From 2c7082a475bd94055b6c87818f177b4f167aa0da Mon Sep 17 00:00:00 2001
From: TehRealSalt <tehrealsalt@gmail.com>
Date: Sun, 8 Jul 2018 15:44:01 -0400
Subject: [PATCH] Internal sky improvement ports

Horizon lines, barrel sky distortion
---
 src/r_plane.c |  1 +
 src/r_segs.c  | 30 ++++++++++++++++++------------
 2 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/src/r_plane.c b/src/r_plane.c
index 3ec97efb..92e0cacb 100644
--- a/src/r_plane.c
+++ b/src/r_plane.c
@@ -714,6 +714,7 @@ void R_DrawPlanes(void)
 					if (dc_yl <= dc_yh)
 					{
 						angle = (pl->viewangle + xtoviewangle[x])>>ANGLETOSKYSHIFT;
+						dc_iscale = FixedMul(skyscale, FINECOSINE(xtoviewangle[x]>>ANGLETOFINESHIFT));
 						dc_x = x;
 						dc_source =
 							R_GetColumn(skytexture,
diff --git a/src/r_segs.c b/src/r_segs.c
index b997c2a8..025c920c 100644
--- a/src/r_segs.c
+++ b/src/r_segs.c
@@ -2674,22 +2674,28 @@ void R_StoreWallRange(INT32 start, INT32 stop)
 	worldbottomslope >>= 4;
 #endif
 
-	topstep = -FixedMul (rw_scalestep, worldtop);
-	topfrac = (centeryfrac>>4) - FixedMul (worldtop, rw_scale);
+	if (linedef->special == 41) { // HORIZON LINES
+		topstep = bottomstep = 0;
+		topfrac = bottomfrac = (centeryfrac>>4);
+		topfrac++; // Prevent 1px HOM
+	} else {
+		topstep = -FixedMul (rw_scalestep, worldtop);
+		topfrac = (centeryfrac>>4) - FixedMul (worldtop, rw_scale);
 
-	bottomstep = -FixedMul (rw_scalestep,worldbottom);
-	bottomfrac = (centeryfrac>>4) - FixedMul (worldbottom, rw_scale);
+		bottomstep = -FixedMul (rw_scalestep,worldbottom);
+		bottomfrac = (centeryfrac>>4) - FixedMul (worldbottom, rw_scale);
 
 #ifdef ESLOPE
-	if (frontsector->c_slope) {
-		fixed_t topfracend = (centeryfrac>>4) - FixedMul (worldtopslope, ds_p->scale2);
-		topstep = (topfracend-topfrac)/(range);
-	}
-	if (frontsector->f_slope) {
-		fixed_t bottomfracend = (centeryfrac>>4) - FixedMul (worldbottomslope, ds_p->scale2);
-		bottomstep = (bottomfracend-bottomfrac)/(range);
-	}
+		if (frontsector->c_slope) {
+			fixed_t topfracend = (centeryfrac>>4) - FixedMul (worldtopslope, ds_p->scale2);
+			topstep = (topfracend-topfrac)/(range);
+		}
+		if (frontsector->f_slope) {
+			fixed_t bottomfracend = (centeryfrac>>4) - FixedMul (worldbottomslope, ds_p->scale2);
+			bottomstep = (bottomfracend-bottomfrac)/(range);
+		}
 #endif
+	}
 
 	dc_numlights = 0;