Skybox lights

Beginner Designer Programmer

A skybox light is an ambient light emitted by a skybox. Xenko analyzes the skybox cubemap and generates lighting using image-based lighting (Wikipedia).

You don't need to actually display the skybox in the scene to use it as a light source. For example, you might not want to use the skybox to light the scene if the sky is only partly visible from an interior location (eg through windows of a room). As ambient lights aren't affected by shadows, they light every part of the scene, including interior spaces.

How skyboxes light the scene

These images show the difference between ambient and skybox lighting on two pure diffuse materials:

Ambient lighting	Skybox lighting

These images show the effect of skybox lighting on a material with different metal and gloss properties:

Material Plastic	Metal 100% Gloss 50%	Metal 100% Gloss 100%

Notice how the skybox texture colors are reflected.

Set up a skybox light

To use a skybox as a light, you need to add a skybox asset, then select it in a Light component.

1. In the Asset view, click

2. Select Miscellaneous > Skybox.

   

   The Asset picker opens.

3. Choose a skybox texture (.dds file) from the project assets and click OK.

   

   Game Studio adds the skybox asset with the texture you specified.

4. Select the entity you want to be the skybox light.

5. In the Property grid (on the right by default), click Add component and select Light.

   

6. In the Light component properties, under Light, select Skybox.

   

7. Click (Pick an asset up):

   

8. Select the skybox asset you want to use as a light source and click OK.

   

The Light component uses the skybox asset to light the scene.

Skybox asset properties

When you use a skybox as a light, Xenko uses it both in compressed form (spherical harmonics (Wikipedia)) and as a texture to light different kinds of material. You can control the detail of both in the skybox asset properties.

Property	Description
Cube Map	The cubemap asset used for the skybox
Specular Only	Use the skybox only for specular lighting
Diffuse SH Order	The level of detail of the compressed skybox, used for diffuse lighting (dull materials). Order5 is more detailed than Order3
Specular Cubemap Size	The texture size used for specular lighting. Larger textures have more detail.

Skybox light properties

Property	Description
Intensity	The light intensity
Culling Mask	Which entity groups are affected by the light. By default, all groups are affected

Example code

The following code changes the skybox light and its intensity:

public Skybox skybox;
public void ChangeSkyboxParameters()
{
    // Get the light component from an entity
    var light = Entity.Get<LightComponent>();

    // Get the Skybox Light settings from the light component
    var skyboxLight = light.Type as LightSkybox;

    // Replace the existing skybox
    skyboxLight.Skybox = skybox;

    // Change the skybox light intensity
    light.Intensity = 1.5f;
}

See also

• Skyboxes