Is there a way to "smart" auto-reduce the amount of vertices? I made a height map based on a displacement, with a very high vertex count.
However, some parts of the map are flat because the terrain actually... is flat.
I have now 1 million vertices, of which at least 80% are quite useless.

So:
I would like to mass-dissolve vertices that are:
- adjacent to each other
- same height
...so that the flat parts of the terrain would become simplified, to reduce unnecessary vertices (and thus file size and CPU effort etc)


I do want to keep the steep hills and canyons with a lot of detail of course, as you can see on the lower half of the image. It's just the flat parts I want simplified.

Is there a way to do this without doing it manually? Because that would take ages.

PS: I tried "limited dissolve" but that kills the app.

Thanks in advance.
You can select one top face, then shiftG > Select Similar > Normal, then ctrlE > Un-Subivide.



Also, you have the Decimate modifier / Planar mode that will unsubdivide all the faces on the same normal orientation, or according to a certain angle threshold, it will allow you to preserve all the details: