CS488 - Introduction to Computer Graphics - Lecture 18

Comments and Questions


Review

  1. Colour

Lighting Models

Must incorporate geometry in addition to colour

Goals:

Actual illumination

Actual surfaces

For computer graphics

Start simple, only make it more complex `when we need to', which means


Lambertian Surfaces

Model of body reflection

How much light hits the surface?

  1. Idealize light sources as points emitting light
    1. How much light does a source emit?
    2. How much light is there at a distance r from the source?
      • Segregate the light by direction
      • How much light per unit angle?
    3. How much light per square metre?
      • Falls off with distance.
      • How? Think how big the surface of a sphere is.
    4. How much of the surface does a square metre of the sphere cover?
      • Depends on the angle
      • How?
  2. What if the lights were (infinite) lines?
  3. What if the lights were (infinite) planes?
  4. What do we do in practice?

Comment. Two general aspects of the above are very important to getting things right in computer graphics

  1. The scaling arguments from dimensionality
  2. The geometric derivations of angular facts from small areas

How much light leaves the surface?

We are only interested in the light leaving the surface in a particular direction. Why?

What makes a Lambertian surface Lambertian?

What goes into the eye


Highlights

Part of the light didn't enter the body of the surface, but was reflected


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