From 3f2c6cdc302fd84228be06030a0fdf55d5543780 Mon Sep 17 00:00:00 2001
From: Werner Almesberger <werner@almesberger.net>
Date: Thu, 8 Jan 2015 00:14:21 -0300
Subject: [PATCH] slicer/slice.c (add): only output lower end of vertical walls
 (still needs work)

---
 slicer/slice.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/slicer/slice.c b/slicer/slice.c
index 8022edd..167bb07 100644
--- a/slicer/slice.c
+++ b/slicer/slice.c
@@ -79,6 +79,8 @@ static void add(const struct v *a, const struct v *b, const struct v *c)
 fprintf(stderr, "zero point\n");
 		return;
 	}
+	if (c->z < a->z)
+		return;
 	z = get_z(a->z);
 	line = alloc_type(struct line);
 	line->ax = a->x;