- use static buffer data and a uniform to handle the texture positioning of the present shader.

That's again one less write access to the buffer. The uniform method was chosen because this way a buffer update can be completely avoided, and setting a single uniform is a lot cheaper and simpler to handle.

src/gl/data/gl_vertexbuffer.cpp

@@ -126,7 +126,7 @@ FFlatVertexBuffer::FFlatVertexBuffer(int width, int height)
 		map = new FFlatVertex[BUFFER_SIZE];
 	}
 	mIndex = mCurIndex = 0;
-	mNumReserved = 8;
+	mNumReserved = 12;
 	vbo_shadowdata.Resize(mNumReserved);
 
 	// the first quad is reserved for handling coordinates through uniforms.
@@ -141,6 +141,12 @@ FFlatVertexBuffer::FFlatVertexBuffer(int width, int height)
 	vbo_shadowdata[6].Set((float)width, 0, 0, 0, 0);
 	vbo_shadowdata[7].Set((float)width, (float)height, 0, 0, 0);
 
+	// and this is for the postprocessing copy operation
+	vbo_shadowdata[8].Set(-1.0f, -1.0f, 0, 0.0f, 0.0f);
+	vbo_shadowdata[9].Set(-1.0f, 1.0f, 0, 0.0f, 1.f);
+	vbo_shadowdata[10].Set(1.0f, -1.0f, 0, 1.f, 0.0f);
+	vbo_shadowdata[11].Set(1.0f, 1.0f, 0, 1.f, 1.f);
+
 }
 
 FFlatVertexBuffer::~FFlatVertexBuffer()

src/gl/renderer/gl_postprocess.cpp

@@ -108,16 +108,11 @@ EXTERN_CVAR(Float, vid_brightness)
 EXTERN_CVAR(Float, vid_contrast)
 
 
-void FGLRenderer::RenderScreenQuad(float maxU, float maxV)
+void FGLRenderer::RenderScreenQuad()
 {
-	FFlatVertex *ptr = mVBO->GetBuffer();
 	mVBO->BindVBO();
 	gl_RenderState.ResetVertexBuffer();
-	ptr->Set(-1.0f, -1.0f, 0, 0.0f, 0.0f); ptr++;
-	ptr->Set(-1.0f, 1.0f, 0, 0.0f, maxV); ptr++;
-	ptr->Set(1.0f, -1.0f, 0, maxU, 0.0f); ptr++;
-	ptr->Set(1.0f, 1.0f, 0, maxU, maxV); ptr++;
-	mVBO->RenderCurrent(ptr, GL_TRIANGLE_STRIP);
+	glDrawArrays(GL_TRIANGLE_STRIP, 8, 4);
 }
 
 //-----------------------------------------------------------------------------
@@ -357,9 +352,10 @@ void FGLRenderer::CopyToBackbuffer(const GL_IRECT *bounds, bool applyGamma)
 			mPresentShader->Contrast.Set(clamp<float>(vid_contrast, 0.1f, 3.f));
 			mPresentShader->Brightness.Set(clamp<float>(vid_brightness, -0.8f, 0.8f));
 		}
+		mPresentShader->Scale.Set(mScreenViewport.width / (float)mBuffers->GetWidth(), mScreenViewport.height / (float)mBuffers->GetHeight());
 		mBuffers->BindCurrentTexture(0);
 		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
 		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
-		RenderScreenQuad(mScreenViewport.width / (float)mBuffers->GetWidth(), mScreenViewport.height / (float)mBuffers->GetHeight());
+		RenderScreenQuad();
 	}
 }

src/gl/renderer/gl_renderer.h

@@ -153,7 +153,7 @@ public:
 	unsigned char *GetTextureBuffer(FTexture *tex, int &w, int &h);
 	void SetupLevel();
 
-	void RenderScreenQuad(float maxU = 1.0f, float maxV = 1.0f);
+	void RenderScreenQuad();
 	void SetFixedColormap (player_t *player);
 	void WriteSavePic (player_t *player, FILE *file, int width, int height);
 	void EndDrawScene(sector_t * viewsector);

src/gl/shaders/gl_presentshader.cpp

@@ -53,7 +53,7 @@ void FPresentShader::Bind()
 {
 	if (!mShader)
 	{
-		mShader.Compile(FShaderProgram::Vertex, "shaders/glsl/screenquad.vp", "", 330);
+		mShader.Compile(FShaderProgram::Vertex, "shaders/glsl/screenquadscale.vp", "", 330);
 		mShader.Compile(FShaderProgram::Fragment, "shaders/glsl/present.fp", "", 330);
 		mShader.SetFragDataLocation(0, "FragColor");
 		mShader.Link("shaders/glsl/present");
@@ -63,6 +63,7 @@ void FPresentShader::Bind()
 		Gamma.Init(mShader, "Gamma");
 		Contrast.Init(mShader, "Contrast");
 		Brightness.Init(mShader, "Brightness");
+		Scale.Init(mShader, "UVScale");
 	}
 	mShader.Bind();
 }

src/gl/shaders/gl_presentshader.h

@@ -12,6 +12,7 @@ public:
 	FBufferedUniform1f Gamma;
 	FBufferedUniform1f Contrast;
 	FBufferedUniform1f Brightness;
+	FBufferedUniform2f Scale;
 
 private:
 	FShaderProgram mShader;

src/gl/shaders/gl_shader.h

@@ -123,6 +123,17 @@ public:
 			glUniform2fv(mIndex, 1, newvalue);
 		}
 	}
+
+	void Set(float f1, float f2)
+	{
+		if (mBuffer[0] != f1 || mBuffer[1] != f2)
+		{
+			mBuffer[0] = f1;
+			mBuffer[1] = f2;
+			glUniform2fv(mIndex, 1, mBuffer);
+		}
+	}
+
 };
 
 class FBufferedUniform4f

wadsrc/static/shaders/glsl/screenquadscale.vp

@@ -0,0 +1,11 @@
+
+in vec4 PositionInProjection;
+in vec2 UV;
+uniform vec2 UVScale;
+out vec2 TexCoord;
+
+void main()
+{
+	gl_Position = PositionInProjection;
+	TexCoord = UV * UVScale;
+}