How can I make OpenGL textures scale without becoming blurry?

Question

I'm using OpenGL through LWJGL.

I have a 16x16 textured quad rendering at 16x16. When I change it's scale amount, the quad grows, then becomes blurrier as it gets larger.

How can I make it scale without becoming blurry, like in Minecraft.

Here is the code inside my RenderableEntity object:

public void render(){       
    Color.white.bind();
    this.spriteSheet.bind();        
    GL11.glBegin(GL11.GL_QUADS);
        GL11.glTexCoord2f(0,0);
        GL11.glVertex2f(this.x, this.y);
        GL11.glTexCoord2f(1,0);
        GL11.glVertex2f(getDrawingWidth(), this.y);
        GL11.glTexCoord2f(1,1);
        GL11.glVertex2f(getDrawingWidth(), getDrawingHeight());
        GL11.glTexCoord2f(0,1);
        GL11.glVertex2f(this.x, getDrawingHeight());
     GL11.glEnd();

}

And here is code from my initGL method in my game class

GL11.glEnable(GL11.GL_TEXTURE_2D);
GL11.glClearColor(0.46f,0.46f,0.90f,1.0f);
GL11.glViewport(0,0,width,height);
GL11.glOrtho(0,width,height,0,1,-1);

And here is the code that does the actual drawing

public void start(){
    initGL(800,600);
    init();

    while(true){
        GL11.glClear(GL11.GL_COLOR_BUFFER_BIT);

        for(int i=0;i<entities.size();i++){
            ((RenderableEntity)entities.get(i)).render();
        }

        Display.update();
        Display.sync(100);

        if(Display.isCloseRequested()){
            Display.destroy();
            System.exit(0);
        }
    }
}

Answer 1

You need to change the texture magnification type, like so:

 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);

Read about glTexParameter.

Answer 2

You can't. The nature of any kind of digital data is that once information has been removed it can never be put back, and likewise you can't fill in information that was never there in the first place - the best you can do is a rough approximation, which gives you blurriness.

Using GL_NEAREST won't blur but it will become pixellated instead.

The solution is to use a larger texture with mipmaps. That way you get good quality no matter what size the geometry being textured is.

Answer 3

I've experienced this issue first hand - making a block-based game with low res (8px * 8px) textures. No matter how far close or how far the camera was, the textures were being cross "blended" by OpenGL's default settings - they appeared blurry.

You need to enable "nearest" magnification to disable bilinear filtering. That is, when the camera is zoomed in close to the texture; each pixel is defined as the colour of the texel that is closest - no blending.

You do this with these two lines:

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);