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From: Jeff Dicker <jadic...@cgl.uwaterloo.ca>
Newsgroups: uw.cs.cs488
Subject: Re: Team Fortress 2 Character Lighting
Date: Thu, 13 Mar 2008 20:34:22 -0400
Organization: University of Waterloo
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I'm immediately struck with a couple of comments about this with respect 
to the projects:

1) Note how much better the Heavy model looks because of phong shading. 
  There were a couple of final ray traced scenes that could have 
benefited greatly from phong shading (though it was not required!). 
Thanks to phong shading, the model appears to be smooth despite not 
having a particularly large number of polygons (you can see the 
tesolation).  Implementing this in a shader (usually known as per-pixel 
shading, since more values than normals may be interpolated) is trivial, 
and it's also not hard to implement in a ray tracer.

2) If you are working on an OpenGL project and planning on implementing 
shaders, TF2 style shading is quite possible.  As Andrew pointed out, 
n.l and r.v are the basic keys to diffuse and specular shading - making 
the tweaks Valve did, like a half-lambertian lighting term, should be as 
easy as passing a couple more variables to the shader.  Some parts are 
trickier, like the 2D toon-shading lookup, but if you're looking to get 
some subjective marks those slides could be helpful!

-Jeff

Andrew Scherkus wrote:
> Just thought some of you might find this presentation from the Game 
> Developers Conference really interesting.  In summary, the makers of Team
> Fortress 2 describe the art style of the game and how they developed 
> shading
> and lighting models to replicate the style of early 20th century commercial
> illustrator J.C. Leyendecker.
> 
> Of particular interest are slides 27-58 where they break down every 
> piece of both the view-independent and view-depenedent character 
> lighting equations.  You might be surprised at how many of the lighting 
> equations used in A4 show up...
> 
> http://www.valvesoftware.com/publications/2008/GDC2008_StylizationWithAPurpose_TF2.pdf 
> 
> 
> Andrew