- made GLWall ready for multithreaded processing.

* to do this efficiently the amount of required vertices needs to be calculated up-front
* always create the vertices in the data generation pass, not the render pass.
* added synchronisation code to the vertex buffer allocator.

Without multithreading this causes a slight slowdown, due to added processing cost. (Frozen Time bridge scene drops from 47 fps to 44 fps on my test machine.

src/gl/data/gl_vertexbuffer.h

@@ -23,6 +23,9 @@
 #ifndef __VERTEXBUFFER_H
 #define __VERTEXBUFFER_H
 
+#include <atomic>
+#include <thread>
+#include <mutex>
 #include "tarray.h"
 #include "hwrenderer/utility/hw_clock.h"
 #include "gl/system/gl_interface.h"
@@ -93,7 +96,8 @@ class FFlatVertexBuffer : public FVertexBuffer, public FFlatVertexGenerator
 {
 	FFlatVertex *map;
 	unsigned int mIndex;
-	unsigned int mCurIndex;
+	std::atomic<unsigned int> mCurIndex;
+	std::mutex mBufferMutex;
 	unsigned int mNumReserved;
 
 
@@ -125,12 +129,22 @@ public:
 	{
 		return &map[mCurIndex];
 	}
-	FFlatVertex *Alloc(int num, int *poffset)
+
+	template<class T>
+	FFlatVertex *Alloc(int num, T *poffset)
 	{
+	again:
 		FFlatVertex *p = GetBuffer();
-		*poffset = mCurIndex;
-		mCurIndex += num;
-		if (mCurIndex >= BUFFER_SIZE_TO_USE) mCurIndex = mIndex;
+		auto index = mCurIndex.fetch_add(num);
+		*poffset = static_cast<T>(index);
+		if (index + num >= BUFFER_SIZE_TO_USE)
+		{
+			std::lock_guard<std::mutex> lock(mBufferMutex);
+			if (mCurIndex >= BUFFER_SIZE_TO_USE)	// retest condition, in case another thread got here first
+				mCurIndex = mIndex;
+
+			if (index >= BUFFER_SIZE_TO_USE) goto again;
+		}
 		return p;
 	}
 

src/gl/scene/gl_drawinfo.cpp

@@ -462,11 +462,8 @@ void GLDrawList::SortWallIntoWall(SortNode * head,SortNode * sort)
 		w->ztop[0]=ws->ztop[1]=izt;
 		w->zbottom[0]=ws->zbottom[1]=izb;
 		w->tcs[GLWall::LOLFT].u = w->tcs[GLWall::UPLFT].u = ws->tcs[GLWall::LORGT].u = ws->tcs[GLWall::UPRGT].u = iu;
-		if (gl.buffermethod == BM_DEFERRED)
-		{
-			ws->MakeVertices(false);
-			w->MakeVertices(false);
-		}
+		ws->MakeVertices(false);
+		w->MakeVertices(false);
 
 		SortNode * sort2=SortNodes.GetNew();
 		memset(sort2,0,sizeof(SortNode));

src/gl/scene/gl_portal.cpp

@@ -134,7 +134,6 @@ void GLPortal::DrawPortalStencil()
 
 		for (unsigned int i = 0; i < lines.Size(); i++)
 		{
-			if (gl.buffermethod != BM_DEFERRED) lines[i].MakeVertices(false);
 			mPrimIndices[i * 2] = lines[i].vertindex;
 			mPrimIndices[i * 2 + 1] = lines[i].vertcount;
 		}

src/gl/scene/gl_vertex.cpp

@@ -35,8 +35,6 @@ EXTERN_CVAR(Bool, gl_seamless)
 
 void GLWall::SplitUpperEdge(FFlatVertex *&ptr)
 {
-	if (seg == NULL || seg->sidedef == NULL || (seg->sidedef->Flags & WALLF_POLYOBJ) || seg->sidedef->numsegs == 1) return;
-
 	side_t *sidedef = seg->sidedef;
 	float polyw = glseg.fracright - glseg.fracleft;
 	float facu = (tcs[UPRGT].u - tcs[UPLFT].u) / polyw;
@@ -71,8 +69,6 @@ void GLWall::SplitUpperEdge(FFlatVertex *&ptr)
 
