This simulates light from a sphere or dome above the scene, representing the sky. It can also be used with high dynamic range (HDR) images to perform image-based environment lighting. This is the node that is typically used for lighting exterior scenes. The Skydome Light has a texturable color slot so that you can map a texture to be used for IBL.

• The Skydome Light will not work with Atmosphere Volume. You must use regular lights that have a precise location and size, and inverse-square decay.
• This light is designed for outdoor scenes and is represented by a spherical dome in the background. Importance sampling will trace rays to specific directions of this dome. However, in an interior scene, most of these rays will hit an object, getting no contribution from the light at all and thus creating noise. In this situation, adding light portals to the windows will help to reduce noise in an interior scene when using the Skydome Light.

The lights page has more detail about the controls. The only additional attributes are:

Color

The color of the light. The Skydome Light has a texturable color slot so that you can map a texture to be used for IBL.

Intensity

Intensity controls the brightness of light emitted by the light source by multiplying the color.

Resolution

The resolution controls the detail of reflections of the skydome. For most accurate results the skydome_light resolution must be set to match the HDRI image resolution, however, in many cases it can be set lower without a noticeable loss of detail in reflections. By default, the parameter is set to 1000. The higher the resolution parameter, the longer the Skydome Light will take to precompute the importance tables for the light, which increases scene startup time.

The resolution attribute should be used with care. The higher the resolution value, the longer the Skydome Light will take to pre-compute the importance tables for that light. For high-resolution maps, this can be very slow.

Format

The type of map being connected. It can be set to Lat-long (most common), Mirrored Ball or Angular.

Portal Mode

Defines how the skydome light interacts with light portals.

• Off : turns off portals.
• Interior Only : blocks any light outside portals for interior-only scenes.
• Interior Exterior : lets light outside portals through for mixed interior and exterior scenes.

Blocking light outside portals more predictably reduces noise for interior-only scenes.

AOV Indirect

Outputs an indirect light AOV (the Skydome Light outputs to direct light AOVs by default).

Visibility

Only Area lights and Point lights (non-0 radius) are visible to the camera. Camera and Transmission values default to 0 with Area lights.

Camera

By default, Skydome Light are directly visible as a background. Lowering the influence of the light of camera rays makes them invisible to the camera, and makes the background transparent.

Transmission

Per-light scaling for Transmission. Should be left at 1 to produce physically accurate results.

Diffuse / Specular / SSS / Volume

Per-light scaling for Camera, Transmission, Diffuse, Specular, SSS, Indirect and Volume. Weights scaling the light contribution to each of those components independently. Should be left at 1 to produce physically accurate results.