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Writer's pictureLingheng Tao

CG Tech Interview #2 Physically Based Rendering

This section serves as a summary of all the Physically-Based Rendering concepts.


Radiometry


Physics


  • Photon Energy: energy that moves along a ray, assuming no wave properties. It has position e, direction d, and wave length λ.

  • Radiant Energy: the total energy radiated by all the rays from any λ.

  • Spectral Energy: the total energy at a specific λ.

  • Flux: radiant energy a second.

  • Irradiance: arrival flux at unit area (per square meter).

  • Radiant Exitance: exitted flux at unit area.

  • Radiance: irradiance per solid angle.


Integrators


  • Solid Angle

  • Irradiance by Integral Over Spheric Surface

  • Irradiance by Integral Over Area

Properties

  • Lambert's Law

  • Radiance's Invariant Property Along A Ray

Probability


Monte Carlo Integration


  • To Be Integrated:

  • Estimator

p(x) is the sampling distribution function.


Sampling


Rejection Sampling


  • Random On Disk

  • Random In Unit Sphere

  • Random On Unit Sphere

  • Random On Unit Hemisphere By XY plane

  • Random On Unit Hemisphere By Any Plane


Importance Sampling


  • Direct Light

  • Ambient Light

  • MIS

  • Balance Heuristic

  • Power Heuristic


BSDF


BRDF

  • Phong

  • Blinn-Phong

, where


  • Diffuse

  • Torrance-Sparrow

, where

, and in Beckmann Distribution Model,

  • Oren-Nayar

, where



Stochastic Path Tracing


Algorithm

  • Russian Roulette

Next Event Estimation


Multiple Importance Sampling


Photon Mapping


Bidirectional Path Tracing


Volumetric Rendering


Procedures


  • Absorption

  • Emission

  • Outscattering

  • Inscattering


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