- changed the stencil cap drawer to only cover the area which is actually used by the portal.

This will now both exclude floor caps when only ceiling elements are used and everything outside the bounding box of active portal lines.
Hopefully this is enough to fix the issues with portal caps but of course it is not foolproof if someone just makes the right setup.

src/hwrenderer/scene/hw_drawstructs.h

@@ -201,7 +201,7 @@ public:
 //private:
 
 	void PutWall(HWDrawInfo *di, bool translucent);
-	void PutPortal(HWDrawInfo *di, int ptype);
+	void PutPortal(HWDrawInfo *di, int ptype, int plane);
 	void CheckTexturePosition(FTexCoordInfo *tci);
 
 	void Put3DWall(HWDrawInfo *di, lightlist_t * lightlist, bool translucent);

src/hwrenderer/scene/hw_portal.cpp

@@ -140,6 +140,14 @@ bool FPortalSceneState::RenderFirstSkyPortal(int recursion, HWDrawInfo *outer_di
 				best = p;
 				bestindex = i;
 			}
+
+			// If the portal area contains the current camera viewpoint, let's always use it because it's likely to give the largest area.
+			if (p->boundingBox.contains(outer_di->Viewpoint.Pos))
+			{
+				best = p;
+				bestindex = i;
+				break;
+			}
 		}
 	}
 
@@ -187,8 +195,27 @@ void HWPortal::DrawPortalStencil(FRenderState &state, int pass)
 	{
 		// The cap's depth handling needs special treatment so that it won't block further portal caps.
 		if (pass == STP_DepthRestore) state.SetDepthRange(1, 1);
-		state.Draw(DT_TriangleFan, FFlatVertexBuffer::STENCILTOP_INDEX, 4, false);
+
-		state.Draw(DT_TriangleFan, FFlatVertexBuffer::STENCILBOTTOM_INDEX, 4, false);
+		if (planesused & (1 << sector_t::floor))
+		{
+			auto verts = screen->mVertexData->AllocVertices(4);
+			auto ptr = verts.first;
+			ptr[0].Set((float)boundingBox.left, -32767.f, (float)boundingBox.top, 0, 0);
+			ptr[1].Set((float)boundingBox.right, -32767.f, (float)boundingBox.top, 0, 0);
+			ptr[2].Set((float)boundingBox.left, -32767.f, (float)boundingBox.bottom, 0, 0);
+			ptr[3].Set((float)boundingBox.right, -32767.f, (float)boundingBox.bottom, 0, 0);
+			state.Draw(DT_TriangleStrip, verts.second, 4, false);
+		}
+		if (planesused & (1 << sector_t::ceiling))
+		{
+			auto verts = screen->mVertexData->AllocVertices(4);
+			auto ptr = verts.first;
+			ptr[0].Set((float)boundingBox.left, 32767.f, (float)boundingBox.top, 0, 0);
+			ptr[1].Set((float)boundingBox.right, 32767.f, (float)boundingBox.top, 0, 0);
+			ptr[2].Set((float)boundingBox.left, 32767.f, (float)boundingBox.bottom, 0, 0);
+			ptr[3].Set((float)boundingBox.right, 32767.f, (float)boundingBox.bottom, 0, 0);
+			state.Draw(DT_TriangleStrip, verts.second, 4, false);
+		}
 		if (pass == STP_DepthRestore) state.SetDepthRange(0, 1);
 	}
 }

src/hwrenderer/scene/hw_portal.h

@@ -61,8 +61,10 @@ class HWPortal
 public:
 	FPortalSceneState * mState;
 	TArray<GLWall> lines;
+	BoundingRect boundingBox;
+	int planesused = 0;
 
-    HWPortal(FPortalSceneState *s, bool local = false) : mState(s)
+    HWPortal(FPortalSceneState *s, bool local = false) : mState(s), boundingBox(false)
     {
     }
     virtual ~HWPortal() {}
@@ -83,6 +85,8 @@ public:
 	void AddLine(GLWall * l)
 	{
 		lines.Push(*l);
+		boundingBox.addVertex(l->glseg.x1, l->glseg.y1);
+		boundingBox.addVertex(l->glseg.x2, l->glseg.y2);
 	}
 
