diff -urN wf-/data.c wf/data.c
--- wf-/data.c	Wed Jan 13 00:00:00 2016
+++ wf/data.c	Sun Jan 17 00:00:00 2016
@@ -19,6 +19,7 @@
 	CASE_RET(type_circle);
 	CASE_RET(type_circle_y);
 	CASE_RET(type_circle_x);
+	CASE_RET(type_curve);
 	CASE_RET(type_ball);
 	CASE_RET(type_arc);
 	CASE_RET(type_octahedron);
@@ -303,6 +304,31 @@
 }
 
 static void
+curve_draw(struct curve *cv, prm_t *prm)
+{
+	int i, n = cv->n;
+	d3_t p[256*2];
+	int odr[256+3];
+	data_t data = {
+		type_wire_frame,
+		&(struct wire_frame){ n, cv->ps, odr, p, &p[n] }
+	};
+	data_t op = {
+		type_rdiv,
+		&(struct rdiv){ cv->div_n, 1 }
+	};
+
+	if(cv->n > 256) ERR("cv->n > 256");
+
+	for(i=0; i<n; i++) odr[i] = i;
+	if(cv->closed) odr[i++] = 0;
+	odr[i] = odr[i+1] = -1;
+
+	if(cv->div_n <= 0) data_draw(&data, prm);
+	else op_data_draw(&op, &data, prm);
+}
+
+static void
 ball_draw(struct ball *ball, prm_t *prm)
 {
 	data_t op = { type_arr, (data_t[]){
@@ -421,6 +447,9 @@
 		break;
 	case type_circle_x:
 		circle_x_draw(data->p, prm);
+		break;
+	case type_curve:
+		curve_draw(data->p, prm);
 		break;
 	case type_ball:
 		ball_draw(data->p, prm);
diff -urN wf-/data.h wf/data.h
--- wf-/data.h	Wed Jan 13 00:00:00 2016
+++ wf/data.h	Sun Jan 17 00:00:00 2016
@@ -21,6 +21,7 @@
 #define type_circle			5
 #define type_circle_y			21
 #define type_circle_x			22
+#define type_curve			30
 
 #define type_ball			6
 #define type_arc			7
@@ -80,6 +81,13 @@
 struct circle{
 	double r;
 	int n;
+};
+
+struct curve{
+	int n;
+	pos_t *ps;
+	int closed;
+	int div_n;
 };
 
 struct ball{
diff -urN wf-/wf_ex.c wf/wf_ex.c
--- wf-/wf_ex.c	Sat Jan 16 00:00:00 2016
+++ wf/wf_ex.c	Sun Jan 17 00:00:00 2016
@@ -411,6 +411,14 @@
 		    { type_end } }},
 		  .data = { type_cube } }};
 
+		data_t *rail1 = &(data_t){ type_op_data_set, &(struct op_data_set){
+		  .op = { type_slide, &(d3_t){0,-4*a,0} },
+		  .data = { type_curve, &(struct curve){.n=rail->n,.ps=rail->ps,.closed=1,.div_n=10} } }};
+
+		data_t *rail2 = &(data_t){ type_op_data_set, &(struct op_data_set){
+		  .op = { type_slide, &(d3_t){0,-4*a,-a*0.5} },
+		  .data = { type_curve, &(struct curve){.n=rail->n,.ps=rail->ps,.closed=1,.div_n=0} } }};
+
 		data_t *matryoshka = &(data_t){ type_op_data_set, &(struct op_data_set){
 		  .op = { type_arr, (data_t[]){
 		    { type_slide, &(d3_t){20,20,20} },
@@ -504,7 +512,7 @@
 			*exile, *lissajours,
 			*half_pipe,
 			*fireworks,
-			*train,
+			*train, *rail1, *rail2,
 			*matryoshka,
 			*clock,
 			*ripple, *wave,