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thekilla1234

OpenGL SDL/OpenGL - Slow Rendering With Textures Close Up

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I have had this problem for a while now and I've searched everywhere for an answer to no avail. Maybe I'm terrible at using Google, enlighten me if you please. Anyway, on with the problem. Basically, I have a really low polygon house, which is rendered as triangles using glDrawElements(). It is actually drawn with two glDrawElements() calls, since the model is split into two different parts to draw the brick and slate textures on the seperate parts of the house. The textures used are 256 x 256 in size, as shown below: http://img716.imageshack.us/img716/1228/brick.png http://img97.imageshack.us/img97/570/slate.png Quick PC spec: Windows 7 2.4GHz Intel Q6600 Quad Core NVidia GeForce 9600GT 512MB GDDR3 3GB Memory Compiler: Visual C++ 2008 Express The application renders really smoothly when the house is at a distance, such as in the screenshot below: http://img30.imageshack.us/img30/6469/housesmall.png However, once the house gets closer, and the triangles take up more of the screen, the application runs slower and slower until the triangles fill the window, in which it starts running at about 10fps. The screenshot below ran at about 12.5fps: http://img41.imageshack.us/img41/4859/houselarge.png When textures are enabled, this problem really slows the application down. There is a very small slow down in the close up situation with no textures, but it is a lot smaller. Also, I should note that if part of the window is placed part way off the screen while the house is really close, the application speeds up to almost full speed. Therefore, there is something wrong with SDL_GL_SwapBuffers() when OpenGL is required to render pixels that take up most of the window. Below is a quick profile result (Time units are milliseconds): http://img203.imageshack.us/img203/1290/profilem.png Disregard the large 'new'/'delete' count, they are done during calling reserve() on a vector in setupLighting(), which is a function that makes no difference to the problem (I have tried removing it during certain tests). The highlighted row is the SDL_GL_SwapBuffers() command, which is executing at an average of 81 milliseconds, or 12.5fps. Of course, I wouldn't believe SDL_GL_SwapBuffers() is the problem, it will be somewhere in my own code, but I can't think for my life what it is. Maybe blazingly obvious, who knows, heres some code anyway, see what you can find. All classes I have created have the 'cge' prefix, just for the record. Here is my window creation member function, which simply sets up the SDL window ready for OpenGL rendering
void cgeRenderWindow::initialize()
{
	if(SDL_Init(SDL_INIT_EVERYTHING) != CGE_SDL_INIT_SUCCESSFUL)
		exit(0);

	GLuint renderFlags;
	
	if(mWindowMode == CGE_WINDOWED)
		renderFlags = SDL_OPENGL;
	else
		renderFlags = SDL_OPENGL | SDL_FULLSCREEN;
	
	SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, CGE_DOUBLE_BUFFERING_ENABLE);

	mRenderSurface = SDL_SetVideoMode(mWindowWidth, mWindowHeight, mWindowMode, renderFlags);
}




cgeScene::initialize() sets up OpenGL as follows.
void cgeScene::initialize() const
{
	glEnable(GL_CULL_FACE);
	glEnable(GL_DEPTH_TEST);
	glEnable(GL_TEXTURE_2D);
	glEnable(GL_LIGHTING);
	glEnable(GL_COLOR_MATERIAL);

	glFrontFace(GL_CW);
	glShadeModel(GL_SMOOTH);
	glColorMaterial(GL_FRONT, GL_AMBIENT_AND_DIFFUSE);

	glEnableClientState(GL_VERTEX_ARRAY);
	glEnableClientState(GL_NORMAL_ARRAY);
	glEnableClientState(GL_TEXTURE_COORD_ARRAY);

	glClearColor(mClearColor.mRed, mClearColor.mGreen, mClearColor.mBlue, mClearColor.mAlpha);
	disableAllLights();
	mCamera.initialize();
}




Commenting out glEnable(GL_TEXTURE_2D) here vastly improves the speed of the close up geometry, though it still runs slower than at a distance. mCamera.initialize() calls cgeCamera::initialize(), which sets up the viewport. It uses a rectangle class I made which returns floats, that explains the casts made, though that matters not.
void cgeCamera::initialize() const
{
	// Rectangle coordinates are floats, glViewport takes ints (GLsizei = int), convert appropriately
	glViewport(static_cast<GLint>(mViewportBoundary.mBottomLeftCorner.mX), static_cast<GLint>(mViewportBoundary.mBottomLeftCorner.mY), static_cast<GLint>(mViewportBoundary.getWidth()), static_cast<GLint>(mViewportBoundary.getHeight()));

	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();

	// Division by 0 avoidance
	GLfloat aspectRatio(mViewportBoundary.getWidth() / (mViewportBoundary.getHeight() == 0 ? 1 : mViewportBoundary.getHeight()));