 void GLWall::SplitLowerEdge(FFlatVertex *&ptr)
 {
-	if (seg == NULL || seg->sidedef == NULL || (seg->sidedef->Flags & WALLF_POLYOBJ) || seg->sidedef->numsegs == 1) return;
-
 	side_t *sidedef = seg->sidedef;
 	float polyw = glseg.fracright - glseg.fracleft;
 	float facu = (tcs[LORGT].u - tcs[LOLFT].u) / polyw;
@@ -173,20 +169,68 @@ void GLWall::SplitRightEdge(FFlatVertex *&ptr)
 //
 //==========================================================================
 
-void GLWall::CreateVertices(FFlatVertex *&ptr, bool nosplit)
+void GLWall::CreateVertices(FFlatVertex *&ptr, bool split)
 {
-	bool split = (gl_seamless && !nosplit && seg->sidedef != nullptr && !(seg->sidedef->Flags & WALLF_POLYOBJ) && !(flags & GLWF_NOSPLIT));
 	ptr->Set(glseg.x1, zbottom[0], glseg.y1, tcs[LOLFT].u, tcs[LOLFT].v);
 	ptr++;
 	if (split && glseg.fracleft == 0) SplitLeftEdge(ptr);
 	ptr->Set(glseg.x1, ztop[0], glseg.y1, tcs[UPLFT].u, tcs[UPLFT].v);
 	ptr++;
-	if (split && !(flags & GLWF_NOSPLITUPPER)) SplitUpperEdge(ptr);
+	if (split && !(flags & GLWF_NOSPLITUPPER && seg->sidedef->numsegs > 1)) SplitUpperEdge(ptr);
 	ptr->Set(glseg.x2, ztop[1], glseg.y2, tcs[UPRGT].u, tcs[UPRGT].v);
 	ptr++;
 	if (split && glseg.fracright == 1) SplitRightEdge(ptr);
 	ptr->Set(glseg.x2, zbottom[1], glseg.y2, tcs[LORGT].u, tcs[LORGT].v);
 	ptr++;
-	if (split && !(flags & GLWF_NOSPLITLOWER)) SplitLowerEdge(ptr);
+	if (split && !(flags & GLWF_NOSPLITLOWER) && seg->sidedef->numsegs > 1) SplitLowerEdge(ptr);
 }
 
+//==========================================================================
+//
+// 
+//
+//==========================================================================
+
+int GLWall::CountVertices()
+{
+	int cnt = 4;
+	vertex_t * vi = vertexes[0];
+	if (glseg.fracleft == 0 && vi != nullptr && vi->numheights)
+	{
+		int i = 0;
+
+		while (i<vi->numheights && vi->heightlist[i] <= zbottom[0]) i++;
+		while (i<vi->numheights && vi->heightlist[i] < ztop[0])
+		{
+			i++;
+			cnt++;
+		}
+	}
+	auto sidedef = seg->sidedef;
+	if (!(flags & (GLWF_NOSPLITLOWER | GLWF_NOSPLITUPPER)) && sidedef->numsegs > 1)
+	{
+		int cnt2 = 0;
+		for (int i = sidedef->numsegs - 2; i >= 0; i--)
+		{
+			float sidefrac = sidedef->segs[i]->sidefrac;
+			if (sidefrac >= glseg.fracright) continue;
+			if (sidefrac <= glseg.fracleft) break;
+			cnt2++;
+		}
+		if ((flags & (GLWF_NOSPLITLOWER | GLWF_NOSPLITUPPER)) == (GLWF_NOSPLITLOWER | GLWF_NOSPLITUPPER)) cnt2 <<= 1;
+		cnt += cnt2;
+	}
+	vi = vertexes[1];
+	if (glseg.fracright == 1 && vi != nullptr && vi->numheights)
+	{
+		int i = 0;
+
+		while (i<vi->numheights && vi->heightlist[i] <= zbottom[1]) i++;
+		while (i<vi->numheights && vi->heightlist[i] < ztop[1])
+		{
+			i++;
+			cnt++;
+		}
+	}
+	return cnt;
+}

src/gl/scene/gl_wall.h

@@ -266,6 +266,8 @@ private:
 	void SplitUpperEdge(FFlatVertex *&ptr);
 	void SplitLowerEdge(FFlatVertex *&ptr);
 
