From cc1def8d77a5edd5c2ae9f74c259f54a1210ecf3 Mon Sep 17 00:00:00 2001
From: Christoph Oelckers <coelckers@users.noreply.github.com>
Date: Sun, 23 May 2021 09:15:53 +0200
Subject: [PATCH] - fixed: When the node builder is used for triangulation, all
 zero-length lines must be eliminated first.

These can cause triangulation errors.
---
 source/core/sectorgeometry.cpp | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/source/core/sectorgeometry.cpp b/source/core/sectorgeometry.cpp
index 68c1cb6c1..c7f3c9f25 100644
--- a/source/core/sectorgeometry.cpp
+++ b/source/core/sectorgeometry.cpp
@@ -369,6 +369,14 @@ bool SectorGeometry::MakeVertices2(unsigned int secnum, int plane, const FVector
 	for (unsigned i = 0; i < lines.Size(); i++)
 	{
 		auto p1 = lines[i].v1->p, p2 = lines[i].v2->p;
+
+		// Throw out any line with zero length.
+		if (p1 == p2)
+		{
+			lines.Delete(i);
+			continue;
+		}
+
 		for (unsigned j = i + 1; j < lines.Size(); j++)
 		{
 			auto pp1 = lines[j].v1->p, pp2 = lines[j].v2->p;