From 054d81fc8eb0733c6f82b6f200c9c52d99243b73 Mon Sep 17 00:00:00 2001
From: Christoph Oelckers <coelckers@users.noreply.github.com>
Date: Sun, 12 Dec 2021 19:38:36 +0100
Subject: [PATCH] - fixed logic for discarding walls in new renderer.

The case being checked here may decide not to add the wall to the clipper but it must still be rendered.
Information for determining visibility is not sufficient in case of sector overlaps which can happen with rotating doors or poorly set up sector objects.

# Conflicts:
#	source/core/rendering/scene/hw_bunchdrawer.cpp
---
 .../core/rendering/scene/hw_bunchdrawer.cpp   | 21 +++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/source/core/rendering/scene/hw_bunchdrawer.cpp b/source/core/rendering/scene/hw_bunchdrawer.cpp
index 1a16b6448..724b5edb8 100644
--- a/source/core/rendering/scene/hw_bunchdrawer.cpp
+++ b/source/core/rendering/scene/hw_bunchdrawer.cpp
@@ -72,7 +72,6 @@ void BunchDrawer::Init(HWDrawInfo *_di, Clipper* c, vec2_t& view, binangle a1, b
 	for (int i = 0; i < numwalls; i++)
 	{
 		// Precalculate the clip angles to avoid doing this repeatedly during level traversal.
-		// Reverse the orientation so that startangle and endangle are properly ordered.
 		wall[i].clipangle = clipper->PointToAngle(wall[i].pos);
 	}
 	memset(sectionstartang, -1, sizeof(sectionstartang));
@@ -215,6 +214,7 @@ int BunchDrawer::ClipLine(int aline, bool portal)
 		return CL_Skip;
 	}
 	if (line >= 0 && blockwall[line]) return CL_Draw;
+	auto wal = &wall[line];
 
 	// convert to clipper coordinates and clamp to valid range.
 	int startAngle = startAngleBam.asbam();
@@ -228,13 +228,23 @@ int BunchDrawer::ClipLine(int aline, bool portal)
 
 	// check against the maximum possible viewing range of the sector.
 	// Todo: check if this is sufficient or if we really have to do a more costly check against the single visible segments.
+	// Note: These walls may be excluded from the clipper, but not from being drawn!
+	bool dontclip = false;
 	if (sectStartAngle != -1)
 	{
-		if (sectStartAngle > endAngle || sectEndAngle < startAngle) 
-			return CL_Skip; // completely outside the valid range for this sector.
+		if (sectStartAngle > endAngle || sectEndAngle < startAngle)
+		{
+			dontclip = true;
+		}
+		else
+		{
 		if (sectStartAngle > startAngle) startAngle = sectStartAngle;
 		if (sectEndAngle < endAngle) endAngle = sectEndAngle;
-		if (endAngle <= startAngle) return CL_Skip; // can this even happen?
+			if (endAngle <= startAngle)
+			{
+				return CL_Skip; // can this even happen?
+	}
+		}
 	}
 
 	if (!portal && !clipper->IsRangeVisible(startAngle, endAngle))
@@ -242,11 +252,10 @@ int BunchDrawer::ClipLine(int aline, bool portal)
 		return CL_Skip;
 	}
 
-	auto wal = &wall[line];
 	if (cline->partner == -1 || (wal->cstat & CSTAT_WALL_1WAY) || CheckClip(wal))
 	{
 		// one-sided
-		if (!portal) clipper->AddClipRange(startAngle, endAngle);
+		if (!portal && !dontclip) clipper->AddClipRange(startAngle, endAngle);
 		return CL_Draw;
 	}
 	else