- render partial sprites oon the back side of a portal for actors in front of it. This is needed because the stencil will clip away those parts.

src/gl/data/gl_data.h

@@ -59,7 +59,8 @@ struct FGLLinePortal
 	// defines the complete span of this portal
 	vertex_t	*v1, *v2;	// vertices, from v1 to v2
 	DVector2 delta;		// precalculated v2 - v1 for side checking
-	FLinePortal *reference;	// one of the associated line portals, for retrieving translation info etc.
+	TArray<FLinePortal *> lines;
+	int validcount = 0;
 };
 
 extern TArray<FPortal *> portals;

src/gl/data/gl_portaldata.cpp

@@ -443,7 +443,12 @@ void gl_InitPortals()
 			tempindex[i] = glLinePortals.Size();
 			line_t *pSrcLine = linePortals[i].mOrigin;
 			line_t *pLine = linePortals[i].mDestination;
-			FGLLinePortal glport = { pLine->v1, pLine->v2, {0, 0}, &linePortals[i] };
+			FGLLinePortal glport;
+			
+			glport.v1 = pLine->v1;
+			glport.v2 = pLine->v2;
+			glport.delta = { 0, 0 };
+			glport.lines.Push(&linePortals[i]);
 			glLinePortals.Push(glport);
 
 			// We cannot do this grouping for non-linked portals because they can be changed at run time.
@@ -474,6 +479,7 @@ void gl_InitPortals()
 								tempindex[j] = tempindex[i];
 								if (pLine->v1 == pLine2->v2) glLinePortals[tempindex[i]].v1 = pLine2->v1;
 								else glLinePortals[tempindex[i]].v2 = pLine2->v2;
+								glLinePortals[tempindex[i]].lines.Push(&linePortals[j]);
 							}
 						}
 					}

src/gl/scene/gl_portal.cpp

@@ -102,7 +102,7 @@ UniqueList<GLHorizonInfo> UniqueHorizons;
 UniqueList<secplane_t> UniquePlaneMirrors;
 UniqueList<FGLLinePortal> UniqueLineToLines;
 
-
+void gl_RenderActorsInPortal(FGLLinePortal *glport);
 
 //==========================================================================
 //
@@ -1003,7 +1003,7 @@ void GLLineToLinePortal::DrawContents()
 
 	GLRenderer->mClipPortal = this;
 
-	line_t *origin = glport->reference->mOrigin;
+	line_t *origin = glport->lines[0]->mOrigin;
 	P_TranslatePortalXY(origin, ViewPos.X, ViewPos.Y);
 	P_TranslatePortalAngle(origin, ViewAngle);
 	P_TranslatePortalZ(origin, ViewPos.Z);
@@ -1038,17 +1038,22 @@ void GLLineToLinePortal::DrawContents()
 		currentmapsection[mapsection >> 3] |= 1 << (mapsection & 7);
 	}
 
-	GLRenderer->mViewActor = NULL;
+	GLRenderer->mViewActor = nullptr;
 	GLRenderer->SetupView(ViewPos.X, ViewPos.Y, ViewPos.Z, ViewAngle, !!(MirrorFlag&1), !!(PlaneMirrorFlag&1));
 
 	ClearClipper();
-	gl_RenderState.SetClipLine(glport->reference->mDestination);
+	gl_RenderState.SetClipLine(glport->lines[0]->mDestination);
 	gl_RenderState.EnableClipLine(true);
 	GLRenderer->DrawScene();
 	gl_RenderState.EnableClipLine(false);
 	RestoreMapSection();
 }
 
+void GLLineToLinePortal::RenderAttached()
+{
+	gl_RenderActorsInPortal(glport);
+}
+
 //-----------------------------------------------------------------------------
 //-----------------------------------------------------------------------------
 //

src/gl/scene/gl_portal.h

@@ -169,6 +169,7 @@ public:
 	virtual int ClipSubsector(subsector_t *sub) { return PClip_Inside; }
 	virtual int ClipPoint(const DVector2 &pos) { return PClip_Inside; }
 	virtual line_t *ClipLine() { return NULL; }
+	virtual void RenderAttached() {}
 
 	static void BeginScene();
 	static void StartFrame();
@@ -194,10 +195,10 @@ struct GLLinePortal : public GLPortal
 
 	GLLinePortal(FGLLinePortal *line)
 	{
-		if (line->reference->mType != PORTT_LINKED)
+		if (line->lines[0]->mType != PORTT_LINKED)
 		{
 			// For non-linked portals we must check the actual linedef.
-			line_t *lline = line->reference->mDestination;
+			line_t *lline = line->lines[0]->mDestination;
 			v1 = lline->v1;
 			v2 = lline->v2;
 		}
@@ -258,6 +259,7 @@ protected:
 	virtual void * GetSource() const { return glport; }
 	virtual const char *GetName();
 	virtual line_t *ClipLine() { return line(); }
+	virtual void RenderAttached();
 
 public:
 	

src/gl/scene/gl_scene.cpp

@@ -308,6 +308,7 @@ void FGLRenderer::CreateScene()
 	R_SetView();
 	validcount++;	// used for processing sidedefs only once by the renderer.
 	gl_RenderBSPNode (nodes + numnodes - 1);
+	if (GLRenderer->mCurrentPortal != NULL) GLRenderer->mCurrentPortal->RenderAttached();
 	Bsp.Unclock();
 
