- predefine the vertex data for the blend overlay which will never change throughout the lifetime of the GLRenderer object.

src/gl/data/gl_vertexbuffer.cpp

@@ -109,7 +109,7 @@ void FSimpleVertexBuffer::set(FSimpleVertex *verts, int count)
 //
 //==========================================================================
 
-FFlatVertexBuffer::FFlatVertexBuffer()
+FFlatVertexBuffer::FFlatVertexBuffer(int width, int height)
 : FVertexBuffer(gl.buffermethod == BM_PERSISTENT)
 {
 	if (gl.buffermethod == BM_PERSISTENT)
@@ -125,7 +125,22 @@ FFlatVertexBuffer::FFlatVertexBuffer()
 		vbo_shadowdata.Reserve(BUFFER_SIZE);
 		map = new FFlatVertex[BUFFER_SIZE];
 	}
-	mNumReserved = mIndex = mCurIndex = 0;
+	mIndex = mCurIndex = 0;
+	mNumReserved = 8;
+	vbo_shadowdata.Resize(mNumReserved);
+
+	// the first quad is reserved for handling coordinates through uniforms.
+	vbo_shadowdata[0].Set(1, 0, 0, 0, 0);
+	vbo_shadowdata[1].Set(2, 0, 0, 0, 0);
+	vbo_shadowdata[2].Set(3, 0, 0, 0, 0);
+	vbo_shadowdata[3].Set(4, 0, 0, 0, 0);
+
+	// and the second one for the fullscreen quad used for blend overlays.
+	vbo_shadowdata[4].Set(0, 0, 0, 0, 0);
+	vbo_shadowdata[5].Set(0, (float)height, 0, 0, 0);
+	vbo_shadowdata[6].Set((float)width, 0, 0, 0, 0);
+	vbo_shadowdata[7].Set((float)width, (float)height, 0, 0, 0);
+
 }
 
 FFlatVertexBuffer::~FFlatVertexBuffer()
@@ -350,7 +365,6 @@ void FFlatVertexBuffer::UpdatePlaneVertices(sector_t *sec, int plane)
 
 void FFlatVertexBuffer::CreateVBO()
 {
-	vbo_shadowdata.Resize(mNumReserved);
 	CreateFlatVBO();
 	mCurIndex = mIndex = vbo_shadowdata.Size();
 	memcpy(map, &vbo_shadowdata[0], vbo_shadowdata.Size() * sizeof(FFlatVertex));

src/gl/data/gl_vertexbuffer.h

@@ -84,7 +84,7 @@ class FFlatVertexBuffer : public FVertexBuffer
 public:
 	TArray<FFlatVertex> vbo_shadowdata;	// this is kept around for updating the actual (non-readable) buffer and as stand-in for pre GL 4.x
 
-	FFlatVertexBuffer();
+	FFlatVertexBuffer(int width, int height);
 	~FFlatVertexBuffer();
 
 	void BindVBO();

src/gl/renderer/gl_renderer.cpp

@@ -113,7 +113,7 @@ FGLRenderer::FGLRenderer(OpenGLFrameBuffer *fb)
 void gl_LoadModels();
 void gl_FlushModels();
 
-void FGLRenderer::Initialize()
+void FGLRenderer::Initialize(int width, int height)
 {
 	mBuffers = new FGLRenderBuffers();
 	mBloomExtractShader = new FBloomExtractShader();
@@ -137,7 +137,7 @@ void FGLRenderer::Initialize()
 	glpart = FTexture::CreateTexture(Wads.GetNumForFullName("glstuff/glpart.png"), FTexture::TEX_MiscPatch);
 	mirrortexture = FTexture::CreateTexture(Wads.GetNumForFullName("glstuff/mirror.png"), FTexture::TEX_MiscPatch);
 
-	mVBO = new FFlatVertexBuffer;
+	mVBO = new FFlatVertexBuffer(width, height);
 	mSkyVBO = new FSkyVertexBuffer;
 	if (gl.lightmethod != LM_SOFTWARE) mLights = new FLightBuffer();
 	else mLights = NULL;

src/gl/renderer/gl_renderer.h

@@ -129,7 +129,7 @@ public:
 	void SetViewAngle(DAngle viewangle);
 	void SetupView(float viewx, float viewy, float viewz, DAngle viewangle, bool mirror, bool planemirror);
 
-	void Initialize();
+	void Initialize(int width, int height);
 
 	void CreateScene();
 	void RenderMultipassStuff();

src/gl/scene/gl_scene.cpp

@@ -525,16 +525,8 @@ void gl_FillScreen()
 	gl_RenderState.AlphaFunc(GL_GEQUAL, 0.f);
 	gl_RenderState.EnableTexture(false);
 	gl_RenderState.Apply();
-	FFlatVertex *ptr = GLRenderer->mVBO->GetBuffer();
-	ptr->Set(0, 0, 0, 0, 0);
-	ptr++;
-	ptr->Set(0, (float)SCREENHEIGHT, 0, 0, 0);
-	ptr++;
-	ptr->Set((float)SCREENWIDTH, 0, 0, 0, 0);
-	ptr++;
-	ptr->Set((float)SCREENWIDTH, (float)SCREENHEIGHT, 0, 0, 0);
-	ptr++;
-	GLRenderer->mVBO->RenderCurrent(ptr, GL_TRIANGLE_STRIP);
+	// The fullscreen quad is stored at index 4 in the main vertex buffer.
+	glDrawArrays(GL_TRIANGLE_STRIP, 4, 4);
 }
 
 //==========================================================================

src/gl/system/gl_framebuffer.cpp

@@ -164,7 +164,7 @@ void OpenGLFrameBuffer::InitializeState()
 	//int h = GetHeight();
 	//glViewport(0, (trueH - h)/2, GetWidth(), GetHeight()); 
 
-	GLRenderer->Initialize();
+	GLRenderer->Initialize(GetWidth(), GetHeight());
 	GLRenderer->SetOutputViewport(nullptr);
 	Begin2D(false);
 }