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Distributed Ray Tracing Part 2PowerPoint Presentation

Distributed Ray Tracing Part 2

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Presentation Transcript

Overview

- Render Equation
- BRDF
- Importance Sampling
- Implementation

Integration over hemisphere

y0

ω0

y1

normal

ω1

eye

yi

ωi

x

Spherical sample direction

L(x,wo) = (2 PI / #samples) * ∑ [BRDF(x,wo,wi)*L(yi,-wi) * cos(n,ωi)]

Spherical Uniform Sampling

Generate two uniform random variables in [0,1) : ξx, ξy

x = sin(θ) cos(φ)

y = sin(θ) sin(φ)

z = cos(θ)

φ

Implement of Importance Sampling

- Generate enough samples (uniform samples)
- Compute the importance of each sample
- Build the CDF of importance
- Generate uniform random variables over [0,1)
- Use Inverse CDF to choose a sample
- Divide the contribution of each sample by its probability

Direct Lighting

- Use Phong Lighting Model.
- Add the lighting effect if visibility is one.

I * (Kd * dot(N, L) + Ks * pow(dot(E, R), Ns) )

N

E

L

R

Indirect Lighting

- Use importance sampling to choose direction
- If the direction hits a point yi ,compute the yi direct lighting

y0

ω0

y1

normal

ω1

eye

yi

ωi

x

L(x, ωo) = (2 PI / #samples) * ∑ [BRDF(x, ωo, ωi)*L(yi,-ωi) * cos(n,ωi)]

L(x, ωo) = (1.0 / #samples) * ∑ { L(yi ,-ωi) * [Kd * dot(ωi, N) + Ks * pow(dot(E, reflect(ωi, N)), Ns) ] }

N

E

yi

ωi

x

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