diff --git a/solidify/gui_util.c b/solidify/gui_util.c
index 25e6005..dc155fd 100644
--- a/solidify/gui_util.c
+++ b/solidify/gui_util.c
@@ -11,11 +11,77 @@
  */
 
 
+#include <stdint.h>
+#include <math.h>
+#include <assert.h>
 #include <gtk/gtk.h>
 
 #include "gui_util.h"
 
 
+void hpoint(guchar *rgbbuf, int x, int y, int sx, uint8_t c[3])
+{
+	guchar *p = rgbbuf+(y*sx+x)*3;
+
+	p[0] = c[0];
+	p[1] = c[1];
+	p[2] = c[2];
+}
+
+
+void vpoint(guchar *rgbbuf, int y, int x, int sx, uint8_t c[3])
+{
+	guchar *p = rgbbuf+(y*sx+x)*3;
+
+	p[0] = c[0];
+	p[1] = c[1];
+	p[2] = c[2];
+}
+
+
+static void alpha(guchar *rgbbuf, int f, int i, int sx, uint8_t c[3], double w,
+    void (*point)(guchar *rgbbuf, int f, int i, int sx, uint8_t c[3]))
+{
+	uint8_t ct[3];
+	int n;
+
+	assert(w >= 0);
+	assert(w <= 1);
+	for (n = 0; n != 3; n++)
+		ct[n] = round(c[n]*w);
+	point(rgbbuf, f, i, sx, ct);
+}
+
+
+void aa_line(guchar *rgbbuf, int i, double fa, double fb, int max, int sx,
+    uint8_t c[3],
+    void (*point)(guchar *rgbbuf, int f, int i, int sx, uint8_t c[3]))
+{
+	int f0, f1;
+	int from, to, n;
+
+	assert(max > 0);
+	assert(fb >= fa);
+	f0 = floor(fa);
+	f1 = ceil(fb);
+	if (f0 > max || f1 < 0)
+		return;
+	if (f0 == f1) {
+		if (f0 >= 0 && f1 <= max)
+			point(rgbbuf, f0, i, sx, c);
+		return;
+	}
+	if (f0 >= 0)
+		alpha(rgbbuf, f0, i, sx, c, 1-(fa-f0), point);
+	if (f1 <= max)
+		alpha(rgbbuf, f1, i, sx, c, 1-(f1-fb), point);
+	from = f0+1 > 0 ? f0+1 : 0;
+	to = f1-1 < max ? f1-1: max;
+	for (n = from; n <= to; n++)
+		point(rgbbuf, n, i, sx, c);
+}
+
+
 void draw_circle(GdkDrawable *da, GdkGC *gc, int x, int y, int r)
 {
 	gdk_draw_arc(da, gc, FALSE, x-r, y-r, 2*r, 2*r, 0, 360*64);
diff --git a/solidify/gui_util.h b/solidify/gui_util.h
index fe3d8e6..49fe97a 100644
--- a/solidify/gui_util.h
+++ b/solidify/gui_util.h
@@ -13,9 +13,17 @@
 #ifndef GUI_UTIL_H
 #define GUI_UTIL_H
 
+#include <stdint.h>
 #include <gtk/gtk.h>
 
 
+void hpoint(guchar *rgbbuf, int x, int y, int sx, uint8_t c[3]);
+void vpoint(guchar *rgbbuf, int y, int x, int sx, uint8_t c[3]);
+
+void aa_line(guchar *rgbbuf, int i, double fa, double fb, int max, int sx,
+     uint8_t c[3],
+     void (*point)(guchar *rgbbuf, int f, int i, int sx, uint8_t c[3]));
+
 void draw_circle(GdkDrawable *da, GdkGC *gc, int x, int y, int r);
 
