Revert "- restricted the portal rendering shortcut only to real skies in the primary layer."

This reverts commit b193e582ce.

This made the one thing I hoped it would fix even worse so it's useless.

src/rendering/hwrenderer/scene/hw_portal.cpp

@@ -126,13 +126,42 @@ bool FPortalSceneState::RenderFirstSkyPortal(int recursion, HWDrawInfo *outer_di
 	HWPortal * best = nullptr;
 	unsigned bestindex = 0;
 
-	if (recursion > 0 || outer_di->Portals.Size() != 1 || !outer_di->Portals[0]->IsSky()) return false;
+	// Find the one with the highest amount of lines.
+	// Normally this is also the one that saves the largest amount
+	// of time by drawing it before the scene itself.
+	auto &portals = outer_di->Portals;
+	for (int i = portals.Size() - 1; i >= 0; --i)
+	{
+		auto p = portals[i];
+		if (p->lines.Size() > 0 && p->IsSky())
+		{
+			// Cannot clear the depth buffer inside a portal recursion
+			if (recursion && p->NeedDepthBuffer()) continue;
 
-	best = outer_di->Portals[0];
-	outer_di->Portals.Clear();
-	RenderPortal(best, state, false, outer_di);
-	delete best;
-	return true;
+			if (!best || p->lines.Size() > best->lines.Size())
+			{
+				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;
+			}
+		}
+	}
+
+	if (best)
+	{
+		portals.Delete(bestindex);
+		RenderPortal(best, state, false, outer_di);
+		delete best;
+		return true;
+	}
+	return false;
 }
 
 

src/rendering/hwrenderer/scene/hw_portal.h

@@ -279,7 +279,7 @@ protected:
 	bool Setup(HWDrawInfo *di, FRenderState &rstate, Clipper *clipper) override;
 	void Shutdown(HWDrawInfo *di, FRenderState &rstate) override;
 	virtual void * GetSource() const { return origin; }
-	virtual bool IsSky() { return false; }
+	virtual bool IsSky() { return true; }	// although this isn't a real sky it can be handled as one.
 	virtual const char *GetName();
 	FSectorPortalGroup *origin;