• To create and display an image (or picture) using
computer graphics, we need to compute the color
and intensity of the light at each point in the
content.
• For this purpose, many processes are involved:
– Viewing / Projection: determine where each object
should go in the image
– Rasterization: determine which pixels should be filled
– Visibility / Hidden surface removal: determine which
object is in front at each pixel
– Illumination / Shading: determine what color it is
§1. Introduction
5
6
• How to represent color and intensity
• How to develop illumination models to compute
color and intensity
– Light source
Color (wavelength of light)
Position, direction, …
– Object properties
Material
Geometry
Absorption
– Observer
Illumination
Outline
§1. Introduction
§2. RGB color model
§3. Light sources
§4. Empirical illumination model
§5. Computation with Phong illumination model
§6. Summary
7
• Color forms a 3D vector space.
• Three primary colors: red, green, blue.
• Every color is represented as a linear combination of red
(R), green (G) and blue (B).
• In image processing, each of R,G,B is an integer between
0 and 255
• In computer graphics, each of R,G and B is a floating-point
number between 0 and 1.
§2. RGB Color Model
8
