Game Programming using Qt 5 Beginner's Guide - Second Edition

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The ParallaxScene element we implemented is a moving plane. Its horizontal offset depends on the character's current position and the size of the view. The range of scroll of the scene is determined by the difference between the scene size and the view size—it says how much scrolling we have to do when the character moves from the left edge to the right edge of the scene so that it is in view all the time. If we multiply that by the distance of the character from the left edge of the scene expressed as a fraction of the scene width, we will get the needed scene offset in the view (or otherwise speaking, a projection offset of the scene).

The second type—ParallaxLayer—is also a moving plane. It defines a distance factor ...