"Just a quick comparison of the Tessellation setting, at OFF vs ULTRA, on a Desert Planet (dusty, dry).

As can be seen, the Tessellation adds height/depth to the textures [the ‘pictures on the shapes of things’] of the land around the player.
It does not look “bad” at all without Tessellation though [in my opinion, as the skillful artwork makes things like the ‘sand-dunes’ (ridges of sand) look as though they have ‘height’ even without Tessellation being enabled.
The setting adds additional geometry [shapes] to the scene, which is why it demands more processing horsepower though, to display. If you are finding the game stuttering all the time, especially when traversing a Planet surface; try turning Tessellation OFF.
Personally, I find I have to do it on certain planets regardless. I still enjoy them even without the additional shaping – kudos to the artists/developers on this game!

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