When building and creating your worlds and levels within the Unreal Engine, you have the ability to be able to create and use light sources as you wish. There are a number of ways to add lights and even a number of different light sources that can be used within Unreal. There are a few key properties to the lights that have the greatest impact on how you light your world. You can add light sources into your levels the same as you would add anything else into your world, you would just drag it over from the “Modes” menu there is a “Lights” tab where you would find the different types of lights that you will have access to be able to add into your world. You could also add a light source by simply right clicking on the view port and selecting “Place Actor” and then selecting the type of light source you want to add from the “Lights” category that will drop down. The first type of light source that we have available to us that we will look out is what is called the “Directional Light”, this light source is the ideal choice that you would use when you want to simulate sunlight. Directional Lights simulate light that is being emitted from a single source that is far away, this makes it so that all shadows cast by this light will be parallel. The Directional Light has three different types of Mobility settings that you can have it set to depending on what you want to use it for. You can keep the Directional Light “static” which means that the light can’t be changed in the game. The other setting that is like “static” is the “stationary” which means that the light will have its shadows and bounced lighting from static geometry baked by Lightmass, and all other lighting will be dynamic. This setting unlike the “static” allows the light to change color and intensities while in game but it still does not move. The last option for mobility that you will have for the “Directional Light” is the “moveable” setting, which means the light is completely dynamic and gives dynamic shadowing. This setting is the slowest when it comes to rendering but it gives you the most freedom and flexibility during gameplay. Another possible light source that we can use within our worlds are what is called a “Spot Light” . Which works just like a spot light where it will emit light from a single source out in a cone shape, this light source will work the same as a flash light or a spot light on a stage. The “Spot Light” light source also has three different mobility settings that can be given to them. The first mobility setting being “static” which means that the light can’t be changed within the game. “Stationary” the same as “Directional Lights” where the shadows and bounced lighting will be baked by Lightmass and other lighting will be dynamic. The third mobility option is “moveable” which means the light is totally dynamic and allows for dynamic shadowing. The other lighting option that Unreal gives us to use is called the “Point Light” , this is the light source that works exactly like a real world light bulb. This light source emits light from a single source in all directions. For simplified purposes the “Point Light” emit light equally in all directions from the single point source. The “Point Light” like the other light sources has three mobility settings as well. The first being “static” like the others it means the light can’t be changed in game. The second, “stationary” works the same as the previous light sources. The final setting is “moveable” which makes the light source completely dynamic. Those are the different light sources that can be placed within your world, apart from the mobility settings for all these light sources they each also have settings for light intensity, which determines how much energy the light source will output. When it comes to “Point Lights” or “Spot Lights” the intensity is measured in Lumens, where 1700 lumens corresponds to being as bright as a 100w lightbulb. There is also settings for light color and a setting for “Attenuation Radius”, this setting will set the reach of your light source, it will define what objects the light source will affect and it’s basically the “out of bounds” when it comes to calculating the falloff of the light. This setting can have serious impact on performance so you only want to use a large radius when it is completely necessary. There is also a “Source Radius” and “Source Length” which define the size of specular highlights on surfaces. The Unreal Engine also provides us with something called “Lighting Channels”, this is a rendering feature that enables you to choose what surfaces are lit by specific lights. Lighting Channels allow dynamic lights to only affect objects when their lighting channels overlap. The Lighting Channels are mostly used for cinematic use, so it can give you control on how Actors within your world are lit up by your light sources. In the Unreal Engine by default, directional lights, spot lights, point lights and all Actors that can be affected by lights have Lighting Channel 0 enabled. Currently Unreal can support up to 3 lighting channels. There are some limitations to using these lighting channels, their influence is applied dynamically, which means it won’t work with Static Lights or Static Mesh Actors that have static mobility. You can set your static mesh actors to a “movable” mobility setting and it will work. You will need to use either Stationary lights or Movable lights for it to work with lighting channels. Unreal Engine gives us a lot of flexibility and functionality when it comes to lighting and what we can use and what we can do with it. You can build a beautifully lit outdoor world with natural sunlight, an indoor setting with indoor lighting as well as using outdoor lighting through windows for your indoor lighting, or even create a dimly lit underground dungeon world. It can all be accomplished with the lighting tools provided to us within the Unreal Editor.