2);
+	spring->freq = x;
+	return 0;
+}
+
+static int l_target(lua_State *s)
+{
+	struct spring *spring = *(void**) luaL_checkudata(s,1,SPRING_TYPENAME);
+	float x = luaL_checknumber(s,2);
+	spring->target = x;
+	return 0;
+}
+
+static int l_map(lua_State *s)
+{
+	struct spring *spring = *(void**) luaL_checkudata(s,1,SPRING_TYPENAME);
+
+	if (spring->mapped)
+	{
+		luaL_error(s,"already mapped");
+	}
+
+	ml_channel *src = *(void**) luaL_checkudata(s,2,MELISMA_OUTPUT_CHANNEL_TYPENAME);
+	ml_channel *dst = ml_add_input(spring->node);
+	ml_connect(src,dst);
+
+	spring->mapped = true;
+
+	return 0;
+}
+
+static int l_sample(lua_State *s)
+{
+	struct spring *spring = *(void**) luaL_checkudata(s,1,SPRING_TYPENAME);
+	lua_pushnumber(s,spring->value);
+	return 1;
+}
+
+static int l_call(lua_State *s)
+{
+	struct spring *spring = *(void**) luaL_checkudata(s,1,SPRING_TYPENAME);
+	*(void**) lua_newuserdata(s,sizeof(void*)) = ml_get_output(spring->node,0);
+	luaL_setmetatable(s,MELISMA_OUTPUT_CHANNEL_TYPENAME);
+	return 1;
+}
+
+static int l_init(lua_State *s)
+{
+	float value = luaL_checknumber(s,1);
+	float freq = luaL_checknumber(s,2);
+	float damping = luaL_checknumber(s,3);
+
+	struct spring *spring = calloc(1,sizeof(*spring));
+	spring->value = value;
+	spring->freq = freq;
+	spring->damping = damping;
+	spring->mapped = false;
+
+	spring->node = ml_create_node(proc,spring);
+	ml_add_output(spring->node);
+
+	*(void**) lua_newuserdata(s,sizeof(void*)) = spring;
+	luaL_setmetatable(s,SPRING_TYPENAME);
+
+	return 1;
+}
+
+int luaopen_melisma_spring(lua_State *s)
+{
+	lua_newtable(s);
+	int tbl = lua_gettop(s);
+
+	lua_pushcfunction(s,l_init);
+	lua_setfield(s,tbl,"init");
+
+	lua_pushcfunction(s,l_freq);
+	lua_setfield(s,tbl,"freq");
+
+	lua_pushcfunction(s,l_damping);
+	lua_setfield(s,tbl,"damping");
+
+	lua_pushcfunction(s,l_target);
+	lua_setfield(s,tbl,"target");
+
+	lua_pushcfunction(s,l_sample);
+	lua_setfield(s,tbl,"sample");
+
+	lua_pushcfunction(s,l_map);
+	lua_setfield(s,tbl,"map");
+
+	luaL_newmetatable(s,SPRING_TYPENAME);
+	int mt = lua_gettop(s);
+
+	lua_pushvalue(s,tbl);
+	lua_setfield(s,mt,"__index");
+
+	lua_pushcfunction(s,l_call);
+	lua_setfield(s,mt,"__call");
+
+	lua_settop(s,tbl);
+	return 1;
+}