A dome light is a spherical or hemispherical light that is often paired with a high dynamic range image (HDRI) of the environment. This type of image-based environment lighting has been a staple in CG rendering for years.
Although image-based lighting has improved over the years, it still involves a lot of sampling, especially for interior scenes. Generally V-Ray samples the HDR dome efficiently to make sure that there is as little noise as possible. However light typically enters interior spaces through small openings like windows and doors and only a small portion of the dome light actually contributes to the image, making the sampling of the dome light with HDR image not very efficient.
As a workaround, you could add Skylight Portals near openings like doors, windows, and skylights that help direct light samples. But this is a manual process that takes time — and it’s not accurate.
To avoid this problem, we built a smarter dome light based on a similar concept as Adaptive Lights. Now, the new Adaptive Dome Light uses the Light Cache calculation phase to learn which parts of the dome light are most likely to affect the scene.
With the Adaptive Dome Light, Skylight Portals are no longer needed. It automatically figures out which portions of the environment to sample and which ones to ignore. This makes it much easier to set up and much more efficient.
More accurate light sampling
In this library scene by Bertrand Benoit, there’s a noticeable improvement in the global illumination. This is because the Adaptive Dome Light concentrates its efforts in the right spots making it not only more accurate, but faster as well. In some scenes you might not notice a difference in the lighting, but in scenes such as this, the difference is easy to spot.
Scene courtesy of BBB3viz
How much faster is the Adaptive Dome Light?
Many factors can affect the overall speed gains that this feature can give you. Our early tests have seen speed increases from 10% up to 700%, depending on factors such as the complexity of the scene, contrast level of the HDRI, etc. Here are a few examples of different types of HDRIs and scene types.
More information: Chaos Group Blog.
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