From f9795a25334f0deff827f17b29dac0158cbf5c34 Mon Sep 17 00:00:00 2001
From: raa-eruanna <eruanna@drdteam.org>
Date: Mon, 3 Oct 2016 21:39:15 -0400
Subject: [PATCH] Revert "Remove linear sky again"

This reverts commit 21390e91b8a28c71ba44bf62ee3c7545508a74e2.

- also set r_linearsky to "false" by default.
---
 src/r_plane.cpp | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/src/r_plane.cpp b/src/r_plane.cpp
index 0cfd51ca56..cfc30e1c7b 100644
--- a/src/r_plane.cpp
+++ b/src/r_plane.cpp
@@ -859,16 +859,30 @@ static DWORD lastskycol_bgra[4];
 static int skycolplace;
 static int skycolplace_bgra;
 
+CVAR(Bool, r_linearsky, false, CVAR_ARCHIVE | CVAR_GLOBALCONFIG);
+
 // Get a column of sky when there is only one sky texture.
 static const BYTE *R_GetOneSkyColumn (FTexture *fronttex, int x)
 {
-	angle_t column = (skyangle + xtoviewangle[x]) ^ skyflip;
-	int tx = (UMulScale16(column, frontcyl) + frontpos) >> FRACBITS;
+	int tx;
+	if (r_linearsky)
+	{
+		angle_t xangle = (angle_t)((0.5 - x / (double)viewwidth) * FocalTangent * ANGLE_90);
+		angle_t column = (skyangle + xangle) ^ skyflip;
+		tx = (UMulScale16(column, frontcyl) + frontpos) >> FRACBITS;
+	}
+	else
+	{
+		angle_t column = (skyangle + xtoviewangle[x]) ^ skyflip;
+		tx = (UMulScale16(column, frontcyl) + frontpos) >> FRACBITS;
+	}
 
 	if (!r_swtruecolor)
 		return fronttex->GetColumn(tx, NULL);
 	else
+	{
 		return (const BYTE *)fronttex->GetColumnBgra(tx, NULL);
+	}
 }
 
 // Get a column of sky when there are two overlapping sky textures