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What is Global Illumination?

Exploring Environment Lighting Settings

Exploring Color Based Options

Conclusion

Configuring Global Environment Lighting Settings - Unity 2019.4

Lighting in Unity is not governed solely by lights placed in the scene, but also by Global Illumination (GI), which includes light that bounces from one surface onto another.  In this tutorial, you'll learn how to configure Global Illumination to get realistic lighting effects for your projects.

Global Illumination (2019.1)

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This tutorial has been verified using Unity 2019 LTS

Lighting in Unity is not governed solely by lights placed in the Scene, but also by Global Illumination. Global Illumination (GI) is a series of algorithms that calculate direct and indirect lighting: light that originates from a light source, and light that has bounced from one surface onto another. Unity allows the user to fine tune GI and other settings through the Lighting window. Configuring these parameters allows designers to create dramatically different lighting scenarios, from realistic to highly stylized, with just a few clicks. 

The Lighting Settings window can be found under Window > Rendering > Lighting Settings.

The first section of the Lighting Settings window manages the settings for the Scene’s Skybox, ambient lighting, and reflections (Figure 01).
 

When a new Scene is created in Unity, it comes with a Directional Light and a Default-Skybox assigned. The Directional Light serves as the Skybox’s sun, and as it is rotated in the Scene, the representation of the sun in the Skybox updates with the movement. The Skybox Material option determines what Skybox is visible in the Scene. If a procedural Skybox is being used (such as the Default Skybox), Unity will automatically link the first directional light it finds in the Scene to the Skybox’s sun. If another directional light should be used for this function, it must be added to the Sun Source option.

The Environment Lighting section controls the ambient light present in the Scene. While individual light sources such as the Default Directional Light are primary contributors to the lighting in the Scene, the Skybox contributes some level of lighting as well. If the Directional Light is disabled from the default Scene, the ambient lighting effects from the Skybox become plainly visible. To see this in practice, add a cube to the Scene by clicking on the GameObject dropdown and selecting 3D Object > Cube (Figure 02).


The Environment Lighting Source is set to the Skybox by default and will take ambient lighting information from it. If the cube is not lit up make sure in Window > Rendering > Lighting Settings you turn on Auto-Generate. This is particularly helpful if a custom Skybox is being used that is created with an HDR (High Dynamic Range) image. A HDR image-based Skybox will provide complex and realistic lighting information that replicates the environment it was originally taken from. (Figure 03).

Figure 03: The same scene with a HDR Skybox applied. Note that even with the Directional Light still disabled, the cube is brightly lit.

Figure 01: The Environment section of the Lighting settings.

Figure 02: The scene with the Directional Light disabled. Note that while it is much darker than usual, the cube is still fully visible and is receiving different levels of light on each face.

The Environment Lighting source has two other color-based options: Gradient and Color (Figure 04).

These color-based options allow the user to define a three color gradient or single color ambient light, which can give a more stylized look to a Scene (Figure 05).

The Skybox option for Source comes with a paired Intensity Multiplier. This can increase or decrease the strength of the ambient light. The default value is 1, which for most applications, is ideal, while a value of 0 will show the minimum light value produced by the skybox. Increasing the Intensity Multiplier will brighten the Scene, but note that after a point, the light will become overblown and make everything in the Scene appear washed out (Figure 06).

The final option that is shared by all three Source types is the Ambient Mode. This defines which lighting mode (whether realtime or baked) should be taken into account when calculating ambient light. If only Realtime or Mixed lighting is selected further down in the Lighting options, this mode selection will not be available.

Figure 04: The three source options.

Figure 05: A three color gradient set as the Environment Light Source. A sphere has been added to the Scene to more easily show the gradient effect. As with the cube, the sphere has no texture, so all color is coming from the gradient ambient lighting.

Figure 06: The Cube Scene with an Intensity Multiplier of 2.69. The light is so overblown that the Cube has lost its definition and appears only as a silhouette.

In this tutorial, we learned all about how to configure Global Illumination (GI) lighting settings. You learned where the lighting settings window could be found, about directional lights and procedural skyboxes, ambient lighting, and HDR (High Dynamic Range) skyboxes. With the knowledge you learned here you can take your projects to the next level and use Global Illumination to create the best lighting for your project.

Configuring Global Environment Lighting Settings - Unity 2019.4

1. What is Global Illumination?

2. Exploring Environment Lighting Settings

3. Exploring Color Based Options

4. Conclusion

Complete this tutorial