Gooch shading
File:Bunny With Gooch Shading.png]]
{{short description|Non-photorealistic rendering technique}}
File:Gooch Shading applied to seashell graphics complex in Mathematica.svg
Gooch shading is a non-photorealistic rendering technique for shading objects. It is also known as "cool to warm" shading, and is widely used in technical illustration.
History
Gooch shading was developed by Amy Gooch et al. at the University of Utah School of Computing and first presented at the 1998 SIGGRAPH conference.{{cite book|author1=Amy Ashurst Gooch|author2=Bruce Gooch|author3=Peter Shirley|author4=Elaine Cohen|title=Proceedings of the 25th annual conference on Computer graphics and interactive techniques - SIGGRAPH '98 |chapter=A non-photorealistic lighting model for automatic technical illustration |author4-link=Elaine Cohen|date=1 January 1998|pages=[https://archive.org/details/computergraphics1998sigg/page/447 447–452]|doi=10.1145/280814.280950|chapter-url=https://archive.org/details/computergraphics1998sigg/page/447|accessdate=6 May 2017|publisher=ACM|isbn=978-0897919999|citeseerx=10.1.1.46.6762|s2cid=1411270 }}{{cite web|last1=Porcino|first1=Nick|title=Siggraph 1998|url=http://nickporcino.com/meshula-net-archive/posts/post138.html|website=nickporcino.com|accessdate=13 May 2017|language=en|date=10 November 2007}} It has since been implemented in shader libraries, software, and games released by Autodesk, NVIDIA, and Valve.{{cite web|title=NVIDIA Shader Library|url=http://developer.download.nvidia.com/shaderlibrary/webpages/shader_library.html|website=NVIDIA Developer Zone|publisher=NVIDIA|accessdate=6 May 2017}}{{cite web|title=About Shading, Highlighting and Coloring Faces {{!}} AutoCAD|url=https://knowledge.autodesk.com/support/autocad/learn-explore/caas/CloudHelp/cloudhelp/2016/ENU/AutoCAD-Core/files/GUID-C865EEE9-DF5E-4BFF-87A7-1E8130F68AC6-htm.html|website=Autodesk Knowledge Network|publisher=Autodesk|accessdate=6 May 2017}}{{cite book|last1=Mitchell|first1=Jason|last2=Francke|first2=Moby|last3=Eng|first3=Dhabih|title=Proceedings of the 5th international symposium on Non-photorealistic animation and rendering|chapter=Illustrative rendering in Team Fortress 2|date=1 January 2007|pages=71–76|doi=10.1145/1274871.1274883|url=http://www.valvesoftware.com/publications/2007/NPAR07_IllustrativeRenderingInTeamFortress2.pdf|accessdate=6 May 2017|publisher=ACM|isbn=9781595936240|s2cid=13002059|archive-date=12 March 2012|archive-url=https://web.archive.org/web/20120312014220/http://www.valvesoftware.com/publications/2007/NPAR2007_IllustrativeRenderingInTeamFortress2.wmv|url-status=dead}}
Process
Gooch shading defines an additional two colors in conjunction with the original model color: a warm color (such as yellow) and a cool color (such as blue). The warm color indicates surfaces that are facing toward the light source while the cool color indicates surfaces facing away. This allows shading to occur only in mid-tones so that edge lines and highlights remain visually prominent. The Gooch shader is typically implemented in two passes: all objects in the scene are first drawn with the "cool to warm" shading, and in the second pass the object’s edges are rendered in black.