 

src/hwrenderer/scene/hw_sky.cpp

@@ -122,7 +122,7 @@ void GLWall::SkyPlane(HWDrawInfo *di, sector_t *sector, int plane, bool allowref
 		skyinfo.init(sector->sky, Colormap.FadeColor);
 		ptype = PORTALTYPE_SKY;
 		sky = &skyinfo;
-		PutPortal(di, ptype);
+		PutPortal(di, ptype, plane);
 	}
 	else if (sportal != nullptr)
 	{
@@ -162,7 +162,7 @@ void GLWall::SkyPlane(HWDrawInfo *di, sector_t *sector, int plane, bool allowref
 	}
 	if (ptype != -1)
 	{
-		PutPortal(di, ptype);
+		PutPortal(di, ptype, plane);
 	}
 }
 
@@ -197,7 +197,7 @@ void GLWall::SkyLine(HWDrawInfo *di, sector_t *fs, line_t *line)
 	ztop[1] = zceil[1];
 	zbottom[0] = zfloor[0];
 	zbottom[1] = zfloor[1];
-	PutPortal(di, ptype);
+	PutPortal(di, ptype, -1);
 }
 
 

src/hwrenderer/scene/hw_walls.cpp

@@ -483,10 +483,10 @@ void GLWall::PutWall(HWDrawInfo *di, bool translucent)
 //
 //==========================================================================
 
-void GLWall::PutPortal(HWDrawInfo *di, int ptype)
+void GLWall::PutPortal(HWDrawInfo *di, int ptype, int plane)
 {
 	auto pstate = screen->mPortalState;
-	HWPortal * portal;
+	HWPortal * portal = nullptr;
 
 	MakeVertices(di, false);
 	switch (ptype)
@@ -532,7 +532,6 @@ void GLWall::PutPortal(HWDrawInfo *di, int ptype)
 	case PORTALTYPE_PLANEMIRROR:
 		if (pstate->PlaneMirrorMode * planemirror->fC() <= 0)
 		{
-			//@sync-portal
 			planemirror = pstate->UniquePlaneMirrors.Get(planemirror);
 			portal = di->FindPortal(planemirror);
 			if (!portal)
@@ -588,6 +587,11 @@ void GLWall::PutPortal(HWDrawInfo *di, int ptype)
 		break;
 	}
 	vertcount = 0;
+
+	if (plane != -1 && portal)
+	{
+		portal->planesused |= (1<<plane);
+	}
 }
 
 //==========================================================================
@@ -849,7 +853,7 @@ bool GLWall::DoHorizon(HWDrawInfo *di, seg_t * seg,sector_t * fs, vertex_t * v1,
 
 			if (di->isFullbrightScene()) hi.colormap.Clear();
 			horizon = &hi;
-			PutPortal(di, PORTALTYPE_HORIZON);
+			PutPortal(di, PORTALTYPE_HORIZON, -1);
 		}
 		ztop[1] = ztop[0] = zbottom[0];
 	} 
@@ -878,7 +882,7 @@ bool GLWall::DoHorizon(HWDrawInfo *di, seg_t * seg,sector_t * fs, vertex_t * v1,
 
 			if (di->isFullbrightScene()) hi.colormap.Clear();
 			horizon = &hi;
-			PutPortal(di, PORTALTYPE_HORIZON);
+			PutPortal(di, PORTALTYPE_HORIZON, -1);
 		}
 	}
 	return true;
@@ -1135,7 +1139,7 @@ void GLWall::DoTexture(HWDrawInfo *di, int _type,seg_t * seg, int peg,
 
