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  • Writer's pictureLingheng Tao

UE#4 Lighting - Part 1 Directional Light

4.0 Introduction

This note writes about some basic concepts of lighting adjustments in Unreal Engine 4.

The material I used in this note is the Abandoned Factory from RonaldHoutermans.

We proceed with analysing how the artist finished the lights and post process of this scene.

Fortunately, the artist has put all the related components in the folder Lights&PostProcess. This is a very good habit that we all should learn.

4.1 Directional Light

Usually, we will have a directional light function as the main lighting source in a scene. It could be find in the Place Actors > Lights > Directional Light.

This is the level with directional light (01_Sun_Light Source) on constrast by turning off it.

With Directional Light On
With Directional Light Off

It is quite easy to see the difference. The directional light is usually used as the sun in a level. It marks the location, direction, and other properties of the sunlight. We will not go over all the labels and functions in this component because they are too much for lighting. We will just select some of the most important components.

4.1.1 Light

Let's first go to see the Light panel.

- Intensity: this is the intensity of the directional light. The larger the number, the brighter the light.

33.0 Lux
330.0 Lux

- Light Color : the color of the light.

- Source Angle: the angle subtended by the light source in degrees. Notice that if it is used as our sun, we should just use the default degree which is 0.5357 (as the tip said in the engine).

- Source Soft Angle: a subtle value that we hardly need to adjust.

- Temperature: if you activate the Use Temperature box, we can set the color temperature by this. Please read Wikipedia for more details about color temperature.

Specially I have put the wikipedia chart here for convenience.

So setting a temperature lower than 6500 will make the light looks closer to red/yellow.

6500K (White)

- Affect World: whether to activate the light. Usually this should be activated.

- Cast Shadows: whether the light will cast shadow. Usually this should be activated unless we need to do some stylized rendering.

- Indirect Lighting Intensity: just read the tip.

- Volumetric Scattering Intensity: intensity of the volumetric scattering, which is also known as the Tyndall effect.

VSI = 0
VSI = 10.0
VSI = 100.0

4.1.2 Rendering

Now let's go to see the rendering panel.

- Visible: disactivate this will result in disabling shadow.

- Actor Hidden In Game: simple remain it as disabled.

- Editor Billboard Scale: make the editor symbol scale larger.

The small sun symbol looks bigger.

4.1.3 Atmosphere and Cloud

The unreal engine also supports the interaction between atmosphere/cloud and directional light.

- Atmosphere Sun Light: activating it to allow the generation of the visual disk by the interaction of the directional light with the atmosphere and cloud. The activation of this box will allow the next 2 selections be able to be selected.

- Cast Shadows on Clouds: literally. Notice that if there is another directional light in the level (for example, the first, sun, and the second, the moon), and its Atmosphere Sun Light has been activated, and its Atmosphere Sun Light Index has been set as 1, this box will be disabled.

- Cast Shadows on Atmosphere: literally.

- Cast Cloud Shadows: literally.

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