 	// And now the crappy hacks that have to be done to avoid rendering anomalies:

src/gl/scene/gl_sprite.cpp

@@ -521,7 +521,7 @@ void GLSprite::PerformSpriteClipAdjustment(AActor *thing, const DVector2 &thingp
 //
 //==========================================================================
 
-void GLSprite::Process(AActor* thing, sector_t * sector, bool thruportal)
+void GLSprite::Process(AActor* thing, sector_t * sector, int thruportal)
 {
 	sector_t rs;
 	sector_t * rendersector;
@@ -552,7 +552,7 @@ void GLSprite::Process(AActor* thing, sector_t * sector, bool thruportal)
 
 	// [RH] Interpolate the sprite's position to make it look smooth
 	DVector3 thingpos = thing->InterpolatedPosition(r_TicFracF);
-	if (thruportal) thingpos += Displacements.getOffset(thing->Sector->PortalGroup, sector->PortalGroup);
+	if (thruportal == 1) thingpos += Displacements.getOffset(thing->Sector->PortalGroup, sector->PortalGroup);
 
 	// Too close to the camera. This doesn't look good if it is a sprite.
 	if (fabs(thingpos.X - ViewPos.X) < 2 && fabs(thingpos.Y - ViewPos.Y) < 2)
@@ -581,7 +581,7 @@ void GLSprite::Process(AActor* thing, sector_t * sector, bool thruportal)
 		thing->flags7 |= MF7_FLYCHEAT;	// do this only once for the very first frame, but not if it gets into range again.
 	}
 
-	if (GLRenderer->mClipPortal)
+	if (thruportal != 2 && GLRenderer->mClipPortal)
 	{
 		int clipres = GLRenderer->mClipPortal->ClipPoint(thingpos);
 		if (clipres == GLPortal::PClip_InFront) return;
@@ -601,7 +601,6 @@ void GLSprite::Process(AActor* thing, sector_t * sector, bool thruportal)
 	topclip = rendersector->PortalBlocksMovement(sector_t::ceiling) ? LARGE_VALUE : rendersector->GetPortalPlaneZ(sector_t::ceiling);
 	bottomclip = rendersector->PortalBlocksMovement(sector_t::floor) ? -LARGE_VALUE : rendersector->GetPortalPlaneZ(sector_t::floor);
 
-
 	x = thingpos.X;
 	z = thingpos.Z - thing->Floorclip;
 	y = thingpos.Y;
@@ -1019,5 +1018,56 @@ void GLSprite::ProcessParticle (particle_t *particle, sector_t *sector)//, int s
 	rendered_sprites++;
 }
 
+//==========================================================================
+//
+// 
+//
+//==========================================================================
 
+void gl_RenderActorsInPortal(FGLLinePortal *glport)
+{
+	TMap<AActor*, bool> processcheck;
+	if (glport->validcount == validcount) return;	// only process once per frame
+	glport->validcount = validcount;
+	for (auto port : glport->lines)
+	{
+		line_t *line = port->mOrigin;
+		if (line->isLinePortal())	// only crossable ones
+		{
+			FLinePortal *port2 = port->mDestination->getPortal();
+			// process only if the other side links back to this one.
+			if (port2 != nullptr && port->mDestination == port2->mOrigin && port->mOrigin == port2->mDestination)
+			{
 
+				for (portnode_t *node = port->render_thinglist; node != nullptr; node = node->m_snext)
+				{
+					AActor *th = node->m_thing;
+
+					// process each actor only once per portal.
+					bool *check = processcheck.CheckKey(th);
+					if (check && *check) continue;
+					processcheck[th] = true;
+
+					DAngle savedangle = th->Angles.Yaw;
+					DVector3 savedpos = th->Pos();
+					DVector3 newpos = savedpos;
+					sector_t fakesector;
+
+					P_TranslatePortalXY(line, newpos.X, newpos.Y);
+					P_TranslatePortalZ(line, newpos.Z);
+					P_TranslatePortalAngle(line, th->Angles.Yaw);
+					th->SetXYZ(newpos);
+					th->Prev += newpos - savedpos;
+
+					GLSprite spr;
+					th->fillcolor = 0xff0000ff;
+					spr.Process(th, gl_FakeFlat(th->Sector, &fakesector, false), 2);
+					th->fillcolor = 0xffffffff;
+					th->Angles.Yaw = savedangle;
+					th->SetXYZ(savedpos);
+					th->Prev -= newpos - savedpos;
+				}
+			}
+		}
+	}
+}

src/gl/scene/gl_wall.h

@@ -359,7 +359,7 @@ public:
 
 	void Draw(int pass);
 	void PutSprite(bool translucent);
-	void Process(AActor* thing,sector_t * sector, bool thruportal = false);
+	void Process(AActor* thing,sector_t * sector, int thruportal = false);
 	void ProcessParticle (particle_t *particle, sector_t *sector);//, int shade, int fakeside)
 	void SetThingColor(PalEntry);