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# Local Illumination Pictures PowerPoint PPT Presentation

Local Illumination Pictures. Lighting interaction between objects’ materials and geometry, and the light sources Shading the process of performing the lighting computations and determining pixels’ color from them. Three basic models discussed Flat Gouraud Phong. Programming OpenGL

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Local Illumination Pictures

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### Local Illumination Pictures

Gerda Kamberova

Lightinginteraction between objects’ materials and geometry, and the light sources

Shadingthe process of performing the lighting computations and determining pixels’ color from them. Three basic models discussed

Flat

Gouraud

Phong

Programming

OpenGL

Updating the hierarchical scene model

Gerda Kamberova

### Lambert’s law

Ip(L.N)

Ip

N

L

P

It does not matter where the viewer is, he sees reflected light in the

mount of Ip(L.N)

Gerda Kamberova

### Specular reflection

N

L

R

Ip

V

P

Light reflected in direction of V = Ip(R.V)

Each time viewer changes position must be recomputed 

Gerda Kamberova

### Specular reflection

N

L

R

Ip

a

a

-b

b

P

R = -b+a = -(L-a)+a = -(L-(L.N)N)+(L.N)N = 2(L.N)N – L

If the relative position of light and object changes,

must be recomputed

Gerda Kamberova

### Using the half-way vector to speed up computation

N

H

L

R

Ip

V

P

H=(L+V)/|L+V|

2(H.N) approximates (R.V),

H is easier to compute than R

Gerda Kamberova