pbrt-v4 makes use of the following third-party libraries and data. Thanks
to all of the developers who have made these available!

* [double-conversion](https://github.com/google/double-conversion)
* [filesystem](https://github.com/wjakob/filesystem)
* [googletest](https://github.com/google/googletest)
* [lodepng](https://lodev.org/lodepng/)
* [OpenEXR](http:://www.openexr.com)
* [Ptex](http://ptex.us/)
* [rply](http://w3.impa.br/~diego/software/rply/)
* [skymodel](https://cgg.mff.cuni.cz/projects/SkylightModelling/)
* [stb](https://github.com/nothings/stb)
* [tinyobjloader](https://github.com/tinyobjloader/tinyobjloader)
* [zlib](https://zlib.net/)

Thanks also to Anders Langlands, who provided the Sensor implementation
used in the film model and Syoyo Fujita for the cyhair converter.

pbrt-v4 also includes spectral data from the following sources:

* Glass refractive index tables from https://refractiveindex.info, public
  domain CC0.
* Camera sensor measurement data from https://github.com/ampas/rawtoaces,
  Copyright © 2017 Academy of Motion Picture Arts and Sciences.