7.Image Processing (Rendering 1)

Question 1

What’s the difference between local and global illumination model?

Answer 1

NO INTERACTION between objects

Question 2

Example of approximation?

Answer 2

The interaction of light and matter

Question 3

What is diffusely reflected light?

Answer 3

Light that has been absorbed by atoms and remitted

Question 4

In which directions is light diffusely reflected, what is the visual result of this?

Answer 4

All directions, it looks matte

Question 5

What is specularly reflected light?

Answer 5

light that is bouncing off top of surface

Question 6

What is the effect of specularly reflected light on objects visually?

Answer 6

pretty pretty shiny shiny

Question 7

What is the cause of imperfect specular reflection?

Answer 7

bumpy specular surface, light ray is reflected across small range of angles

Question 8

Are most objects specular or diffuse reflectors?

Answer 8

TRICK question.. they are a mix of both

Question 9

What is ka?

Answer 9

The ambient reflection coefficient of the surface

Question 10

Why do we use ka?

Answer 10

Iambient = kaIa (amount of ambient light diffusely reflected by surface)

Question 11

V1 of local illumination model?

Answer 11

I = kaIa

Question 12

What is the effect of applying just ambient illumination?

Answer 12

• uniform illumination

- lose 3D information

Question 13

How do we describe the diffuse reflectivity of a surface?

Answer 13

kd value

Question 14

V2 of local illumination model? (I = ambient + diffuse)

Answer 14

I = kala + Ipkd(N*L)
L: direction of light source
N: surface normal
Ip: Intensity at point
N*L = cos9

Question 15

What is the variation of the inverse square law that we use? (Ie = Ip/tpid^2)

Answer 15

Ie = Ip / (Kc+Kld+Kqd^2)

Question 16

Why do we not use the inverse square law?

Answer 16

d^2 changes too rapidly

Question 17

V3 of local illumination model? (I = ambient + distance[diffuse])

Answer 17

I = kaIa + (IpKdN*L)/d’

where d’ = (Kc+Kld+Kqd^2)