What is Smooth Terrain?
Smooth terrain is a useful feature of Roblox that allows you to easily create beautiful looking terrain such as what you see in the picture above. It is a very powerful tool that can greatly enhance the look of your game to make it really shine.
Where do I get Started?
There are two places where you can find the tools you will need to work with smooth terrain. The first place you can find your tools is on the Home tab at the top of studio:
There is also a Terrain tab that is specifically for terrain and it also includes 1 extra tool that is not visible on the Home tab:
What do All These Tools Do?
This is where the fun begins 
Each tool will have it’s own unique mini-menu that will appear in the upper left-hand corner of your workspace where you can customize and tailor some tool properties to suit your building needs. In the picture below you can see the mini-menu for the generator tool.
Generate Tool
The generate tool is just that, a terrain generator. However, you do have a lot of control over the terrain that it generates. At the very top you can set your map size in voxels which are individual areas that are about 4x4x4 studs in size. Right below that you can enter a seed for your generator, by default this number is the place ID of the place you are working in. Next are Caves. If you select this box it will generate caves and tunnels underground in your map. The last two selections, Biome Size and Biomes, work together. Under Biomes you can select and mix and match from a list of biomes that you can generate in your map. Biome types include:
- Water
- Marsh
- Plains
- Hills
- Dunes
- Canyons
- Mountains
- Lavascape
- Arctic
The Biome Size selector is to select about how large the biomes will be. So if you want a lot of biomes close together you would select a smaller biome size than if you were trying to generate a large sprawling map.
Generator Tool Menu
What you can create with the generator with plains, hills, canyons, and mountains.
Add Tool
The add tool allows you to quickly create chunks of terrain and is very useful for rough blocking a map and for creating vertical walls of terrain. As you can see from the picture below, you can easily set the size and shape of your “brush” depending on what you are trying to accomplish. The strength doesn’t matter so don’t worry about it. At the bottom you can see a visual of all the types of terrain that you can use and there is also an Auto selection that will simply create the same type of terrain as what’s around it. In the middle there are two selections, Snap to Grid and Ignore Water. Snap to grid simply aligns your tool with a voxel grid and ignore water will leave water terrain alone when you add terrain around or in it.
Add tool menu
Add tool in action
Subtract Tool
This tool works the same as the add tool but removes terrain instead of adding it.
Subtract tool menu
Paint Tool
The paint tool paints a particular terrain type over other terrains without adding or removing any terrain. This tool is useful for adding small details to terrain and the finishing touches like a painting a path or painting over that little bit of terrain that should be a different material. The plain lock selection in the middle allows you to lock onto a particular plane and only paint the terrain along that plain which could be useful for things like painting layers of matieral in a canyon.
Paint tool menu
Paint tool being used to create a dirt path
Grow Tool
The grow tool is similar to the add tool but it doesn’t instantly add terrain, instead it grows the terrain where you click. In the case of this tool, the strength slider does work and it determines how quickly it will grow terrain. Small strength is useful for making small adjustments to terrain while a lot of strength can be useful when filling in large areas.
Grow tool menu
Growing terrain into arches!
Erode Tool
Works just like the grow tool but in reverse! This tool is very useful for hollowing out areas for lakes and rivers and for carving tunnels and caves.
Erode tool menu
Erode tool in action creating a tunnel
Smooth Tool
The smooth tool allows you to smooth out an uneven area of terrain.
Smooth tool menu
Smooth tool being used to smooth out an area between two strips of terrain.
Regions Tool
The regions tool gives you the ability to manipulate terrain sections similar to parts. With it, you could select an area, copy and then paste it, and then move, resize, and/or rotate the selected terrain.
Regions tool menu
Region tool in use
Smooth Terrain Tips and Tricks
These are a couple useful tricks that I have discovered to make my smooth terrain creations look better
Better Smoothing
Sometimes the smooth tool will smooth the terrain but at the same time it will leave ridges as can be seen in this picture:
I have found that an excellent way to fix this is to either grow or erode that area while the strength of the tool is at it’s minimum or very low. While this will add or remove a thin layer of terrain it will look a lot better as seen in this picture here:
Merging Terrain Types
This also uses the grow tool. The method here is that where two terrain types meet you grow the opposite terrain type on either side to make the transition gradual. Example: You have a sandy spot with grass right next to it. Select sand and grow it on low strength on the grass. Then do the same thing with grass on the sand so you end up with something like this:
Here is an example of it being used on a larger scale:
Converting Parts into Terrain Using Scripting
Sometimes you need to fill in a specific area with terrain or you want a nice flat piece of terrain that would be extremely hard to build by hand. Have no fear! This problem can be solved with some simple scripting knowledge and the command bar. If you don’t know what the command bar is, it’s a place where you can enter and run code without having to test your place. It looks like this and by default it is located at the very bottom of studio.
I have also put together a script with some useful code examples that you can run in the command bar.
:FillBlock()
http://wiki.roblox.com/index.php?title=API:Class/Terrain/FillBlock
Fills a block of smooth terrain with a given location, rotation, size, and material. It is useful to create terrain to fill in the area that a specified part takes up
Example code
local part = game.Workspace.Part
game.Workspace.Terrain:FillBlock(part.CFrame, part.Size, Enum.Material.Grass):FillBall()
http://wiki.roblox.com/index.php?title=API:Class/Terrain/FillBall
Works similarly to :FillBlock() but will create a ball of terrain at a specific position with a specified radius.
Example code where the position is the center of a part and the radius is half the part height.
local part = game.Workspace.Part
game.Workspace.Terrain:FillBall(part.Position, part.Size.Y/2, Enum.Material.Grass):FillRegion()
http://wiki.roblox.com/index.php?title=API:Class/Terrain/FillRegion
This will fill a Region3 space with smooth terrain.
local RegionToBeFilled = Region3.new(Vector3.new(0,0,0), Vector3.new(9,9,9))
game.Workspace.Terrain:FillRegion(RegionToBeFilled:ExpandToGrid(4),4,"Grass")That’s all I have for now, I hope this helps 