 #endif /* !GUI_UTIL_H */
diff --git a/solidify/level.c b/solidify/level.c
index c0425a3..df805fd 100644
--- a/solidify/level.c
+++ b/solidify/level.c
@@ -94,7 +94,9 @@ static void draw_image(GtkWidget *widget, struct face *f, int osd)
 
 static void draw_xz(GtkWidget *widget, struct face *f, int y)
 {
-	int x, z, z0;
+	int zm = f->a->max_z;
+	int x, z;
+	double z0;
 	guchar *rgbbuf, *p;
 
 	rgbbuf = p = calloc(f->sx*f->sz, 3);
@@ -105,19 +107,18 @@ static void draw_xz(GtkWidget *widget, struct face *f, int y)
 	if (y != -1)
 		for (x = 0; x != f->sx ; x++) {
 			z = get(f->a, x+f->a->min_x, y+f->a->min_y);
-			if (z != UNDEF) {
-				p = rgbbuf+3*(x+f->sx*(f->sz-z+f->a->min_z-1));
-				p[0] = 0xff;
-				p[1] = 0xff;
-				p[2] = 0xff;
-			}
-			z0 = round(face_z0(f, x, y));
-			/* @@@ anti-alias */
-			if (z0 >= f->a->min_z && z0 <= f->a->max_z) {
-				p = rgbbuf+3*(x+f->sx*(f->sz-z0+f->a->min_z-1));
-				p[0] = 0x80;
-				p[1] = 0xc0;
-				p[2] = 0xff;
+			z0 = face_z0(f, x, y);
+			if (z == UNDEF || z == z0) {
+				aa_line(rgbbuf, x, zm-z0, zm-z0, zm, f->sx,
+				    (uint8_t *) "\0\0\xff", vpoint);
+                                continue;
+                        }
+			if (z > z0) {
+				aa_line(rgbbuf, x, zm-z, zm-z0, zm, f->sx,
+				    (uint8_t *) "\0\xff\0", vpoint);
+			} else {
+				aa_line(rgbbuf, x, zm-z0, zm-z, zm, f->sx,
+				    (uint8_t *) "\xff\0\0", vpoint);
 			}
 		}
 	gdk_draw_rgb_image(widget->window,
@@ -130,7 +131,9 @@ static void draw_xz(GtkWidget *widget, struct face *f, int y)
 
 static void draw_zy(GtkWidget *widget, struct face *f, int x)
 {
-	int y, z, z0;
+	int zm = f->a->max_z;
+	int y, z;	
+	double z0;
 	guchar *rgbbuf, *p;
 
 	rgbbuf = p = calloc(f->sy*f->sz, 3);
@@ -140,20 +143,19 @@ static void draw_zy(GtkWidget *widget, struct face *f, int x)
 	}
 	if (x != -1)
 		for (y = 0; y != f->sy ; y++) {
-			z = get(f->a, x+f->a->min_x, y+f->a->min_y);
-			if (z != UNDEF) {
-				p = rgbbuf+3*(f->a->max_z-z+f->sz*(f->sy-y-1));
-				p[0] = 0xff;
-				p[1] = 0xff;
-				p[2] = 0xff;
+			z = get(f->a, x+f->a->min_x, f->a->max_y-y);
+			z0 = face_z0(f, x, f->sy-y-1);
+			if (z == UNDEF || z == z0) {
+				aa_line(rgbbuf, y, zm-z0, zm-z0, zm, f->sz,
+				    (uint8_t *) "\0\0\xff", hpoint);
+				continue;
 			}
-			z0 = round(face_z0(f, x, y));
-			/* @@@ anti-alias */
-			if (z0 >= f->a->min_z && z0 <= f->a->max_z) {
-				p = rgbbuf+3*(f->a->max_z-z0+f->sz*(f->sy-y-1));
-				p[0] = 0x80;
-				p[1] = 0xc0;
-				p[2] = 0xff;
+			if (z > z0) {
+				aa_line(rgbbuf, y, zm-z, zm-z0, zm, f->sz,
+				    (uint8_t *) "\0\xff\0", hpoint);
+			} else {
+				aa_line(rgbbuf, y, zm-z0, zm-z, zm, f->sz,
+				    (uint8_t *) "\xff\0\0", hpoint);
 			}
 		}
 	gdk_draw_rgb_image(widget->window,