In this demo the masks (vectors) change shape as they move over the images.
As to your specific example one would need to animate the image in the opposite direction of the mask movement in the same time duration to appear to not move.
Huuuuh. In Edge Animate there were two different techniques to very simply animate the ‘mask’. One of them was even called ‘Clipping’. Many years later I wonder why it is not possible in Hype Pro.
Hype Clippath does just that. The problem was and is Internet Explorer. Clipping is not supported by that browsers. Since, Microsoft now contributes to Chromium browser development and is switching the future is brigther.