From 281b2f563709c5e08c81e8e5ceb9da75e70b7e58 Mon Sep 17 00:00:00 2001
From: Randy Heit <rheit@zdoom.fake>
Date: Thu, 12 Nov 2009 01:05:55 +0000
Subject: [PATCH] - Fixed: MBF sky Y offsets were ignored. X offsets should
 also be applied to   the sky cylinder, not the screen like Hexen scrolling
 skies.

SVN r1970 (trunk)
---
 docs/rh-log.txt |  4 ++++
 src/r_plane.cpp | 16 ++++++++++------
 2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/docs/rh-log.txt b/docs/rh-log.txt
index 0e29a173d..39251460b 100644
--- a/docs/rh-log.txt
+++ b/docs/rh-log.txt
@@ -1,3 +1,7 @@
+November 11, 2009
+- Fixed: MBF sky Y offsets were ignored. X offsets should also be applied to
+  the sky cylinder, not the screen like Hexen scrolling skies.
+
 November 9, 2009
 - Maps inside zips can now satisfy the map checks for IWAD detection.
 - Fixed: F7ZFile did not delete its Archive when destroyed.
diff --git a/src/r_plane.cpp b/src/r_plane.cpp
index 072518316..7ccbec09f 100644
--- a/src/r_plane.cpp
+++ b/src/r_plane.cpp
@@ -747,6 +747,8 @@ static angle_t skyflip;
 static int frontpos, backpos;
 static fixed_t frontyScale;
 static fixed_t frontcyl, backcyl;
+static fixed_t skymid;
+static angle_t skyangle;
 int frontiScale;
 
 extern fixed_t swall[MAXWIDTH];
@@ -764,14 +766,14 @@ static int skycolplace;
 // Get a column of sky when there is only one sky texture.
 static const BYTE *R_GetOneSkyColumn (FTexture *fronttex, int x)
 {
-	angle_t column = (viewangle + xtoviewangle[x]) ^ skyflip;
+	angle_t column = (skyangle + xtoviewangle[x]) ^ skyflip;
 	return fronttex->GetColumn((UMulScale16(column, frontcyl) + frontpos) >> FRACBITS, NULL);
 }
 
 // Get a column of sky when there are two overlapping sky textures
 static const BYTE *R_GetTwoSkyColumns (FTexture *fronttex, int x)
 {
-	DWORD ang = (viewangle + xtoviewangle[x]) ^ skyflip;
+	DWORD ang = (skyangle + xtoviewangle[x]) ^ skyflip;
 	DWORD angle1 = (DWORD)((UMulScale16(ang, frontcyl) + frontpos) >> FRACBITS);
 	DWORD angle2 = (DWORD)((UMulScale16(ang, backcyl) + backpos) >> FRACBITS);
 
@@ -849,7 +851,7 @@ static void R_DrawSky (visplane_t *pl)
 	rw_offset = 0;
 
 	frontyScale = rw_pic->yScale;
-	dc_texturemid = MulScale16 (skytexturemid/*-viewz*/, frontyScale);
+	dc_texturemid = MulScale16 (skymid, frontyScale);
 
 	if (1 << frontskytex->HeightBits == frontskytex->GetHeight())
 	{ // The texture tiles nicely
@@ -881,7 +883,7 @@ static void R_DrawSkyStriped (visplane_t *pl)
 	// So that I don't have to worry about fractional precision, chop off the
 	// fractional part of centeryfrac.
 	centeryfrac = centery << FRACBITS;
-	topfrac = (skytexturemid + iscale * (1-centery)) % (frontskytex->GetHeight() << FRACBITS);
+	topfrac = (skymid + iscale * (1-centery)) % (frontskytex->GetHeight() << FRACBITS);
 	if (topfrac < 0) topfrac += frontskytex->GetHeight() << FRACBITS;
 	yl = 0;
 	yh = (short)MulScale32 ((frontskytex->GetHeight() << FRACBITS) - topfrac, frontyScale);
@@ -1255,6 +1257,8 @@ void R_DrawSkyPlane (visplane_t *pl)
 		sky1tex = sky1texture;
 	}
 	sky2tex = sky2texture;
+	skymid = skytexturemid;
+	skyangle = viewangle;
 
 	if (pl->picnum == skyflatnum)
 	{
@@ -1311,10 +1315,10 @@ void R_DrawSkyPlane (visplane_t *pl)
 			// to allow sky rotation as well as careful positioning.
 			// However, the offset is scaled very small, so that it
 			// allows a long-period of sky rotation.
-			frontdpos = (-s->GetTextureXOffset(pos)) >> 6;
+			skyangle += s->GetTextureXOffset(pos);
 
 			// Vertical offset allows careful sky positioning.
-			dc_texturemid = s->GetTextureYOffset(pos) - 28*FRACUNIT;
+			skymid = s->GetTextureYOffset(pos) - 28*FRACUNIT;
 
 			// We sometimes flip the picture horizontally.
 			//