Smooth Tool in Terrain Editor Acts Like Erode when Base Size Is Set to 1

This bug occurs in Roblox Studio when using the Terrain Editor. When the smooth tool is selected and base size is set to 1, it behaves like the erode tool at max strength, eating up the terrain quickly. The strength is not affected by this. Currently unknown when it originally began to occur, but this happens as of June 4, 2020.


  1. Open any place
  2. Create any sort of flat terrain using Generate or Add Tools
  3. Switch to Smooth
  4. Set the Base Size to 1
  5. You will see that the terrain erode quickly.

Additional Notes

Setting the Base Size to 2 may produce similar results when dragged to a certain time, while setting the Base Size to 3 or above behaves as expected. This bug affects the ability to smooth out finer details in terrain in a smaller scale.


Nope. This is done on flat terrain with no angle whatsoever.

So its flat terrain? I do not understand that. Can you tell me more description?

By Flat Terrain, I mean the starter place when you open Studio and greeted with the “New” page.

Or by this image:

I was also gonna post a bug report about this. It really bothers me when I try to smoothen out a hill and it just destroys the hill rather than smoothing it out. I can report this happening to me as well. I’m on a MacBook Pro 2017


Major support. It’s done this way because the smooth tool will make the brush look like it’s surroundings.

If the brush is near a cave’s mouth, for example, it will chip away at the mouth since the brush detects empty space. Similarly, a hole in the ground will be filled because everything around it is filled.

However, on a thin, empty expanse of terrain, the smooth tool will not create terrain because there is nothing around it that tells it to grow, and will erode since below it there is an empty expanse. It will want to emulate that.

This, for me, is especially problematic in terrain generated by a hieghtmap. It’s so thin that I can’t smooth it out.
This needs to be fixed. ○︿○

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Thanks for the report! We’ve filed this internally and we’ll follow up here when we have an update for you.


Thank you so much! It’s nice to know that feature requests are seen by staff.

Adding to the points above, when I used the new replace tool to make a platform, if ever it’s too thin, smoothing was impossible.

Terrain’s QoL is going to improve just a little more. Maybe even heightmaps will get some functionallity and realism…?

Hopefully it gets fixed quickly. (☆•◇•☆)

I have an update from our engineers. They are looking at a possible fix for this in early 2021. When there is more info I will pass it along.