To begin this section, we want to first define measurement and what exactly we will measure in the context of Unreal Engine 4. In a general sense, the definition of measurement is determining the size, length, or the amount of something (such as distance), the length/width/height of an object, or the volume of a particular space. In the context of Unreal Engine 4, we will measure the lengths of each component of a 3D vector in the 3D space and the X, Y, and Z dimensions. For the 2D game world, we will measure the X and Y axes. In the real world, we can use the U.S. Standard and the European Standard units of measurement to measure distance.

In the U.S., we can use the standard of lengths that involve the use of inches (in), feet (ft), yards (yd), and miles, whereas in Europe, there is the standard of lengths in place that includes millimeters (mm), centimeters (cm), meters (m), and kilometer (km). For our convenience and as a point of reference, here are a set of conversion charts between the U.S. and the European units of measurements. For more conversions, refer to this free conversion website at http://converter.eu/length/.

The following table shows the U.S. Conversions:

The following table shows the European Conversions:

The following table shows U.S. to European Conversions:

Now that we have a strong understanding of the real-world units of measurement, we are now ready to discuss how Unreal Engine 4 uses these units of measurement to determine distances and sizes of objects.

Back in the days of the UDK or Unreal Engine 3, the units of measurement were based on what was called Unreal Units (uu), where one uu equaled 0.75 in, or 16 units equaled 1 ft. In Unreal Engine 4, the measurement has changed to where 1 uu is equal to 1 cm by default, but the engine allows you to change the conversion ratio between an Unreal Unit and a meter in its World settings, as shown in the following screenshot:

The value of 100.0 in this property equates an Unreal Unit to 1 cm. For example, by changing the World to Meters property to the value of 1 (as shown before), it will equate 1 uu to 1 m and a value of 1,000 will result in 1 uu equaling 1 mm. For the purposes of this project, we will leave the default value of 100 so that an Unreal Unit will equal 1 cm, but for future reference, this is the World settings property you would want to alter in order to change this conversion ratio.

When you work on any game engine, it is very important and useful to know the common measurements that are used in your game world. Each game is different, and the scaling of that game world will be different depending on whether or not the developers are going for realistic scaling measurements, but for the purposes of this book, the following measurements will be for a game world that is going for realism. Remembering that by default, 1 uu is equal to 1 cm in Unreal Engine 4, here are some of the common measurements that you can implement in your game world. An additional note is that all the following dimensions are set under the assumption that your player character is roughly 6 ft tall or 180 uu.

The dimensions of a player character are 180(uu)H, 60(uu)W, 60(uu)D. These are dimensions for a larger character that is roughly 6 ft tall, so you may need to adjust these values accordingly based on your character's height.

The wall height is 300(uu)H to 400(uu)H. A value of 400 uu will produce a slightly taller wall, whereas a value of 300 uu will result in a slightly shorter wall, but any value between 300 uu and 400 uu will work just fine.

The wall depth (thickness)is 10(uu)D to 20(uu)D. The value of the wall thickness depends greatly on the material that the wall is made of. For example, a brick wall would be thicker than a wall made of plaster.

The dimensions of doors and doorways are 210(uu)H – 230(uu)H / 110(uu)W – 140(uu)W. The value of the door and the doorway depth (thickness) depends on the value of the wall thickness.

Staircases

The value of the staircase width will depend on the area that the staircase is placed in, so the dimensional measurement of width will vary. The following image has a step length of 30(uu)L, a step height of 15(uu)H, a step width of 200(uu)W, and 20 steps in total:

If you open a blank map in Unreal Engine 4 or the different viewports in the editor, you will notice a grid. This grid can change dynamically depending on the current unit snapping measurement applied in the editor. The spacing between each grid square will determine the number of units an object will move when you place or transform objects in the editor. Back in Unreal Engine 3 or the UDK, the grid snapping would follow the power of 2 (2/4/8/16/32/64/128/256/512/1024/2048), but in Unreal Engine 4, the grid snapping follows these values (1/5/10/50/100/500/1000/5000/10000). The main reason for this change is due to the fact that Unreal Engine 4 uses the value of an Unreal Unit equaling 1 cm instead of 1 uu equaling 0.75 in. This is similar to what it did in Unreal Engine 3 or the UDK.