+	int CountVertices();
+
 public:
 
 	GLWall(GLSceneDrawer *drawer)

src/gl/scene/gl_walls.cpp

@@ -50,7 +50,7 @@ void FDrawInfo::AddWall(GLWall *wall)
 	if (translucent) // translucent walls
 	{
 		wall->ViewDistance = (r_viewpoint.Pos - (wall->seg->linedef->v1->fPos() + wall->seg->linedef->Delta() / 2)).XY().LengthSquared();
-		if (gl.buffermethod == BM_DEFERRED) wall->MakeVertices(true);
+		wall->MakeVertices(true);
 		auto newwall = drawlists[GLDL_TRANSLUCENT].NewWall();
 		*newwall = *wall;
 	}
@@ -73,7 +73,7 @@ void FDrawInfo::AddWall(GLWall *wall)
 		{
 			list = masked ? GLDL_MASKEDWALLS : GLDL_PLAINWALLS;
 		}
-		if (gl.buffermethod == BM_DEFERRED) wall->MakeVertices(false);
+		wall->MakeVertices(false);
 		auto newwall = drawlists[list].NewWall();
 		*newwall = *wall;
 	}
@@ -133,7 +133,7 @@ void GLWall::PutPortal(HWDrawInfo *di, int ptype)
 {
 	GLPortal * portal;
 
-	if (gl.buffermethod == BM_DEFERRED) MakeVertices(false);
+	MakeVertices(false);
 	switch (ptype)
 	{
 	// portals don't go into the draw list.

src/gl/scene/gl_walls_draw.cpp

@@ -154,9 +154,11 @@ void GLWall::MakeVertices(bool nosplit)
 {
 	if (vertcount == 0)
 	{
-		FFlatVertex *ptr = GLRenderer->mVBO->GetBuffer();
-		CreateVertices(ptr, nosplit);
-		vertcount = GLRenderer->mVBO->GetCount(ptr, &vertindex);
+		bool split = (gl_seamless && !nosplit && seg->sidedef != nullptr && !(seg->sidedef->Flags & WALLF_POLYOBJ) && !(flags & GLWF_NOSPLIT));
+		vertcount = split ? CountVertices() : 4;
+
+		FFlatVertex *ptr = GLRenderer->mVBO->Alloc(vertcount, &vertindex);
+		CreateVertices(ptr, split);
 	}
 }
 
@@ -170,25 +172,9 @@ void GLWall::MakeVertices(bool nosplit)
 
 void GLWall::RenderWall(int textured)
 {
+	assert(vertcount > 0);
 	gl_RenderState.Apply();
 	gl_RenderState.ApplyLightIndex(dynlightindex);
-	if (gl.buffermethod != BM_DEFERRED)
-	{
-		MakeVertices(!!(textured&RWF_NOSPLIT));
-	}
-	else if (vertcount == 0)
-	{
-		// This should never happen but in case it actually does, use the quad drawer as fallback (without edge splitting.)
-		// This way it at least gets drawn.
-		FQuadDrawer qd;
-		qd.Set(0, glseg.x1, zbottom[0], glseg.y1, tcs[LOLFT].u, tcs[LOLFT].v);
-		qd.Set(1, glseg.x1, ztop[0], glseg.y1, tcs[UPLFT].u, tcs[UPLFT].v);
-		qd.Set(2, glseg.x2, ztop[1], glseg.y2, tcs[UPRGT].u, tcs[UPRGT].v);
-		qd.Set(3, glseg.x2, zbottom[1], glseg.y2, tcs[LORGT].u, tcs[LORGT].v);
-		qd.Render(GL_TRIANGLE_FAN);
-		vertexcount += 4;
-		return;
-	}
 	GLRenderer->mVBO->RenderArray(GL_TRIANGLE_FAN, vertindex, vertcount);
 	vertexcount += vertcount;
 }