From 2c4ac886aa0f71fd30d3ae13a7c826299a6cea8a Mon Sep 17 00:00:00 2001
From: "Dileep V. Reddy" <dileepvr@gmail.com>
Date: Mon, 17 Feb 2025 19:23:26 -0700
Subject: [PATCH] Stacked sector portals now render for OoB viewpoints.

---
 src/rendering/hwrenderer/scene/hw_portal.cpp | 27 +++++++++++++++++++-
 src/rendering/hwrenderer/scene/hw_portal.h   |  1 +
 src/rendering/hwrenderer/scene/hw_sky.cpp    |  7 +++--
 3 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/src/rendering/hwrenderer/scene/hw_portal.cpp b/src/rendering/hwrenderer/scene/hw_portal.cpp
index 01ab23b8a..7746aa338 100644
--- a/src/rendering/hwrenderer/scene/hw_portal.cpp
+++ b/src/rendering/hwrenderer/scene/hw_portal.cpp
@@ -805,10 +805,18 @@ bool HWSectorStackPortal::Setup(HWDrawInfo *di, FRenderState &rstate, Clipper *c
 	vp.Pos += origin->mDisplacement;
 	vp.ActorPos += origin->mDisplacement;
 	vp.ViewActor = nullptr;
+	vp.OffPos += origin->mDisplacement;
 
 	// avoid recursions!
 	if (origin->plane != -1) screen->instack[origin->plane]++;
-
+	if (lines.Size() > 0)
+	{
+		flat.plane.GetFromSector(lines[0].sub->sector,
+								 lines[0].sub->sector->GetPortal(sector_t::ceiling)->mType & (PORTS_STACKEDSECTORTHING | PORTS_PORTAL | PORTS_LINKEDPORTAL) ?
+								 sector_t::ceiling : sector_t::floor);
+		di->SetClipHeight(flat.plane.plane.ZatPoint(vp.Pos),
+						  flat.plane.plane.Normal().Z > 0 ? -1.f : 1.f);
+	}
 	di->SetupView(rstate, vp.Pos.X, vp.Pos.Y, vp.Pos.Z, !!(state->MirrorFlag & 1), !!(state->PlaneMirrorFlag & 1));
 	SetupCoverage(di);
 	ClearClipper(di, clipper);
@@ -816,6 +824,7 @@ bool HWSectorStackPortal::Setup(HWDrawInfo *di, FRenderState &rstate, Clipper *c
 	// If the viewpoint is not within the portal, we need to invalidate the entire clip area.
 	// The portal will re-validate the necessary parts when its subsectors get traversed.
 	subsector_t *sub = di->Level->PointInRenderSubsector(vp.Pos);
+	if (vp.IsAllowedOoB()) sub = di->Level->PointInRenderSubsector(vp.OffPos);
 	if (!(di->ss_renderflags[sub->Index()] & SSRF_SEEN))
 	{
 		clipper->SafeAddClipRange(0, ANGLE_MAX);
@@ -825,6 +834,22 @@ bool HWSectorStackPortal::Setup(HWDrawInfo *di, FRenderState &rstate, Clipper *c
 }
 
 
+void HWSectorStackPortal::DrawPortalStencil(FRenderState &state, int pass)
+{
+	bool isceiling = planesused & (1 << sector_t::ceiling);
+	for (unsigned int i = 0; i < lines.Size(); i++)
+	{
+		flat.section = lines[i].sub->section;
+		flat.iboindex = lines[i].sub->sector->iboindex[isceiling ? sector_t::ceiling : sector_t::floor];
+		flat.plane.GetFromSector(lines[i].sub->sector, isceiling ? sector_t::ceiling : sector_t::floor);
+		// if (isceiling) flat.plane.plane.FlipVert(); // Doesn't do anything. Stencil is a screen-space projection
+
+		state.SetNormal(flat.plane.plane.Normal().X, flat.plane.plane.Normal().Z, flat.plane.plane.Normal().Y);
+		state.DrawIndexed(DT_Triangles, flat.iboindex + flat.section->vertexindex, flat.section->vertexcount, i == 0);
+	}
+}
+
+
 void HWSectorStackPortal::Shutdown(HWDrawInfo *di, FRenderState &rstate)
 {
 	if (origin->plane != -1) screen->instack[origin->plane]--;
diff --git a/src/rendering/hwrenderer/scene/hw_portal.h b/src/rendering/hwrenderer/scene/hw_portal.h
index ab9fec945..50034df6a 100644
--- a/src/rendering/hwrenderer/scene/hw_portal.h
+++ b/src/rendering/hwrenderer/scene/hw_portal.h
@@ -270,6 +270,7 @@ struct HWSectorStackPortal : public HWScenePortalBase
 	TArray<subsector_t *> subsectors;
 protected:
 	bool Setup(HWDrawInfo *di, FRenderState &rstate, Clipper *clipper) override;
+	void DrawPortalStencil(FRenderState &state, int pass) override;
 	void Shutdown(HWDrawInfo *di, FRenderState &rstate) override;
 	virtual void * GetSource() const { return origin; }
 	virtual bool IsSky() { return true; }	// although this isn't a real sky it can be handled as one.
diff --git a/src/rendering/hwrenderer/scene/hw_sky.cpp b/src/rendering/hwrenderer/scene/hw_sky.cpp
index 4610f00da..b39df6695 100644
--- a/src/rendering/hwrenderer/scene/hw_sky.cpp
+++ b/src/rendering/hwrenderer/scene/hw_sky.cpp
@@ -154,12 +154,15 @@ void HWWall::SkyPlane(HWWallDispatcher *di, sector_t *sector, int plane, bool al
 		case PORTS_PORTAL:
 		case PORTS_LINKEDPORTAL:
 		{
-			if (di->di && di->di->Viewpoint.IsAllowedOoB()) return; // Almost works (with planemirrorportal stencil), but no quite
+			if (di->di && di->di->Viewpoint.IsAllowedOoB())
+			{
+				secplane_t myplane = plane ? sector->ceilingplane : sector->floorplane;
+				if (di->di->Viewpoint.ViewVector3D.dot(myplane.Normal()) > 0.0) return;
+			}
 			auto glport = sector->GetPortalGroup(plane);
 			if (glport != NULL)
 			{
 				if (sector->PortalBlocksView(plane)) return;
-
 				if (di->di && screen->instack[1 - plane]) return;
 				ptype = PORTALTYPE_SECTORSTACK;
 				portal = glport;