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SIGGRAPH course 2016: An Artist-Friendly Workflow for Panoramic HDRI

Image-based lighting (IBL) with high dynamic range images (HDRI) is a well-known concept in the VFX and videogame industries, since Paul Debevec’s SIGGRAPH’97 paper that popularized the technique. Panoramic HDRI as a lighting source allows one to easily reproduce lighting from the real world and to better integrate a CG object inside an environment—a technique that’s widely used today.

With the current interest in physically based rendering (PBR), there is a growing need for accurate HDRI creation to use them as a light source. An accurate HDRI:

• captures the full range of lighting in the scene, without clipping

• has minimal lens artifacts

• is linear

• doesn’t include any artistic effects

In addition to the above requirements, we want to be able to recover the real-world intensity of an HDRI’s texels. Combined with physical light units, this allows us to use panoramic HDRIs and virtual lights together, with the correct lighting ratio. This ratio is usually eye-balled by artists. This document is oriented toward artists and describes an artist-friendly workflow for producing and using accurate HDRIs with the best practices we found when shooting our own HDRIs for Unity. For this workflow, we have avoided using complex devices or building a custom setup, so as many artists as possible will be able to reproduce our steps.

The slides notes and source code are available here