- moved the interpolator into FLevelLocals and refactored its use to happen outside the renderers.

There is no need to do this deep inside the renderer where it required code duplication and made it problematic to execute on multiple levels.
This is now being done before and after the top level call into the renderer in d_main.cpp.
This also serializes the interpolator itself to avoid problems with the Serialize functions adding the interpolations into the list which can only work with a single global instance.

src/d_main.cpp

@@ -754,9 +754,15 @@ void D_Display ()
 				Level->HasDynamicLights = !!level.lights;
 			}
 			else Level->HasDynamicLights = false;	// lights are off so effectively we have none.
+			Level->interpolator.DoInterpolations(I_GetTimeFrac());
 		}
-		
 		viewsec = screen->RenderView(&players[consoleplayer]);
+
+		for (auto Level : AllLevels())
+		{
+			Level->interpolator.RestoreInterpolations();
+		}
+
 		screen->Begin2D();
 		screen->DrawBlend(viewsec);
 		if (automapactive)

src/dobjgc.cpp

@@ -331,7 +331,6 @@ static void MarkRoot()
 		SectorMarker->SecNum = 0;
 	}
 	Mark(SectorMarker);
-	Mark(interpolator.Head);
 	// Mark bot stuff.
 	Mark(bglobal.firstthing);
 	Mark(bglobal.body1);

src/g_level.cpp

@@ -1983,6 +1983,7 @@ void FLevelLocals::Mark()
 	GC::Mark(FraggleScriptThinker);
 	GC::Mark(ACSThinker);
 	GC::Mark(automap);
+	GC::Mark(interpolator.Head);
 	canvasTextureInfo.Mark();
 	for (auto &c : CorpseQueue)
 	{

src/g_levellocals.h

@@ -50,6 +50,7 @@
 #include "p_destructible.h"
 #include "r_data/r_sections.h"
 #include "r_data/r_canvastexture.h"
+#include "r_data/r_interpolate.h"
 
 //============================================================================
 //
@@ -442,6 +443,7 @@ public:
 	FString		F1Pic;
 	EMapType	maptype;
 	FTagManager tagManager;
+	FInterpolator interpolator;
 
 	uint64_t	ShaderStartTime = 0;	// tell the shader system when we started the level (forces a timer restart)
 

src/gl/renderer/gl_scene.cpp

@@ -218,7 +218,6 @@ sector_t * FGLRenderer::RenderViewpoint (FRenderViewpoint &mainvp, AActor * came
 			mBuffers->BlitToEyeTexture(eye_ix);
 	}
 
-	interpolator.RestoreInterpolations ();
 	return mainvp.sector;
 }
 

src/p_saveg.cpp

@@ -962,9 +962,10 @@ void FLevelLocals::Serialize(FSerializer &arc, bool hubload)
 		("spotstate", SpotState)
 		("fragglethinker", FraggleScriptThinker)
 		("acsthinker", ACSThinker)
-        ("impactdecalcount", ImpactDecalCount)
+		("impactdecalcount", ImpactDecalCount)
 		("scrolls", Scrolls)
-		("automap", automap);
+		("automap", automap)
+		("interpolator", interpolator);
 
 
 	// Hub transitions must keep the current total time

src/p_setup.cpp

@@ -288,6 +288,7 @@ void FLevelLocals::ClearLevelData()
 	}
 	ClearPortals();
 
+	interpolator.ClearInterpolations();	// [RH] Nothing to interpolate on a fresh level.
 	tagManager.Clear();
 	ClearTIDHashes();
 	Behaviors.UnloadModules();
@@ -350,7 +351,6 @@ void P_FreeLevelData ()
 	R_FreePastViewers();
 	P_ClearUDMFKeys();
 
-	interpolator.ClearInterpolations();	// [RH] Nothing to interpolate on a fresh level.
 	SN_StopAllSequences ();
 	DThinker::DestroyAllThinkers ();
 

src/p_tick.cpp

@@ -75,7 +75,10 @@ void P_Ticker (void)
 {
 	int i;
 
-	interpolator.UpdateInterpolations ();
+	for (auto Level : AllLevels())
+	{
+		Level->interpolator.UpdateInterpolations();
+	}
 	r_NoInterpolate = true;
 
 	if (!demoplayback)

src/polyrenderer/poly_renderer.cpp

@@ -188,7 +188,6 @@ void PolyRenderer::RenderActorView(AActor *actor, bool dontmaplines)
 
 	if (Viewpoint.camera)
 		Viewpoint.camera->renderflags = savedflags;
-	interpolator.RestoreInterpolations ();
 	
 	NetUpdate();
 }

src/r_data/r_interpolate.cpp

@@ -39,6 +39,7 @@
 #include "p_local.h"
 #include "po_man.h"
 #include "serializer.h"
+#include "g_levellocals.h"
 
 //==========================================================================
 //
@@ -312,6 +313,16 @@ void FInterpolator::ClearInterpolations()
 	}
 }
 
