If you’re new to working with (or making content for) the Unreal Engine, there is a lot of up-front information you’ll need to know before you get too far into production. One of these ‘must-haves’ is a solid grasp of how the engine defines its units of measurement.
Unreal Engine 4 uses the Metric System and centimeters as its default unit for measuring distance/length. This is a departure from previous iterations of the engine where one ‘Unreal Unit’ (or ‘uu’) is .75 of an inch. Unreal Unit size can be changed in the project settings.
Having a practical understanding of how scale and measurement works inside the Unreal Engine (or any game engine, really) is more than just a numbers game. Whether you’re creating art or programming game logic, it’s important to get a feel for the space and be familiar with the tools at your disposal. This is especially true if you’re using other external software packages like Blender or Maya, which have their own measurement/scale settings.
Before we have a look at those, let’s define a few terms.
The Unreal Unit
An Unreal Unit is a generic term used to describe the unit that the engine uses to calculate a range of measurements – including distance, time, velocity, and more. This can be different from project to project, so it’s important not to assume that 1uu will be the same when migrating objects between them.
This table shows the default values for Unreal Units across the engine’s different types of measurement.
|Type of Measurement||Unreal Unit size|
|Time||Seconds / Minutes|
|Speed/Velocity||Meters Per Second|
The most common type of measurement you’ll likely be working with is distance/length. For reference, here are some quick conversions between common units of distance measurement and the default Unreal Unit.
|Distance||Distance in default Unreal Units|
|1 centimeter||1 unreal unit|
|1 meter||100 unreal units|
|1 kilometer||100,000 unreal units|
|1 inch||2.54 unreal units|
|1 yard||91.44 unreal units|
|1 mile||160,934 unreal units|
Changing Unreal Unit size
There are several ways to change the size of the Unreal Unit. The most common (and most practical) is via the project settings. Under the Editor heading is an ‘Appearance’ section, which contains two checkboxes and several dropdowns. These let you change the unit size for each type of measurement separately.
The two checkboxes at the top will tell Unreal how you would like your values displayed. By checking them both you’ll be able to always see what units you’re working in. By default it will only show them where applicable, and not on any component transforms. I like to keep them both checked.
You can change the size of your project’s uu by selecting a new measurement from the dropdown menus. You can pick from a range of common sizes in both Metric and Imperial systems.
These settings can also be changed directly in the DefaultEditor.ini file, which can be found in your project’s config folder.
One limitation to these settings is that the engine doesn’t allow you to define your Unreal Unit size with just any arbitrary number. This means that if you wanted to experience what it was like working in the Unreal Development Kit and set your uu distance to .75 of an inch, you’re out of luck.
To be fair, this is probably for your own good.
Side Note: You should think carefully before moving away from the default Unreal Unit size. Centimeters work best for your average project, and a lot of the default values throughout the engine expect you to be operating in centimeters. If there is a scale mismatch in your art pipeline I would highly recommend tailoring your other software to match Unreal, if at all possible.
That said, changing to a different unit of scale may be completely justified. You’d know your project better than me. Just know what you’re getting into when you stray from the default settings.
Adjusting unit size in VR
The consequences for irregular or incorrect scale are far more significant in a virtual reality project. Mismatches in the dimensions of your world can cause severe motion sickness and dizziness in your players. Moreover, when looking at your game world in VR it’s far easier to notice when/where the scale is incorrect. Depth perception makes the discrepancies obvious.
Therefore, if you’re developing your project for VR you’ll want to know about an important parameter in your map’s world settings called ‘World to Meters’. Altering this setting is an easy way to globally scale the world in relation to your player.
By default, World to Meters is set to 100 as it expects the project to be using centimeters, and therefore 100uu in a meter. If you wanted to half the apparent size of the player in relation to their world, you would set this value to 50. The smaller the number, the smaller the player will appear to be.
World to Meters can also be set at runtime to make the player grow/shrink, but be careful. Playing with this setting can quickly make your players feel sick!
Adjusting your grid settings
The grid is a marvelous tool to quickly check the distances between objects. Unfortunately, unlike the details panel, it won’t update when the size of your project’s Unreal Unit is altered. This means that even if your project is set to meters – your grid will still operate in centimeters. This can naturally cause a lot of confusion.
Inside your Editor Preferences, the Viewports menu includes a section on Grid Snapping which will give you a little more control. This includes options to set the snap divisions for translation, rotation, and scale.
The restrictive design of the grid is indicative of Epic’s intention that most Unreal Engine projects will use the centimeter as their standard unit of distance.
The Measuring Tool
One feature that isn’t mentioned a lot, but one that can prove invaluable (especially to level designers), is the Measuring Tool. Although it only works in the orthographic camera views (which are accessed by clicking the two overlapping rectangles button in the top-right of your viewport), it can be used to draw a temporary line between two points on the grid to quickly and easily find the distance between them.
To use the Measuring Tool, middle-mouse click anywhere in the viewport and drag your cursor to draw a line. Your cursor will automatically snap to the nearest point on your grid.
The Measuring Tool inexplicably uses an entirely separate unit of measurement to your project’s Unreal Unit size. By default it is set to centimeters, but you can change it to meters or kilometers in the Editor Preferences, under the Viewports/Look and Feel subheading.
Common size recommendations
Here are some examples of the default size of common actors that you’ll find in the engine’s project templates and starter content. You can change these of course – every game is different – but they provide a good indication of the kind of scale Unreal expects out of the box.
|Static Mesh Plane||100cm2|
|Static Mesh Cube||100cm3|
|Third Person Character||192cm|
Giving developers the freedom to define their own space inside Unreal is a popular field for those in the community creating editor tools. There are many plugins and asset packs out there that will open up further functionality that can help you create your levels. Here are some I’ve found useful or educational.
There are several tools on the marketplace for measuring the distance between objects, and a lot of the time they try to overcomplicate things with too much information. I like the Distance Measuring Tool because it’s fast, simple, and doesn’t get in the way.
A more comprehensive package that has a lot of features for level designers, including layout, scaling and measurement tools. Overall the package is quite an overhaul of your default editor environment, but if you’re serious about level design or environment art it’s worth checking out. It’s free, after all!
If you’re at all interested in making your own level-design tools to speed up your workflow (and if you’re into technical art, I hope you will be!) this is a really good area to start.
Mapping the distance between two objects or the length of a spline both serve as a great introduction to Blueprint, Unreal’s visual scripting language. If you’re keen to learn more about this area, have a look at my tutorial on how to create your own distance measurement tool.
I hope this guide has helped you understand how scale and measurement work inside Unreal. Here are a few final tips or tricks which may come in handy.
- Irrespective of the scale of your Unreal Unit, you can move objects in the details panel with any unit of measurement you like. All you need to do is type it into the text field and Unreal will translate it for you. Super useful.
- When it comes to scale in level design, it’s important to regularly view your objects from the perspective of your player. If you’re making a first-person game for example, there is no point making things feel appropriate from any other perspective but looking through the eyes of your character.
- Playtest. All the time. Especially if you’re making anything for VR. It’s the only way you’ll know for sure if your scale feels correct.