Physically Based Rendering in Filament

Summary

**Physically Based Rendering in Filament**  # About This document is part of the [Filament project](https://github.com/google/filament). To report errors in this document please use the [project's issue tracker](https://github.com/google/filament/issues). ## Authors - [Romain Guy](https://github.com/romainguy), [@romainguy](https://twitter.com/romainguy) - [Mathias Agopian](https://github.com/pixelflinger), [@darthmoosious](https://twitter.com/darthmoosious) # Overview Filament is a physically based rendering (PBR) engine for Android. The goal of Filament is to offer a set of tools and APIs for Android developers that will enable them to create high quality 2D and 3D rendering with ease. The goal of this document is to explain the equations and theory behind the material and lighting models used in Filament. This document is intended as a reference for contributors to Filament or developers interested in the inner workings of the engine. We will provide code snippets as needed to make the relationship between theory and practice as clear as possible. This document is not intended as a design document. It focuses solely on algorithms and its content could be used to implement PBR in any engine. However, this document explains why we chose specific algorithms/models over others. Unless noted otherwise, all the 3D renderings present in this document have been generated in-engine (prototype or production). Many of these 3D renderings were captured during the early stages of development of Filament and do not reflect the final quality. ## Principles Real-time rendering is an active area of research and there is a large number of equations, algorithms and implementation to choose from for every single feature that needs to be implemented (the book *Rendering real-time shadows*, for instance, is a 400 pages summary of dozens of shadows rendering techniques). As such, we must first define our goals (or principles, to follow Brent Burley's semina...