- some Transfer_Heights related optimizations.

* only call hw_CheckViewArea if the result is not known yet.
* check the map up front if it even contains heightsecs. This allows to shortcut the above check entirely for maps without sector transfers and will allow further optimizations.

(cherry picked from commit 3c49804c6c)

# Conflicts:
#	src/gl/scene/gl_bsp.cpp
#	src/gl/scene/gl_fakeflat.cpp
#	src/hwrenderer/scene/hw_fakeflat.h

src/g_level.cpp

@@ -1472,6 +1472,7 @@ void G_InitLevelLocals ()
 	level.Music = info->Music;
 	level.musicorder = info->musicorder;
 	level.MusicVolume = 1.f;
+	level.HasHeightSecs = false;
 
 	level.LevelName = level.info->LookupLevelName();
 	level.NextMap = info->NextMap;

src/g_levellocals.h

@@ -141,6 +141,7 @@ struct FLevelLocals
 	int8_t		WallHorizLight;
 
 	bool		FromSnapshot;			// The current map was restored from a snapshot
+	bool		HasHeightSecs;			// true if some Transfer_Heights effects are present in the map. If this is false, some checks in the renderer can be shortcut.
 
 	double		teamdamage;
 

src/gl/scene/gl_bsp.cpp

@@ -147,7 +147,7 @@ void GLSceneDrawer::AddLine (seg_t *seg, bool portalclip)
 		else
 		{
 			// clipping checks are only needed when the backsector is not the same as the front sector
-			CheckViewArea(seg->v1, seg->v2, seg->frontsector, seg->backsector);
+			if (in_area == area_default) in_area = CheckViewArea(seg->v1, seg->v2, seg->frontsector, seg->backsector);
 
 			backsector = gl_FakeFlat(seg->backsector, &bs, in_area, true);
 

src/gl/scene/gl_fakeflat.cpp

@@ -156,13 +156,14 @@ bool gl_CheckClip(side_t * sidedef, sector_t * frontsector, sector_t * backsecto
 
 //==========================================================================
 //
-// check for levels with exposed lower areas
+// check for levels with exposed lower areas. May only be called if actual
+// state is not known yet!
 //
 //==========================================================================
 
-void GLSceneDrawer::CheckViewArea(vertex_t *v1, vertex_t *v2, sector_t *frontsector, sector_t *backsector)
+area_t GLSceneDrawer::CheckViewArea(vertex_t *v1, vertex_t *v2, sector_t *frontsector, sector_t *backsector)
 {
-	if (in_area == area_default &&
+	if (
 		(backsector->heightsec && !(backsector->heightsec->MoreFlags & SECF_IGNOREHEIGHTSEC)) &&
 		(!frontsector->heightsec || frontsector->heightsec->MoreFlags & SECF_IGNOREHEIGHTSEC))
 	{
@@ -179,6 +180,7 @@ void GLSceneDrawer::CheckViewArea(vertex_t *v1, vertex_t *v2, sector_t *frontsec
 		else
 			in_area = area_normal;
 	}
+	return area_default;
 }
 
 

src/gl/scene/gl_scene.cpp

@@ -133,7 +133,7 @@ void GLSceneDrawer::SetViewArea()
 	}
 	else
 	{
-		in_area = area_default;	// depends on exposed lower sectors
+		in_area = level.HasHeightSecs? area_default : area_normal;	// depends on exposed lower sectors, if map contains heightsecs.
 	}
 }
 

src/gl/scene/gl_scenedrawer.h

@@ -62,7 +62,7 @@ public:
 	void DrawEndScene2D(sector_t * viewsector);
 	void RenderActorsInPortal(FGLLinePortal *glport);
 
-	void CheckViewArea(vertex_t *v1, vertex_t *v2, sector_t *frontsector, sector_t *backsector);
+	area_t CheckViewArea(vertex_t *v1, vertex_t *v2, sector_t *frontsector, sector_t *backsector);
 
 	sector_t *RenderViewpoint(AActor * camera, GL_IRECT * bounds, float fov, float ratio, float fovratio, bool mainview, bool toscreen);
 	void RenderView(player_t *player);

src/p_spec.cpp

@@ -1361,6 +1361,7 @@ void P_SpawnSpecials (void)
 		case Transfer_Heights:
 			{
 				sec = line.frontsector;
+				
 				if (line.args[1] & 2)
 				{
 					sec->MoreFlags |= SECF_FAKEFLOORONLY;
@@ -1381,6 +1382,7 @@ void P_SpawnSpecials (void)
 				{
 					sec->MoreFlags |= SECF_IGNOREHEIGHTSEC;
 				}
+				else level.HasHeightSecs = true;
 				if (line.args[1] & 32)
 				{
 					sec->MoreFlags |= SECF_NOFAKELIGHT;