After this any old mesh has become invalid and needs to be rebuilt.

- use only one Section type.

source/core/rendering/hw_sections.cpp

@@ -46,6 +46,7 @@
 #include "nodebuilder/nodebuild.h"
 
 
+FMemArena tempsectionArena(102400);
 TArray<SectionLine> sectionLines;
 TArray<Section> Sections;
 TArray<TArray<int>> sectionspersector;	// reverse map, mainly for the automap
@@ -59,13 +60,15 @@ TArray<int> splits;
 void hw_BuildSections()
 {
 	Sections.Resize(numsectors);
+	memset(Sections.Data(), 0, numsectors * sizeof(Section));
 	sectionspersector.Resize(numsectors);
 	sectionLines.Resize(numwalls * 5 / 4); // cannot reallocate, unfortunately.
 	numsectionlines = numwalls;
 	for (int i = 0; i < numsectors; i++)
 	{
 		Sections[i].sector = i;
-		Sections[i].lines.Resize(sector[i].wallnum);
+		auto lines = (int*)tempsectionArena.Alloc(sector[i].wallnum * sizeof(int));
+		Sections[i].lines.Set(lines, sector[i].wallnum);
 		for (int j = 0; j < sector[i].wallnum; j++) Sections[i].lines[j] = sector[i].wallptr + j;
 		sectionspersector[i].Resize(1);
 		sectionspersector[i][0] = i;

source/core/rendering/hw_sections.h

@@ -2,6 +2,14 @@
 
 #include "build.h"
 
+enum ESEctionFlag
+{
+	Unclosed = 1,	// at least one unclosed loop
+	Dumped = 2,		// builder was unable to properly construct, so content may not be usable for triangulator.
+	BadWinding = 4,
+};
+
+
 struct SectionLine
 {
 	int section;
@@ -25,11 +33,21 @@ inline SectionLine* SectionLine::partnerLine() const
 	return partner == -1 ? nullptr : &sectionLines[partner];
 }
 
+struct Section2Loop
+{
+	TArrayView<int> walls;
+};
+
 struct Section
 {
+	uint8_t flags;
+	uint8_t dirty;
+	uint8_t geomflags;
+	unsigned index;
 	int sector;
-	// this is the whole point of sections - instead of just having a start index and count, we have an explicit list of lines that's a lot easier to change when needed.
-	TArray<int> lines;	
+	// this uses a memory arena for storage, so use TArrayView instead of TArray
+	TArrayView<int> lines;
+	TArrayView<Section2Loop> loops;
 };
 
 extern TArray<Section> Sections;

source/core/rendering/hw_sections2.cpp

@@ -43,12 +43,13 @@
 #include "memarena.h"
 #include "c_cvars.h"
 
+FMemArena sectionArena(102400);
+
 CVAR(Bool, hw_sectiondebug, false, 0)
 TMap<int, bool> bugged;
 
-static FMemArena sectionArena(102400);
-TArray<Section2*> sections2;
-TArrayView<TArrayView<Section2*>> sections2PerSector;
+TArray<Section*> sections2;
+TArrayView<TArrayView<Section*>> sections2PerSector;
 
 struct loopcollect
 {
@@ -548,9 +549,9 @@ static void ConstructSections(TArray<sectionbuildsector>& builders)
 		auto& builder = builders[i];
 		count += builder.sections.Size();
 
-		size = sizeof(Section2*) * builder.sections.Size();
+		size = sizeof(Section*) * builder.sections.Size();
 		data = sectionArena.Calloc(size);
-		sections2PerSector[i].Set(static_cast<Section2** >(data), builder.sections.Size()); // although this may need reallocation, it is too small to warrant single allocations for each sector.
+		sections2PerSector[i].Set(static_cast<Section** >(data), builder.sections.Size()); // although this may need reallocation, it is too small to warrant single allocations for each sector.
 	}
 	sections2.Resize(count); // this we cannot put into the arena because its size may change.
 	memset(sections2.Data(), 0, count * sizeof(*sections2.Data()));
@@ -563,7 +564,7 @@ static void ConstructSections(TArray<sectionbuildsector>& builders)
 		auto& builder = builders[i];
 		for (unsigned j = 0; j < builder.sections.Size(); j++)
 		{
-			auto section = (Section2*)sectionArena.Calloc(sizeof(Section2));
+			auto section = (Section*)sectionArena.Calloc(sizeof(Section));
 			auto& srcsect = builder.sections[j];
 			sections2[cursection] = section;
 			sections2PerSector[i][j] = section;
@@ -661,7 +662,7 @@ void hw_CreateSections2()
 //
 //==========================================================================
 
-Outline BuildOutline(Section2* section)
+Outline BuildOutline(Section* section)
 {
 	Outline output(section->loops.Size(), true);
 	for (unsigned i = 0; i < section->loops.Size(); i++)

source/core/rendering/hw_sections2.h

@@ -1,35 +1,10 @@
 #include "hw_sections.h"
-struct Section2;
 
