knowledge of the definition that cel-shade falls under..
Indeed, you need to know what a
dot product is....
In order to cel shade an N64 game, you ned to realize it's not actually cel shaded. True cel shading almost always requires the use of an edge detection filter, which n64 cannot utilize.
Well, to do that, you need pixel shaders..Which is something the N64 isnt capable of.
I guess I think of cell shade as the way the light appears and the solid colors.
Correct! Cel shading algorithms always take into account the light, when using the dot product to calculate light values. From there, thats how we get the distinctive cel shaded lighting effects (think LOZ: Wind Waker for a perfect example).
Cel shading is a method of rendering a three dimensional model so that it looks like a hand-drawn animation cel, rather than a photorealistic rendering. It does this by reducing the total number of colors from smooth (phong or gouraud shaded, etc.) to a user-selected palette, and accentuating the model's borders and lines. A good cel shading algorithm's end product is an extremely convincing cartoon look, which is indistinguishable from a traditional artist's work unless you know exactly what to look for.
Color range replacement is the key to cel shading, and making a palette with enough of the right colors will insure a good looking result. Before any cel shading is done, shader renders the entire scene using normal shading and taking the usual amount of processor time. Then the shader analyses the image with a user-defined table that lists ranges of color to replace with a single color. That is, any pixel between within a certain range of color, light to dark red for instance, is replaced with a pixel of a single color from the palette, say a medium red. In the end, all of the smooth fades and gradients that would make the image look "3D" are replaced with blocks of two or three shades, which make the entire scene look like it was colored by hand.