diff --git a/solidify/povray.c b/solidify/povray.c
index ac8e70a..4b42663 100644
--- a/solidify/povray.c
+++ b/solidify/povray.c
@@ -100,7 +100,7 @@ static void povray_face(const struct face *f, const char *side,
 "\t}\n", prefix, side,
     f->sx*f->x_step, (f->sz-1)*f->z_step, f->sy*f->y_step,
     -f->sx*f->x_step/2, f->sy*f->y_step/2,
-    -atan(f->fy)/M_PI*180, -atan(f->fx)/M_PI*180,
+    -atan(f->fy)/M_PI*180, atan(f->fx)/M_PI*180,
     f->a->min_z*f->z_step,
     -f->z_ref*f->z_step,
     a,
diff --git a/solidify/project.c b/solidify/project.c
index 7d14625..28a4582 100644
--- a/solidify/project.c
+++ b/solidify/project.c
@@ -72,7 +72,7 @@ static void read_face_data(FILE *file, struct face *f)
 
 	if (fscanf(file, "%f", &v) != 1)
 		return;
-	f->fx = tan(v/180*M_PI);
+	f->fx = -tan(v/180*M_PI);
 
 	if (fscanf(file, "%f", &v) != 1)
 		return;
@@ -163,7 +163,7 @@ static void save_face_data(FILE *file, const char *name, const struct face *f)
 		a = 180-a;
 	if (fprintf(file, "%g %g %g\n%g %g %g\n",
 	    f->z_ref*f->z_step,
-	    atan(f->fx)/M_PI*180, atan(f->fy)/M_PI*180,
+	    -atan(f->fx)/M_PI*180, atan(f->fy)/M_PI*180,
 	    a, f->m.b[0]*f->x_step, f->m.b[1]*f->y_step) < 0) {
 		perror(name);
 		exit(1);