Light Portal - Arnold User Guide

without light portal (skydome light only)	with light portal

Skydome lights can use light portals to reduce noise for interior scenes, where the light comes in through relatively small openings. Instead of emitting light, they can be used to guide Skydome Light sampling. Light portals must be placed to cover all windows, doors, and other openings through which skydome light comes into the scene.

The Skydome Light also has a Portal Mode parameter with options Off, Interior Only and Interior Exterior to respectively turn off portals, block any light outside portals for interior only scenes, and let light outside portals through for mixed interior and exterior scenes. Blocking light outside portals more predictably reduces noise for interior-only scenes.

The light portal should be oriented so that it is pointing in through the window as indicated below:

_{Light portal pointing inwards, outside window}

A simple scene that demonstrates a light portal can be found here.