Create VBO vertex data before the level mesh since the mesh uses it to build geometry.

Draw all sectors as subsectors if lightmaps are enabled (even if a sector doesn't have a tile initially it could gain one)

src/gamedata/r_defs.h

@@ -729,7 +729,6 @@ struct sector_t
 	int				vbocount[2];	// Total count of vertices belonging to this sector's planes. This is used when a sector height changes and also contains all attached planes.
 	int				ibocount;		// number of indices per plane (identical for all planes.) If this is -1 the index buffer is not in use.
 
-	bool HasLightmaps = false;		// Sector has lightmaps, each subsector vertex needs its own unique lightmap UV data
 	bool Sec3dControlUseMidTex = false;
 
 	// Below are all properties which are not used by the renderer.

src/maploader/maploader.cpp

@@ -2942,7 +2942,7 @@ void MapLoader::CalcIndices()
 //
 //==========================================================================
 
-void MapLoader::InitLevelMesh(MapData* map)
+void MapLoader::InitLightmapTiles(MapData* map)
 {
 	// Propagate sample distance where it isn't yet set
 	for (auto& line : Level->lines)
@@ -3017,7 +3017,10 @@ void MapLoader::InitLevelMesh(MapData* map)
 		subsector.LightmapTiles[1] = TArrayView<int>(&Level->LightmapTiles[offset + count], count);
 		offset += count * 2;
 	}
+}
 
+void MapLoader::InitLevelMesh(MapData* map)
+{
 	// Create the levelmesh
 	Level->levelMesh = new DoomLevelMesh(*Level);
 
@@ -3553,7 +3556,7 @@ void MapLoader::LoadLevel(MapData *map, const char *lumpname, int position)
 	if (!Level->IsReentering())
 		Level->FinalizePortals();	// finalize line portals after polyobjects have been initialized. This info is needed for properly flagging them.
 
-	InitLevelMesh(map);
+	InitLightmapTiles(map);
 
 	Level->ClearDynamic3DFloorData();	// CreateVBO must be run on the plain 3D floor data.
 	CreateVBO(*screen->RenderState(), Level->sectors);
@@ -3562,6 +3565,10 @@ void MapLoader::LoadLevel(MapData *map, const char *lumpname, int position)
 		P_Recalculate3DFloors(&sec);
 	}
 
+	InitLevelMesh(map);
+
+	UpdateVBOLightmap(*screen->RenderState(), Level->sectors);
+
 	Level->aabbTree = new DoomLevelAABBTree(Level);
 
 	// [DVR] Populate subsector->bbox for alternative space culling in orthographic projection with no fog of war

src/maploader/maploader.h

@@ -308,6 +308,7 @@ public:
 	void SetSlopes();
 	void CopySlopes();
 
+	void InitLightmapTiles(MapData* map);
 	void InitLevelMesh(MapData* map);
 	bool LoadLightmap(MapData* map);
 

src/rendering/hwrenderer/doom_levelmesh.cpp

@@ -1716,9 +1716,6 @@ void DoomLevelMesh::SetSubsectorLightmap(int surfaceIndex)
 	int lightmapTileIndex = Mesh.Surfaces[surfaceIndex].LightmapTileIndex;
 	auto surface = &DoomSurfaceInfos[surfaceIndex];
 
-	if (surface->Subsector->firstline && surface->Subsector->firstline->sidedef)
-		surface->Subsector->firstline->sidedef->sector->HasLightmaps = true;
-
 	if (!surface->ControlSector)
 	{
 		int index = surface->Type == ST_CEILING ? 1 : 0;

src/rendering/hwrenderer/hw_vertexbuilder.cpp

@@ -255,31 +255,12 @@ static int CreateIndexedSectorVerticesLM(sector_t* sec, const secplane_t& plane,
 		for(auto& sub : section.subsectors)
 		{
 			// vertices
-			int lightmap = sub->LightmapTiles[h].Size() > lightmapIndex ? sub->LightmapTiles[h][lightmapIndex] : -1;
-			if (lightmap >= 0) // tile may be missing if the subsector is degenerate triangle
+			for (unsigned int j = 0; j < sub->numlines; j++)
 			{
-				const auto& tile = level.levelMesh->Lightmap.Tiles[lightmap];
-				float textureSize = (float)level.levelMesh->Lightmap.TextureSize;
-				float lindex = (float)tile.AtlasLocation.ArrayIndex;
-				for (unsigned int j = 0, end = sub->numlines; j < end; j++)
-				{
-					vertex_t* vt = sub->firstline[j].v1;
-					FVector2 luv = tile.ToUV(FVector3((float)vt->fX(), (float)vt->fY(), (float)plane.ZatPoint(vt)), textureSize);
-					SetFlatVertex(vbo_shadowdata[vi + pos], vt, plane, luv.X, luv.Y, lindex);
-					vbo_shadowdata[vi + pos].z += diff;
-					vbo_origins[vi + pos] = SectorVertexOrigin(sub, h, lightmapIndex);
-					pos++;
-				}
-			}
-			else
-			{
-				for (unsigned int j = 0; j < sub->numlines; j++)
-				{
-					SetFlatVertex(vbo_shadowdata[vi + pos], sub->firstline[j].v1, plane);
-					vbo_shadowdata[vi + pos].z += diff;
-					vbo_origins[vi + pos] = SectorVertexOrigin(sub, h, lightmapIndex);
-					pos++;
-				}
+				SetFlatVertex(vbo_shadowdata[vi + pos], sub->firstline[j].v1, plane);
+				vbo_shadowdata[vi + pos].z += diff;
+				vbo_origins[vi + pos] = SectorVertexOrigin(sub, h, lightmapIndex);
+				pos++;
 			}
 		}
 	}
@@ -307,7 +288,7 @@ static int CreateIndexedSectorVerticesLM(sector_t* sec, const secplane_t& plane,
 
 static int CreateIndexedSectorVertices(sector_t* sec, const secplane_t& plane, int floor, VertexContainer& verts, int h, int lightmapIndex)
 {
-	if (sec->HasLightmaps && lightmapIndex != -1)
+	if (level.lightmaps && lightmapIndex != -1)
 		return CreateIndexedSectorVerticesLM(sec, plane, floor, h, lightmapIndex);
 
 	auto& vbo_shadowdata = sector_vertices;
@@ -568,6 +549,14 @@ void UpdateVBOLightmap(FRenderState& renderstate, sector_t* sector)
 	}
 }
 
+void UpdateVBOLightmap(FRenderState& renderstate, TArray<sector_t>& sectors)
+{
+	for (sector_t& sector : sectors)
+	{
+		UpdateVBOLightmap(renderstate, &sector);
+	}
+}
+
 //==========================================================================
 //
 //

src/rendering/hwrenderer/hw_vertexbuilder.h

@@ -72,6 +72,7 @@ VertexContainers BuildVertices(TArray<sector_t> &sectors);
 class FRenderState;
 void CheckUpdate(FRenderState& renderstate, sector_t* sector);
 void UpdateVBOLightmap(FRenderState& renderstate, sector_t* sector);
+void UpdateVBOLightmap(FRenderState& renderstate, TArray<sector_t>& sectors);
 void CreateVBO(FRenderState& renderstate, TArray<sector_t>& sectors);
 
 extern TArray<FFlatVertex> sector_vertices;