-enum ESEctionFlag
-{
-	Unclosed = 1,	// at least one unclosed loop
-	Dumped = 2,		// builder was unable to properly construct, so content may not be usable for triangulator.
-	BadWinding = 4,
-};
-
-struct Section2Loop
-{
-	TArrayView<int> walls;
-};
-
-struct Section2
-{
-	uint8_t flags;
-	uint8_t dirty;
-	uint8_t geomflags;
-	unsigned index;
-	int sector;
-	// this uses a memory arena for storage, so use TArrayView instead of TArray
-	TArrayView<int> lines;
-	TArrayView<Section2Loop> loops;
-};
-
-extern TArray<Section2*> sections2;
-extern TArrayView<TArrayView<Section2*>> sections2PerSector;
+extern TArray<Section*> sections2;
+extern TArrayView<TArrayView<Section*>> sections2PerSector;
 
 void hw_CreateSections2();
 using Outline = TArray<TArray<vec2_t>>;
 using Point = std::pair<float, float>;
 using FOutline = std::vector<std::vector<Point>> ; // Data type was chosen so it can be passed directly into Earcut.
-Outline BuildOutline(Section2* section);
+Outline BuildOutline(Section* section);

source/core/rendering/scene/hw_drawstructs.h

@@ -31,7 +31,7 @@ class VSMatrix;
 struct FSpriteModelFrame;
 class FRenderState;
 struct voxmodel_t;
-struct Section2;
+struct Section;
 
 struct HWSectorPlane
 {
@@ -254,7 +254,7 @@ class HWFlat
 {
 public:
 	int oldsection;
-	Section2* section;
+	Section* section;
 	sectortype * sec;
 	tspritetype* Sprite; // for flat sprites.
 	FGameTexture *texture;
@@ -281,7 +281,7 @@ public:
 	//void SetupLights(HWDrawInfo *di, FLightNode *head, FDynLightData &lightdata, int portalgroup);
 
 	void PutFlat(HWDrawInfo* di, int whichplane);
-	void ProcessSector(HWDrawInfo *di, sectortype * frontsector, Section2* sectionp, int sectionnum, int which = 7 /*SSRF_RENDERALL*/);	// cannot use constant due to circular dependencies.
+	void ProcessSector(HWDrawInfo *di, sectortype * frontsector, Section* sectionp, int sectionnum, int which = 7 /*SSRF_RENDERALL*/);	// cannot use constant due to circular dependencies.
 	void ProcessFlatSprite(HWDrawInfo* di, tspritetype* sprite, sectortype* sector);
 	
 	void DrawSubsectors(HWDrawInfo *di, FRenderState &state);

source/core/rendering/scene/hw_flats.cpp

@@ -261,7 +261,7 @@ void HWFlat::PutFlat(HWDrawInfo *di, int whichplane)
 //
 //==========================================================================
 
-void HWFlat::ProcessSector(HWDrawInfo *di, sectortype * frontsector, Section2* sectionp, int section_, int which)
+void HWFlat::ProcessSector(HWDrawInfo *di, sectortype * frontsector, Section* sectionp, int section_, int which)
 {
 #ifdef _DEBUG
 	if (sectnum(sec) == gl_breaksec)

source/core/sectorgeometry.cpp

@@ -424,7 +424,7 @@ ETriangulateResult TriangulateOutlineNodeBuild(const FOutline& polygon, int coun
 //
 //==========================================================================
 
-bool SectionGeometry::ValidateSection(Section2* section, int plane)
+bool SectionGeometry::ValidateSection(Section* section, int plane)
 {
 	auto sec = &sector[section->sector];
 	auto& sdata = data[section->index];
@@ -469,7 +469,7 @@ bool SectionGeometry::ValidateSection(Section2* section, int plane)
 //
 //==========================================================================
 
-bool SectionGeometry::CreateMesh(Section2* section)
+bool SectionGeometry::CreateMesh(Section* section)
 {
 	auto outline = BuildOutline(section);
 	FOutline foutline;
@@ -508,7 +508,7 @@ bool SectionGeometry::CreateMesh(Section2* section)
 //
 //==========================================================================
 
-void SectionGeometry::CreatePlaneMesh(Section2* section, int plane, const FVector2& offset)
+void SectionGeometry::CreatePlaneMesh(Section* section, int plane, const FVector2& offset)
 {
 	auto sectorp = &sector[section->sector];
 	// calculate the rest.
@@ -559,7 +559,7 @@ void SectionGeometry::MarkDirty(sectortype* sector)
 //
 //==========================================================================
 
-SectionGeometryPlane* SectionGeometry::get(Section2* section, int plane, const FVector2& offset, TArray<int>** pIndices)
+SectionGeometryPlane* SectionGeometry::get(Section* section, int plane, const FVector2& offset, TArray<int>** pIndices)
 {
 	if (!section || section->index >= data.Size()) return nullptr;
 	auto sectp = &sector[section->sector];

source/core/sectorgeometry.h

@@ -4,7 +4,7 @@
 #include "vectors.h"
 #include "build.h"
 
-struct Section2;
+struct Section;
 
 struct SectorGeometryPlane
 {
@@ -73,14 +73,14 @@ class SectionGeometry
 {
 	TArray<SectionGeometryData> data;
 
-	bool ValidateSection(Section2* section, int plane);
+	bool ValidateSection(Section* section, int plane);
 	void MarkDirty(sectortype* sector);
-	bool CreateMesh(Section2* section);
-	void CreatePlaneMesh(Section2* section, int plane, const FVector2& offset);
+	bool CreateMesh(Section* section);
+	void CreatePlaneMesh(Section* section, int plane, const FVector2& offset);
 
 
 public:
-	SectionGeometryPlane* get(Section2* section, int plane, const FVector2& offset, TArray<int>** pIndices);
+	SectionGeometryPlane* get(Section* section, int plane, const FVector2& offset, TArray<int>** pIndices);
 
 	void SetSize(unsigned sectcount)
 	{