Question

In my next project, I’m trying to learn JOGL. The result should be a simple 2d animation.

I’ve heard, that a texture must be 2^n*2^n in size. Can I still use images which don’t have this size, or do I have to edit all images in advance? What do I have to take care of, when using such textures?

As an example, I want to show a kind of progress bar, whose image is at the size of 1024*96px. Do I have to define a quad (eg.1024*1024 in size if you calculate the pixels) and use alpha blending to show only the “filled” part? Or are texture coordinates the way to go?

[Edit]
Works, solution looks like this (using orthogonal projection):

@Override
public void init(GLAutoDrawable drawable) {
    GL gl = drawable.getGL(); // get GL
    glu = new GLU();
    //...
    t  = load(".\\TEXTURES\\ProgressBarBG.png");
            //...
}

   public Texture load(String fileName){
    Texture text = null;
    try{
        text = TextureIO.newTexture(new File(fileName), false);
        text.setTexParameteri(GL.GL_TEXTURE_MAG_FILTER, GL.GL_NEAREST);
        text.setTexParameteri(GL.GL_TEXTURE_MIN_FILTER, GL.GL_NEAREST);
    }catch(Exception e){
        System.out.println(e.getMessage());
        System.out.println("Error loading texture " + fileName);
    }
    return text;
}

    private void drawProgressBG(GL gl, int z) {

    gl.glPushMatrix();
    gl.glLoadIdentity();

    gl.glEnable(GL.GL_BLEND);
    gl.glBlendFunc(GL.GL_SRC_ALPHA, GL.GL_ONE_MINUS_SRC_ALPHA);

    gl.glEnable(GL.GL_ALPHA_TEST);
    gl.glAlphaFunc(GL.GL_GREATER, 0); // only render if alpha > 0

    // don't show source alpha parts in the destination
    gl.glEnable(GL.GL_TEXTURE_2D);

    TextureCoords tc = t.getImageTexCoords();

    t.enable();
    t.bind();


    gl.glTexEnvi(GL.GL_TEXTURE_ENV, GL.GL_TEXTURE_ENV_MODE,
            GL.GL_REPLACE);

    gl.glBegin(GL.GL_QUADS);

    gl.glTexCoord2f(tc.left(), tc.bottom()); gl.glVertex3f( 0f, 0f, z);
    gl.glTexCoord2f(tc.right(), tc.bottom()); gl.glVertex3f( 1024f, 0f, z);
    gl.glTexCoord2f(tc.right(), tc.top()); gl.glVertex3f( 1024f, 96f, z);
    gl.glTexCoord2f(tc.left(), tc.top()); gl.glVertex3f( 0f, 96f, z);

    gl.glEnd();

    gl.glDisable(GL.GL_TEXTURE_2D);
    // switch back to modulation of quad colours and texture
    gl.glTexEnvi(GL.GL_TEXTURE_ENV, GL.GL_TEXTURE_ENV_MODE,
    GL.GL_MODULATE);
    gl.glDisable(GL.GL_ALPHA); // switch off transparency
    gl.glDisable(GL.GL_BLEND);


    gl.glPopMatrix();

}

[/EDIT]

Answer 1

I don’t think it has to be 2^n anymore. You could test it easily
nehe.gamedev.net has great opengl tutorials and some also in JOGL. Using only 9% of your 1024*1024 texture is a big waste of video ram. You’d better edit it. Use texture coordinates if you only need a portion of your texture, that’s why we have them.