PBRT

• PBRT book - ​http://www.pbrt.org/
• ​https://github.com/mmp/pbrt-v3/ -- PBRT book code v3
• ​https://github.com/mmp/pbrt-v2/ -- PBRT book code v2

• pbr intro ​http://www.codinglabs.net/article_physically_based_rendering.aspx
• pbr-cook-torrance ​http://www.codinglabs.net/article_physically_based_rendering_cook_torrance.aspx