+FSerializer &Serialize(FSerializer &arc, const char *key, FInterpolator &rs, FInterpolator *def)
+{
+	if (arc.BeginObject(key))
+	{
+		arc("head", rs.Head)
+			("count", rs.count)
+			.EndObject();
+	}
+	return arc;
+}
 
 //==========================================================================
 //
@@ -379,10 +390,6 @@ void DInterpolation::Serialize(FSerializer &arc)
 {
 	Super::Serialize(arc);
 	arc("refcount", refcount);
-	if (arc.isReading())
-	{
-		interpolator.AddInterpolation(this);
-	}
 }
 
 //==========================================================================
@@ -408,7 +415,7 @@ DSectorPlaneInterpolation::DSectorPlaneInterpolation(sector_t *_sector, bool _pl
 		P_Start3dMidtexInterpolations(attached, sector, ceiling);
 		P_StartLinkedSectorInterpolations(attached, sector, ceiling);
 	}
-	interpolator.AddInterpolation(this);
+	sector->Level->interpolator.AddInterpolation(this);
 }
 
 //==========================================================================
@@ -567,7 +574,7 @@ DSectorScrollInterpolation::DSectorScrollInterpolation(sector_t *_sector, bool _
 	sector = _sector;
 	ceiling = _plane;
 	UpdateInterpolation ();
-	interpolator.AddInterpolation(this);
+	sector->Level->interpolator.AddInterpolation(this);
 }
 
 //==========================================================================
@@ -672,7 +679,7 @@ DWallScrollInterpolation::DWallScrollInterpolation(side_t *_side, int _part)
 	side = _side;
 	part = _part;
 	UpdateInterpolation ();
-	interpolator.AddInterpolation(this);
+	side->GetLevel()->interpolator.AddInterpolation(this);
 }
 
 //==========================================================================
@@ -770,7 +777,7 @@ DPolyobjInterpolation::DPolyobjInterpolation(FPolyObj *po)
 	oldverts.Resize(po->Vertices.Size() << 1);
 	bakverts.Resize(po->Vertices.Size() << 1);
 	UpdateInterpolation ();
-	interpolator.AddInterpolation(this);
+	po->Level->interpolator.AddInterpolation(this);
 }
 
 //==========================================================================

src/r_data/r_interpolate.h

@@ -43,19 +43,13 @@ public:
 
 struct FInterpolator
 {
-	TObjPtr<DInterpolation*> Head;
-	bool didInterp;
-	int count;
+	TObjPtr<DInterpolation*> Head = nullptr;
+	bool didInterp = false;
+	int count = 0;
 
 	int CountInterpolations ();
 
 public:
-	FInterpolator()
-	{
-		Head = nullptr;
-		didInterp = false;
-		count = 0;
-	}
 	void UpdateInterpolations();
 	void AddInterpolation(DInterpolation *);
 	void RemoveInterpolation(DInterpolation *);
@@ -64,9 +58,6 @@ public:
 	void ClearInterpolations();
 };
 
-extern FInterpolator interpolator;
-
-
 
 #endif
 

src/r_utility.cpp

@@ -854,8 +854,6 @@ void R_SetupFrame (FRenderViewpoint &viewpoint, FViewWindow &viewwindow, AActor
 
 	viewpoint.SetViewAngle (viewwindow);
 
-	interpolator.DoInterpolations (viewpoint.TicFrac);
-
 	// Keep the view within the sector's floor and ceiling
 	if (viewpoint.sector->PortalBlocksMovement(sector_t::ceiling))
 	{

src/serializer.h

@@ -24,6 +24,7 @@ struct FDoorAnimation;
 class FSoundID;
 struct FPolyObj;
 union FRenderStyle;
+struct FInterpolator;
 
 inline bool nullcmp(const void *buffer, size_t length)
 {
@@ -202,6 +203,7 @@ FSerializer &Serialize(FSerializer &arc, const char *key, FString &sid, FString
 FSerializer &Serialize(FSerializer &arc, const char *key, NumericValue &sid, NumericValue *def);
 FSerializer &Serialize(FSerializer &arc, const char *key, ticcmd_t &sid, ticcmd_t *def);
 FSerializer &Serialize(FSerializer &arc, const char *key, usercmd_t &cmd, usercmd_t *def);
+FSerializer &Serialize(FSerializer &arc, const char *key, FInterpolator &rs, FInterpolator *def);
 
 template<class T>
 FSerializer &Serialize(FSerializer &arc, const char *key, T *&value, T **)

src/swrenderer/scene/r_scene.cpp

@@ -189,7 +189,6 @@ namespace swrenderer
 		RenderPSprites();
 
 		MainThread()->Viewport->viewpoint.camera->renderflags = savedflags;
-		interpolator.RestoreInterpolations();
 	}
 
 	void RenderScene::RenderPSprites()