From 1c2dcad36e6b2d568225884f46f3257b820a73da Mon Sep 17 00:00:00 2001
From: Magnus Norddahl <dpjudas@users.noreply.github.com>
Date: Thu, 20 Oct 2016 15:16:02 +0200
Subject: [PATCH] Fix linear skies

---
 src/r_plane.cpp | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/r_plane.cpp b/src/r_plane.cpp
index be8247d26..3ba6feaf7 100644
--- a/src/r_plane.cpp
+++ b/src/r_plane.cpp
@@ -1098,7 +1098,15 @@ static void R_DrawSkyColumnStripe(int start_x, int y1, int y2, int columns, doub
 
 		DWORD ang, angle1, angle2;
 
-		ang = (skyangle + xtoviewangle[x]) ^ skyflip;
+		if (r_linearsky)
+		{
+			angle_t xangle = (angle_t)((0.5 - x / (double)viewwidth) * FocalTangent * ANGLE_90);
+			ang = (skyangle + xangle) ^ skyflip;
+		}
+		else
+		{
+			ang = (skyangle + xtoviewangle[x]) ^ skyflip;
+		}
 		angle1 = (DWORD)((UMulScale16(ang, frontcyl) + frontpos) >> FRACBITS);
 		angle2 = (DWORD)((UMulScale16(ang, backcyl) + backpos) >> FRACBITS);