Ai Skydome Light


Simulates light from a hemisphere or dome above the scene, representing the sky. Can also be used with high dynamic range (HDR) images to perform image-based environment lighting. This is the node which is typically used for lighting exterior scenes. 

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 Skydome lighting.


When using Color Management in Maya (2017), HDR maps should be set to RAW. More information can be found here.

A tutorial that uses the Ai Skydome light can be found here.

 

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 increase 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. 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

Camera

By default, skydome lights 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 Diffuse, Specular, SSS, and Volume. Weights scaling the light contribution to each of those components independently. Should be left at 1 to produce physically accurate results.

 

Viewport

Note that 'Hardware Texturing' in Maya's viewport will only work when using a Maya file texture with the Ai Skydome light. Using an 'Ai Image,' for example, will return black in the viewport.

Sky Radius

The size of the sky in the Maya viewport.

Facing

The direction that the Color texture map faces in the viewport. Can be set to Front, Back or Both.

 

 

Currently, the Ai SkyDome light will not appear in the light linking window. A workaround is to use the defaultLightSet to change light linking options for Arnold lights (make sure to refresh the IPR when making changes in the light linking window).

A video demonstrating this process can be found here.

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.

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