We implemented a simple version of ray tracing to a sphere You can see what we did in hw2.zip. I've added some comments to make things easier to read. I also mentioned the alternate open-source Tor Web Browser, which uses a search engine that doesn't track you or sell your information to advertisers. Just in case you sometimes want a less intrusive alternative to you-know-who. :-)   Then I went over Phong Shading on the whiteboard The first really interesting model for surface reflection was developed by Bui-Tong Phong in 1973. Before that, computer graphics surfaces were rendered using only diffuse lambert reflection. Phong's was the first model that accounted for specular highlights. The Phong model begins by defining a reflection vector R, which is a reflection of the direction to the light source L about the surface normal N. As we showed in class, and as you can see from the diagram on the right, it is given by: R = 2 (N • L) N - L   Computing the R vector

Once R has been defined, then the Phong model approximates the specular component of surface reflectance as: Srgb max(0, E • R)p ) where Srgb is the color of specular reflection, p is a specular power, and E is the direction to the eye. In our case, E = -W, the reverse of the ray direction. The larger the specular power p, the "shinier" the surface will appear. We can have more than one light. To get the complete Phong reflectance, we sum over the lights in the scene: Argb + ∑i lightColori ( Drgb max(0, N • Li) + Srgb max(0, E • R) p ) where Argb, Drgb and Srgb are the ambient, diffuse and specular color, respectively, and p is the specular power.   Vectors used for Phong specular reflection   Homework, due before start of class on Thursday Feb 20 Extend what I implemented in class by adding the specular component of the Phong reflectance model. When you have done that, you should see a specular highlight on the sphere. For the image on the right, I used a Phong specular power of 20.0. Some things you might try for extra credit: Try putting two or more spheres into the scene Try more than one light source Animate things creatively Put some noise texture on your sphere Add noise into the sphere computation itself You can also use your imagination, and do something for extra credit that will surprise me. I would like that. :-)   Sphere with specular component