How to create this kind of mirror texture effect?

In that case the texture still seems to be moving a bit too fast, I’ve come up with another potential solution though - just applying the texture to a standard BoxGeometry and then offsetting it inside the render loop, that way I can control it’s speed aswell as it’s direction. The problem is that the with a BoxBufferGeometry the texture seems to get applied to every side individually, whereas I need all the horizontal sides to “share” a single one if that makes sense. What’s the optimal way of achieving that?

Edit: Also yes, I realize it’s not a mirror, just didn’t know what else to call it :^)