Question

I am using slick for java since a few days and got a serious problem.
If i run a completely empty apllication (it just shows the fps) with a solution of 800×600 i get a fps count between 700 and 800.
If I now draw an array with 13300 entries as a grid of green and white rectangles, the fps drop to something around 70.

With more entries in the array it becomes really slow.
For example in a solution of 1024×768 and an array with 21760 entries the fps drop to 40.

How i draw a single entry:

public void draw(Graphics graphics){
    graphics.setColor(new Color(getColor().getRed(), getColor().getGreen(), getColor().getBlue(), getColor().getAlpha()));

    graphics.fillRect(getPosition().x, getPosition().y, getSize().x, getSize().y);

    Color_ARGB white = new Color_ARGB(Color_ARGB.ColorNames.WHITE);
    graphics.setColor(new Color(white.getRed(), white.getGreen(), white.getBlue(), white.getAlpha()));
}

And this is how I draw the complete array:

public void draw(Graphics graphics) {
    for (int ix = 0; ix < getWidth(); ix++) {
        for (int iy = 0; iy < getHeight(); iy++) {
            getGameGridAt(ix, iy).draw(graphics);
        }
    }
}

In my opinion 21760 is not that much.
Is there anything wrong with my code or is slick just too slow to draw so much rectangles?

Answer 1

You only want to draw rectangles that are on the screen. If your screen bounds go from 0 to 1024 in the x direction and from 0 to 768 in the y direction, then you only want to loop through rectangles that are inside those bounds and then only draw those rectangles. I can’t imagine you are trying to draw 21760 rectangles inside those bounds.

If you are, then try creating one static rectangle and then just try drawing that ONE in all of the different positions you need to draw it at rather than creating a new one every time. For example, in a game I am making, I might have 1000 tiles that are “grass” tiles, but all 1000 of those share the same static texture. So I only need to reference one image rather than each tile creating its own.

Each rectangle can still have a unique state. Just make your own rectangle class and have a static final Image that holds a 5*5 image. Each rectangle will use this image when it needs to be drawn. You can still have unique properties for each rectangle. For example, private Vector2f position, private boolean isAlive, etc