From 549569e75b4c072a54d9ab39926521c6cc198895 Mon Sep 17 00:00:00 2001
From: MascaraSnake <jonassauer27@gmail.com>
Date: Wed, 5 Jan 2022 10:08:49 +0100
Subject: [PATCH] Fix offset calculation for segs that represent linedef
 backsides

---
 src/p_setup.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/p_setup.c b/src/p_setup.c
index 7f9674e4e..de91f4674 100644
--- a/src/p_setup.c
+++ b/src/p_setup.c
@@ -2494,7 +2494,10 @@ static boolean P_LoadExtendedSubsectorsAndSegs(UINT8 **data, nodetype_t nodetype
 		P_InitializeSeg(seg);
 		seg->angle = R_PointToAngle2(v1->x, v1->y, v2->x, v2->y);
 		if (seg->linedef)
-			segs[i].offset = FixedHypot(v1->x - seg->linedef->v1->x, v1->y - seg->linedef->v1->y);
+		{
+			vertex_t *v = (seg->side == 1) ? seg->linedef->v2 : seg->linedef->v1;
+			segs[i].offset = FixedHypot(v1->x - v->x, v1->y - v->y);
+		}
 		seg->length = P_SegLength(seg);
 #ifdef HWRENDER
 		seg->flength = (rendermode == render_opengl) ? P_SegLengthFloat(seg) : 0;