By default, the unit snapping grid follows the notion that 1 uu equals 1 cm, but if we were to follow the power of 2 unit snapping scale, we have this option. In Editor Preferences under the Level Editor section, there is an option for Viewports. Under Viewports, there is a subsection labeled Grid Snapping and an option to enable/disable the Use Power of Two Snap Size, as shown in the following screenshot:

When it comes to unit snapping, follow the measurement that works best for you. Unit snapping is a very important aspect when it comes to placing assets in your game world. It can be a lifesaver when it comes to avoiding clipping or Z fighting between two objects. Unit snapping is also crucial when it comes to creating proper distances between objects, such as creating hallways or alleyways between buildings. In the end, it will save a lot of time and effort to take unit snapping into consideration at the beginning stages of level development and particularly during the white box stages of level design. There will also be specific instances when placing objects in our game world where unit snapping is not necessary, such as placing debris on the ground, placing paper on a desk, or any other objects that don't require specific distances between themselves and other in-game objects. When it comes to these instances, Unreal Engine 4 gives us the ability to toggle unit snapping on and off by clicking on the grid icon, as shown in the following screenshot. Lastly, we can also snap our objects to the grid or the floor of our environment by pressing the End key. Alternatively, we can press Ctrl + End to snap an actor to the grid. If we ever need to change the key bindings for these actions, we can navigate to the Edit Menu | Editor Preferences | Keyboard Shortcuts to make any changes.

For both character and environmental artists, it is very important to know how to change the units of measurement in the third-party 3D modeling so that when assets are exported from the art program and then imported to Unreal Engine 4, the scale is correct and as intended by the artist. Keeping in mind that Unreal Engine 4 uses the measurement conversion of 1 uu equaling 1 cm by default, we want to make sure that the units of measurement in our 3D art program uses the same conversion.

To change the units of measurement in 3ds Max (2013 version), select the Customize option and then Units Setup. Here, click on the System Unit Setup button and change the units of measurement as follows:

In Maya, we can change the units of measurement by clicking on Window from the toolbar. Now, select Settings/Preferences from the drop-down window and then Preferences. In the Preferences dialogue box, select Settings. Under Working Units, we can change the linear units to centimeter.

In this section, you learned about the basic unit conversions between the U.S. and European units and how these units translate into Unreal Engine 4's Unreal Units. Additionally, we briefly discussed the common measurements for our game world for our player character, walls, staircases, and doors/doorways. Moreover, we took an in-depth look at unit snapping in Unreal Engine 4 and the significance of the tool when it comes to object placement and creating our game world. Lastly, we looked at how to convert or change the units of measurement in 3D art programs, such as 3ds Max and Maya so that artists can ensure that their models are exported and imported to the correct scale when placed in Unreal Engine 4.

Now that we have a better understanding of the units of measurement and how they translate into Unreal Engine 4, we can now move forward to briefly discuss scientific notation.

This is a method in which we can easily write very large or significantly small numbers without having to express the entire length of the number, meaning writing a bunch of zeroes. The use of scientific notation is not very common when you use Unreal Engine 4 as a designer or an artist, but as a programmer or a technical designer who uses blueprints or even C++ coding in the engine, the use of scientific notation can deem itself useful.

Let's take a look at some examples of both large and small numbers that are expressed in their scientific notation. To keep things as simple as possible, these examples will use the base of 10 for ease of clarity:

The main logic behind using scientific notation is to take a very large or small number and convert it to an easy to read/write expression. For an example that isn't a power of 10, the number 0.5 converted to scientific notation would read as 5 * 10^-1. We reached this expression by moving the decimal point in 0.5 once to the right-hand side making the number into 5. The goal of using scientific notation is to reach the base number, meaning a number between 1 and 9. As we had to move the decimal point to the right-hand side, we know that the expression would read as a negative exponent, whereas if we were to move the decimal point to the left-hand side, the exponent would be positive. The number 5 is our base, and we multiply it by 10 with an exponent that is equal to the number of times we moved the decimal point to reach the said base. In our case, it would be 1. Lastly, we know that the exponent would be negative because we are dealing with 0.5, a number less than 1, and we had to move the decimal point to the right-hand side. As a result, our scientific notation of 0.5 would be 5 * 10^-1. Here are a few more examples of large and small numbers as expressed in the scientific notation: