@Japhy When “Universal Construction Planes” is active, the isometric view—unlike the perspective view—also changes my camera and point of view: it switches to an orthographic view.
I think we’ve finally reached the root of the problem. I’m forced to go into the viewport dropdown and reset the isometric view every time. Now it’s clear where the issue comes from.
However, this behavior is wrong. If it’s designed this way, it doesn’t make sense: as shown in the video, I have to reset the isometric view every time because it gets forced into a “Parallel” view (you can see it directly from the viewport name).
I should be changing the CPlane, not the focus of my view or the camera. If this logic were correct, then it should behave the same way in the perspective view as well. Instead, the perspective viewport keeps the camera fixed and only changes the CPlane.
So yes, this is exactly the issue I’m experiencing. Thanks. @davidcockey
Another factor that others might not notice during testing is that I have both viewports open at the same time—both isometric and perspective. So if someone is using Rhino with the default four views and tries to understand the issue by manually switching the perspective viewport to isometric, but doesn’t have both viewports visible simultaneously like I do, they won’t be able to reproduce the problem.
