I added an image as plane B z=0. Then I added another image as plane X z=0. X is above B as I wanted, X uses B as background image. But when I walk/navigate the camera, X would disappear. Increasing z value slightly doesn't seem to work, I had to increase the value quite drastically, which makes it very messy. Is there a proper way to keep X always above B, after I move the camera ? Thanks !