Mesh Appearance Changed in Top View?

I’ve been working with a large topographic mesh for the past couple weeks on a large project. The appearance of the mesh suddenly changed in my top view, mid-work session. I have no idea why, quick online search unearthed nothing. Normally the mesh appears similar to how it does in the perspective viewport. Suddenly it changed to a sort of topographic view with distinct changes in elevation level. Still looks normal in my perspective viewport though.

I don’t even mind the appearance change that much, but I’d like to know what setting I accidentally changed or triggered. Anybody know why?

Here are some images to show what I’m talking about:

Perspective view, still normal:

Top view:

Hi - it’s very hard to tell from just those pictures. Which display mode are you using in the Top view? Is that a custom display mode or a factory-default one? Has it been changed from the defaults? Can you post the file?

I was using the default Top view. I do not recall changing any settings. The file is very large, and it wouldn’t matter much posting it - after restarting Rhino, it returned to normal. It would still be great to figure what happened though, I would like to be able to recreate that effect.