8.Image Processing (Rendering 2)

Question 1

What does specular reflection vary with?

Answer 1

• angle (Reflection, View)

- incident angle & wavelength λ

Question 2

Effect of changing angle (Reflection, View) on reflected light?

Answer 2

Increase angle = decrease observed reflection

Question 3

Phong specular function to relate reflected light / angle(Reflection, View)?

Answer 3

cos^n(φ)

Question 4

Which equation relates reflected light/λ/incidence angle?

Answer 4

Fresnel

Question 5

Are a incident angle or wavelength used in practice in graphics?

Answer 5

No, specular coefficient ks is used

Question 6

V4 of the local illumination model? (I = ambient+ distance(diffuse+specular))

Answer 6

I = kala + (Ip/d’)[kd(NL)+ks(R*V)^n]

Question 7

How do we express light colour?

Answer 7

RGB intensities (Ipr,Ipg,Ipb)

Question 8

How do we express surface colour (split coefficients)?

Answer 8

kar,kaG,kaB

kdR,kdG,ldB

Question 9

V5 of the local illumination model (incorporates colours)

Answer 9

Ir = ambientR + distance(diffuseR+specular)

Question 10

What are the three shading methods?

Answer 10

Flat, Gouraud and Phong (FGP)

Question 11

Alternative names for the shading methods?

Answer 11

Constant, Intensity and Normal-vector

Question 12

How is flat shading produced?

Answer 12

calculate colour of one vertex

apply to all triangle

Question 13

What does the bad mach banding effect in flat shading mean?

Answer 13

Our eyes are very good at detecting edges

Question 14

How is Gouraud shading computed?

Answer 14

INTERPOLATION of colours, smooth out discontinuities between polygons

Question 15

Name two problems of gouraud shading?

Answer 15

• Specular highlights may be lost

- Mach banding may still be visible

Question 16

How is Phong shading computed?

Answer 16

apply illumination model to every pixel

Question 17

Does Phong maintain specular highlights?

Answer 17

yas