From 3edbf0a085cd17366f854525aae8aa30b55b9fe8 Mon Sep 17 00:00:00 2001
From: Monster Iestyn <iestynjealous@ntlworld.com>
Date: Wed, 19 Apr 2017 22:19:46 +0100
Subject: [PATCH] Fixed P_CheckSight not considering polyobject top and bottom
 at all

This was actually kind of easier to do than I expected, though I can't tell if there's anything else I need to do or not
---
 src/p_sight.c | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/src/p_sight.c b/src/p_sight.c
index bd6ab4d73..132f993cf 100644
--- a/src/p_sight.c
+++ b/src/p_sight.c
@@ -103,12 +103,20 @@ static fixed_t P_InterceptVector2(divline_t *v2, divline_t *v1)
 static boolean P_CrossSubsecPolyObj(polyobj_t *po, register los_t *los)
 {
 	size_t i;
+	sector_t *polysec;
+
+	if (!(po->flags & POF_RENDERALL))
+		return true; // the polyobject isn't visible, so we can ignore it
+
+	polysec = po->lines[0]->backsector;
 
 	for (i = 0; i < po->numLines; ++i)
 	{
 		line_t *line = po->lines[i];
 		divline_t divl;
 		const vertex_t *v1,*v2;
+		fixed_t frac;
+		fixed_t topslope, bottomslope;
 
 		// already checked other side?
 		if (line->validcount == validcount)
@@ -140,7 +148,22 @@ static boolean P_CrossSubsecPolyObj(polyobj_t *po, register los_t *los)
 			continue;
 
 		// stop because it is not two sided
-		return false;
+		//if (!(po->flags & POF_TESTHEIGHT))
+			//return false;
+
+		frac = P_InterceptVector2(&los->strace, &divl);
+
+		// get slopes of top and bottom of this polyobject line
+		topslope = FixedDiv(polysec->ceilingheight - los->sightzstart , frac);
+		bottomslope = FixedDiv(polysec->floorheight - los->sightzstart , frac);
+
+		if (topslope >= los->topslope && bottomslope <= los->bottomslope)
+			return false; // view completely blocked
+
+		// TODO: figure out if it's worth considering partially blocked cases or not?
+		// maybe to adjust los's top/bottom slopes if needed
+		//if (los->topslope <= los->bottomslope)
+			//return false;
 	}
 
 	return true;