[SOLVED] Gap Between Edge of Window and Viewport [LWJGL]

Newbie & Debugging Questions
#1

So this is my problem.

I’m not sure why I’m getting the black gap and it’s really bugging me. It disappears when I resize the window. This is my code:

Setting up the window:

Display.setDisplayMode(new DisplayMode(800, 600));

Initializing the camera:

glOrtho(0, 800, 0, 600, 1, -1);

Rendering:

@Override
public void render() {
	glClearColor(1f, 0f, 0f, 0f);
	glClear(GL_COLOR_BUFFER_BIT);

	glPushMatrix();
	glTranslatef(x, y, 0);

	glBegin(GL_QUADS);
	glVertex2f(0, 0);
	glVertex2f(100, 0);
	glVertex2f(100, 100);
	glVertex2f(0, 100);
	glEnd();
	glPopMatrix();
}

Am I missing something or am I doing something wrong?

#2

Did you set the viewport? Can I see where you initialize your matrices?

#3

Only correcting when you resize? Try looking in your resize method and see if there’s anything there that’s not there when you create the window.

#4

Oh my resize method is simply

@Override
public void resize() {
	glViewport(0, 0, Display.getWidth(), Display.getHeight());
}

I tried calling resize after I set up the camera but nothing happens.

Do you mean this?

@Override
public void initialize() {
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();

	glMatrixMode(GL_MODELVIEW);
	glOrtho(0, 800, 0, 600, 1, -1);
}

Should I be replacing the projection matrix with the identity matrix?

#5

And you call resize straight away after initializing the game? Throw in a resize call after your modelview matrix call.

#6

I’ve already tried that and it doesn’t work. I’m really confused. :confused:
This is my game loop:


@Override
public void gameLoop() {
	long currentFrame;
	long lastFrame = getCurrentTime();
	initialize();

	while (!Display.isCloseRequested()) {
		currentFrame = getCurrentTime();
		update(currentFrame - lastFrame);

		if (Display.wasResized()) {
			resize();
		}

		if (Display.isVisible() || Display.isDirty()) {
			render();
			if (Display.isActive()) {
				Display.sync(60);
			} else {
				try {
					Thread.sleep(100);
				} catch (InterruptedException e) {
					System.out.println(NAME + ": Error sleeping.");
				}
			}
		}

		Display.update();
		lastFrame = currentFrame;
	}

	dispose();
}
#7

Huh, that’s odd! I’ve had it happen to me before, but I just ignored it and eventually I must have changed some code around and it went away… Hold on I’ll go look for some code for you to try.

Edit:
In your render method you clear the color before clearing the screen, switch those two, I don’t think it will make much of a difference, but I think they should be switched anyway.

This code is straight from my NEngine library, and I know it works. Here’s how I create a new window:


public static void createWindow(int width, int height, String title, boolean mouseCaptured) {
		try {
			Display.setDisplayMode(new DisplayMode(width, height));
			Display.setTitle(title);
			Mouse.setGrabbed(mouseCaptured);
			Display.create();
		} catch (LWJGLException e) {
			e.printStackTrace();
		}
	}

Here’s how I set up my viewport and ortho projection:


public static void renderOrtho(double left, double right, double bottom, double top){
		glMatrixMode(GL_PROJECTION);
		glLoadIdentity();
		
		glMatrixMode(GL_MODELVIEW);
		glOrtho(left, right, bottom, top, 1, -1);
		glViewport(0, 0, Display.getWidth(), Display.getHeight());
	}

Generally, I call that method with these parameters:


ScreenTools.renderOrtho(0, WIDTH, 0, HEIGHT);

Obviously, this would put the origin in the bottom left corner.

#8

Aren’t I clearing the screen by clearing the colour? :-\

#9

Well, glClear(GL_COLOR_BUFFER_BIT) is clearing the color buffer, which with the glClearColor call you just added color I believe? I don’t know, I haven’t looked too much into it, but I’ve never seen any code where someone clears the color and then the buffer.

Edit:
Try making a new project and just create a window and update it, no game loop or anything. Then clear the color and add in the matrix calls and see if the problem still persists.

#10

Oh I fixed it by changing this:


public Application() throws LWJGLException {
	Display.setDisplayMode(new DisplayMode(800, 600));
	Display.setVSyncEnabled(true);
	Display.setTitle("A game using the LWJGL");
	Display.create();
	Display.setResizable(true);
}

to this:


public Application() throws LWJGLException {
	Display.setDisplayMode(new DisplayMode(800, 600));
	Display.setVSyncEnabled(true);
	Display.setTitle("A game using the LWJGL");
	Display.setResizable(true);
	Display.create();
}

I was thinking the problem was with the viewport. >:(

I thought the glClearColor(…) call set the colour of the color buffer and glClear(GL_COLOR_BUFFER_BIT) actually cleared the colour buffer. Please correct me if I’m wrong.

#11

Ah yes, that resizable call would do it, good job! Also, vSync is only useful in a full screen context, and it would just hog your resources in a non full screen window, so I wouldn’t recommend enabling it!

About the glClear and stuff, this is straight from the docs:

glClearColor - glClearColor specifies the red, green, blue, and alpha values used by glClear to clear the color buffers. Values specified by glClearColor are clamped to the range 0 1 .

glClear - glClear sets the bitplane area of the window to values previously selected by glClearColor, glClearDepth, and glClearStencil.

Huh, I guess I was wrong! Apparently you’re right, glClear clears the buffer to the color specified by glClearColor. Well, thanks for telling me that :slight_smile: