Illumination

Question 1

What is a Local Illumination Model?

Answer 1

This is where the light comes from a single source

and objects are NOT illuminated from reflected light

Question 2

What is a Global Illumination Model?

Answer 2

This is where the light comes from a multiple sources

and objects are illuminated from reflected light from other objects

Question 3

What is a Diffuse Reflection?

Answer 3

This is where the light is reflected uniformly across the hemisphere

The surface looks fairly dull

Question 4

What is a Perfect Specular Reflection?

Answer 4

This is where the angle of incidence is equal to the angle of reflection

Question 5

What is an Imperfect Specular Reflection?

Answer 5

This is where most of the light is reflected at the angle of reflection,

but some light is reflected at angles around this

Question 6

What does the ambient illumination coefficient for an object do?

Answer 6

This decides how much ambient light is reflected from the object

Question 7

What is the Diffuse Reflection Coefficient?

Answer 7

This decides how much light is diffusely reflected from an object

Question 8

How do we approximate the amount of observed specular light, if the viewing angle is V, and the light intensity is I.

Answer 8

Observed Specular Light

=

I * cos(V) ^ N

If N is large, we have a specular reflection over a smaller area

Question 9

What does Fresnel’s Equation describe?

Answer 9

Given the angle of Incidence, and the angle of Transmission

It tells us what fraction of the Incident Light gets reflected

Phi is the angle of Incidence

Theta is the angle of Transmission

We approximate this with a constant

Question 10

Describe loosely the Illumination Equation

Answer 10

I

ambient light +

light_intensity/distance *

( diffuse + specular )