diff --git a/solidify/array.c b/solidify/array.c
index f0a05aa..d7423e9 100644
--- a/solidify/array.c
+++ b/solidify/array.c
@@ -83,13 +83,3 @@ void set(struct array *a, int x, int y, int z)
 		a->data[x-a->min_x+(a->max_x-a->min_x+1)*(y-a->min_y)] = z;
 	}
 }
-
-
-int get_bounded(const struct array *a, int x, int y)
-{
-	if (x < a->min_x || x > a->max_x)
-		return UNDEF;
-	if (y < a->min_y || y > a->max_y)
-		return UNDEF;
-	return get(a, x, y);
-}
diff --git a/solidify/array.h b/solidify/array.h
index 0896eaa..0f4dd25 100644
--- a/solidify/array.h
+++ b/solidify/array.h
@@ -31,7 +31,6 @@ struct array *new_array(void);
 void free_array(struct array *a);
 
 void set(struct array *a, int x, int y, int z);
-int get_bounded(const struct array *a, int x, int y);
 
 
 static inline int get(const struct array *a, int x, int y)
@@ -39,4 +38,15 @@ static inline int get(const struct array *a, int x, int y)
 	return a->data[(x)-a->min_x+(a->max_x-a->min_x+1)*((y)-a->min_y)];
 }
 
+
+static inline int get_bounded(const struct array *a, int x, int y)
+{
+	if (x < a->min_x || x > a->max_x)
+		return UNDEF;
+	if (y < a->min_y || y > a->max_y)
+		return UNDEF;
+	return get(a, x, y);
+}
+
+
 #endif /* ARRAY_H */
diff --git a/solidify/overlap.c b/solidify/overlap.c
index 960fc47..572495c 100644
--- a/solidify/overlap.c
+++ b/solidify/overlap.c
@@ -51,7 +51,7 @@ static double r_center(const struct solid *s)
 static double ramp(int z0, double w0, int z1, double w1)
 {
 	if (z0 != UNDEF && z1 != UNDEF)
-		return w0 == 0 && w1 == 0 ? z0 : z0*w0+z1*w1;
+		return z0*w0+z1*w1;
 	if (z0 == UNDEF && z0 == UNDEF)
 		return UNDEF_F;
 	if (z0 == UNDEF && w0 < w1)
@@ -68,9 +68,9 @@ static double zmix(struct face *f, double x, double y)
 	double zx0, zx1;
 
 	xa = floor(x);
-	xb = ceil(x);
+	xb = xa+1;
 	ya = floor(y);
-	yb = ceil(y);
+	yb = ya+1;
 
 	zx0 = ramp(
 	    get_bounded(f->a, xa, ya), yb-y,
@@ -456,4 +456,17 @@ void overlap(GtkWidget *canvas, struct solid *s)
 	g_signal_connect(G_OBJECT(darea), "motion-notify-event",
 	    G_CALLBACK(motion_notify_event), s);
 
+if (0) {
+int i;
+long t0 = time(NULL);
+gtk_widget_show_all(canvas);
+for (i = 0; i != 1000; i++) {
+	rotate(&s->a->m, 100);
+	draw_image(darea, s, 0);
+	while (gtk_events_pending())
+		gtk_main_iteration();
+}
+fprintf(stderr, "%lu\n", time(NULL)-t0);
+}
+
 }