 	if (seg->linedef->special == Line_Mirror && _type == RENDERWALL_M1S && gl_mirrors)
 	{
-		PutPortal(di, PORTALTYPE_MIRROR);
+		PutPortal(di, PORTALTYPE_MIRROR, -1);
 	}
 	else
 	{
@@ -1970,7 +1974,7 @@ void GLWall::Process(HWDrawInfo *di, seg_t *seg, sector_t * frontsector, sector_
 			ztop[1] = zceil[1];
 			zbottom[0] = zfloor[0];
 			zbottom[1] = zfloor[1];
-			PutPortal(di, PORTALTYPE_LINETOLINE);
+			PutPortal(di, PORTALTYPE_LINETOLINE, -1);
 		}
 		else if (seg->linedef->GetTransferredPortal())
 		{
@@ -2077,7 +2081,7 @@ void GLWall::Process(HWDrawInfo *di, seg_t *seg, sector_t * frontsector, sector_
 			ztop[1] = bch2;
 			zbottom[0] = bfh1;
 			zbottom[1] = bfh2;
-			PutPortal(di, PORTALTYPE_LINETOLINE);
+			PutPortal(di, PORTALTYPE_LINETOLINE, -1);
 		}
 		else if (backsector->e->XFloor.ffloors.Size() || frontsector->e->XFloor.ffloors.Size())
 		{

src/r_data/r_sections.cpp

@@ -495,9 +495,9 @@ public:
 			auto &section = sections[i];
 			auto &work = triangles[i];
 
-			BoundingRect bounds = { 1e32, 1e32, -1e32, -1e32 };
+			BoundingRect bounds(false);
-			BoundingRect loopBounds = { 1e32, 1e32, -1e32, -1e32 };
+			BoundingRect loopBounds(false);
-			BoundingRect outermostBounds = { 1e32, 1e32, -1e32, -1e32 };
+			BoundingRect outermostBounds(false);
 			unsigned outermoststart = ~0u;
 			unsigned loopstart = 0;
 			bool ispolyorg = false;
@@ -519,7 +519,7 @@ public:
 						outermoststart = loopstart;
 						loopstart = i + 1;
 					}
-					loopBounds = { 1e32, 1e32, -1e32, -1e32 };
+					loopBounds.setEmpty();
 				}
 			}
 			work.boundingLoopStart = outermoststart;
@@ -716,7 +716,7 @@ public:
 			dest.subsectors.Set(&output.allSubsectors[numsubsectors], group.subsectors.Size());
 			dest.vertexindex = -1;
 			dest.vertexcount = 0;
-			dest.bounds = {1e32, 1e32, -1e32, -1e32};
+			dest.bounds.setEmpty();
 			numsegments += group.segments.Size();
 
 			if (output.firstSectionForSectorPtr[dest.sector->Index()] == -1)

src/r_data/r_sections.h

@@ -25,12 +25,35 @@ struct BoundingRect
 {
 	double left, top, right, bottom;
 
-	bool contains(const BoundingRect & other)
+	BoundingRect() = default;
+	BoundingRect(bool)
+	{
+		setEmpty();
+	}
+
+	void setEmpty()
+	{
+		left = top = 1e38;
+		bottom = right = -1e38;
+	}
+
+	bool contains(const BoundingRect & other) const
 	{
 		return left <= other.left && top <= other.top && right >= other.right && bottom >= other.bottom;
 	}
 
-	bool intersects(const BoundingRect & other)
+	bool contains(double x, double y) const
+	{
+		return left <= x && top <= y && right >= x && bottom >= y;
+	}
+
+	template <class T>
+	bool contains(const T &vec) const
+	{
+		return left <= vec.X && top <= vec.Y && right >= vec.X && bottom >= vec.Y;
+	}
+
+	bool intersects(const BoundingRect & other) const
 	{
 		return !(other.left > right ||
 			other.right < left ||
@@ -46,7 +69,7 @@ struct BoundingRect
 		if (other.bottom > bottom) bottom = other.bottom;
 	}
 
-	double distanceTo(const BoundingRect &other)
+	double distanceTo(const BoundingRect &other) const
 	{
 		if (intersects(other)) return 0;
 		return std::max(std::min(fabs(left - other.right), fabs(right - other.left)),
@@ -61,10 +84,11 @@ struct BoundingRect
 		if (y > bottom) bottom = y;
 	}
 
-	bool operator == (const BoundingRect &other)
+	bool operator == (const BoundingRect &other) const
 	{
 		return left == other.left && top == other.top && right == other.right && bottom == other.bottom;
 	}
+
 };