	// Creates a projection matrix using the corresponding parameter values
	gluPerspective(mFieldOfView, aspectRatio, mNearPlane, mFarPlane);

	glMatrixMode(GL_MODELVIEW);
}




The main rendering function. Called once per loop of the infinite loop in main.
void cgeScene::render()
{
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();

	cgeMatrix cameraTranslationMatrix;
	cameraTranslationMatrix.setTranslation(-mCamera.mPosition);
	glMultMatrixf((cameraTranslationMatrix * mCamera.mRotationMatrix).mMatrix); 

	for(GLuint modelInstance = 0; modelInstance < mModelInstances.size(); modelInstance++)
	{
		glPushMatrix();
			//setupLighting(mModelInstances[modelInstance].mPosition);
			mModelInstances[modelInstance].draw();
		glPopMatrix();
	}

	SDL_GL_SwapBuffers();
}




setupLighting() makes a very small difference to the speed, but I commented it out just to make sure. All matrix multiplications make very little difference, I have tried commenting those out also in previous tests. That leaves cgeModelInstances::draw(). Only one model instance is drawn, which is the house shown. The model parts contain triangle information used in the glPointer() functions, each model part corresponding to a certain material (in this case, this is 2 model parts for the 2 textures). Here is cgeModelInstances::draw().
void cgeModelInstance::draw()
{
	cgeMatrix modelTranslationMatrix;
	modelTranslationMatrix.setTranslation(mPosition);
	glMultMatrixf((modelTranslationMatrix * mRotationMatrix).mMatrix);

	// Draw each model part
	for(GLuint i = 0; i < mModel->getModelParts().size(); i++)
	{
		glVertexPointer(CGE_VERTEX_DIMENSIONS, GL_FLOAT, 0, &(mModel->getModelParts()[i].getVertecies()[0]));
		glNormalPointer(GL_FLOAT, 0, &(mModel->getModelParts()[i].getNormals()[0]));
		glTexCoordPointer(CGE_TEXTURE_DIMENSIONS, GL_FLOAT, 0, &(mModel->getModelParts()[i].getTextureCoordinates()[0]));
		
		//glColor4f(mColor.mRed, mColor.mGreen, mColor.mBlue, mColor.mAlpha);

		// If there is no texture, unbind
		if(!mModel->getModelParts()[i].mTexture)
			glBindTexture(GL_TEXTURE_2D, CGE_NO_TEXTURE);
		else
			glBindTexture(GL_TEXTURE_2D, mModel->getModelParts()[i].mTexture->getIdentifier());
		
		glDrawElements(GL_TRIANGLES, mModel->getModelParts()[i].getIndecies().size(), GL_UNSIGNED_INT, &(mModel->getModelParts()[i].getIndecies()[0]));
	}
}




Again, the matrix multiplication makes very little difference to the speed. My textures are created as follows.
	// Generate a new texture object and bind to it
	glGenTextures(1, &mIdentifier);
	glBindTexture(GL_TEXTURE_2D, mIdentifier);

	// Create the texture from the pixel data (located at the address of pixelData[0])
	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 256, 256, 0, GL_BGRA, GL_UNSIGNED_BYTE, &pixelData[0]);

	// Set the parameters for this new texture
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);




Note that I have used the 256 constant here to make sure they are 256 x 256 textures, though they are anyway, so this shouldn't make any difference. I was wondering if anyone else has had this close up texture problem before, whether it's a common problem or if it's my code. If you need more information, feel free to ask. [Edited by - thekilla1234 on March 16, 2010 9:31:49 AM]

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The long lines are making your post really wide (on my monitor, at least). Could you possibly edit your post and use [ source ] tags rather than [ code ] tags? (You can also use HTML to make your images clickable, which will probably make people more likely to check them out.)

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Quote:
The highlighted row is the SDL_GL_SwapBuffers() command, which is executing at an average of 81 milliseconds, or 12.5fps. Of course, I wouldn't believe SDL_GL_SwapBuffers() is the problem, it will be somewhere in my own code, but I can't think for my life what it is.

Calling swapBuffers makes the driver flush the command queue. Basically the command blocks until the GPU actually completed all rendering and has swapped the buffers, that's why it is showing up in the profiler.

This might sound silly, but can you use glGetString with GL_VENDOR to determine if you are for whatever reason using the old Microsoft software OpenGL implementation?

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It does seem to be running from Microsoft's implementation indeed. I didn't think this would be a problem for such a small mesh. Are extensions the solution to this, or is it something along the lines of the .dll I have? I was planning extensions later once I had the basics down, so if that is the problem, I shall add them now.

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Quote:
Original post by thekilla1234
It does seem to be running from Microsoft's implementation indeed. I didn't think this would be a problem for such a small mesh. Are extensions the solution to this, or is it something along the lines of the .dll I have? I was planning extensions later once I had the basics down, so if that is the problem, I shall add them now.


No, the solution is to use a hardware OpenGL implementation. You have problems creating your GL context, and it's fallbacking to a software implementation.

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Hah, figured out the problem, and an embarassing one at that. I had a copy of Microsoft's opengl32.dll in my executable's local directory. Deleted it and the FPS shot way up.

Thanks for pointing me in the right direction.

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