Why do I have an uneven sprite line, when zooming and moving in libGDX?

Question

I'm having trouble zooming in and moving my sprites. I made a simple drawing to demonstrate what happens.

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No zoom:

Zoomed out:

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Some lines disappear, when moving a sprite. If I use a filter, this effect improves, but the image is now blurred.

    textureParameter = new TextureLoader.TextureParameter();

    textureParameter.genMipMaps = true;
    textureParameter.minFilter = Texture.TextureFilter.MipMapLinearLinear;
    textureParameter.magFilter = Texture.TextureFilter.Linear;
    game.getManager().load(ResourcesString.image, Texture.class, textureParameter);

This is the way I deal with my camera:

//Code
private void zoomCamera(Vector3 origin, float scale){
    main.orthographicCamera.update();
    Vector3 oldUnprojection = main.orthographicCamera.unproject(origin.cpy()).cpy();
    if(scale > zoomMin) scale = zoomMin;
    if(scale < zoomMax) scale = zoomMax;
    main.orthographicCamera.zoom = scale;
    main.orthographicCamera.update();
    Vector3 newUnprojection = main.orthographicCamera.unproject(origin.cpy()).cpy();
    main.orthographicCamera.position.add(oldUnprojection.cpy().add(newUnprojection.cpy().scl(-1f)));
    main.orthographicCamera.update();
}

public void pan(float x, float y, float deltaX, float deltaY) {
    main.orthographicCamera.translate(deltaX * -2f, deltaY * 2f);
}

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Why do my lines display as uneven when I zoom out, and how do I fix it?

Answer 1

If you have a sprite that has a line that is one pixel wide and you're displaying that in a viewport that is the same as the resolution of the display/window the all is fine, but you'll get the artifacts you're describing if you (for example) zoom out so that the viewport is four times larger than the display. At that point the pixels in the sprite needs to be rendered at half their size which is impossible due to hardware limitations, instead the pixel on screen is rendered as the blend between two pixels, which is why it looks like a half line.

Setting the filtering to Nearest will combat this to a certain extent but comes with the drawback of things looking "pixely".

If what you really need us for the lines in the sprite to always be exactly 1 pixel in width, regardles of resolution, then look into using the ShapeRenderer instead.