I've encountered that, too, in my Excel 97 easter egg reproduction. My terrain loops in the shader, but camera position is governed by the JavaScript, so it can get weird far from origin if I don't sanitize.
Here's how the terrain normally looks, zoomed out with the grid on:
There's two weird phenomena happening there: the lack of camera position precision causes the terrain to shift left and right, but a little bit further, you can see that all the terrain quads collapse in one dimension for some reason.
Someone also made a game out of this, called Floating Point Leviathan:
Here's how the terrain normally looks, zoomed out with the grid on:
https://rezmason.github.io/excel_97_egg/?o=bq
And here's how it looks 8589990 units from the origin, with sanitizing off:
https://rezmason.github.io/excel_97_egg/?o=bq&sanitizePositi...
There's two weird phenomena happening there: the lack of camera position precision causes the terrain to shift left and right, but a little bit further, you can see that all the terrain quads collapse in one dimension for some reason.
Someone also made a game out of this, called Floating Point Leviathan:
https://yanknoopdev.itch.io/fpl