Realtime Rendering of Physically Based Optical Effects in Theory and Practice Masanori KAKIMOTO Tokyo University of Technology Table of Contents Introduction Basic geometrical optics Brief overview of ID: 480747
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Optics
Real-time
Rendering of Physically Based Optical Effects in Theory and Practice
Masanori KAKIMOTOTokyo University of Technology
Slide3
Table of Contents
Introduction
Basic geometrical
opticsBrief overview of wave opticsConclusionSlide4
Introduction
Real-time Rendering of Physically Based Optical Effects in Theory and
Practice
OpticsSlide5
Physics on Lights
Optics
Geometrical optics – a simple, practical model
Wave optics – more physically correct and complicatedElectromagnetism – a classical physics modelQuantum optics – a modern physics modelSlide6
Optics and Computer Graphics Theories
Computer graphics theories are based on optics
Vast majority of the theories and techniques upon geometrical optics
~1% taking wave optics into accountPhoton mapping borrows a concept ‘photon’ from quantum optics and use it in a geometrical optics frameworkSlide7
Topics
This course
Most topics are related with geometrical optics
Some are wave optics relatedThis talk covers:Basic g.o. knowledge for the rest of the courseBrief introduction of wave-related topics for a later talkSlide8
Basic Geometrical optics
Real-time Rendering of Physically Based Optical Effects in Theory and
Practice
OpticsSlide9
Geometrical Optics Models for CG
Pinhole camera model
Thin lens approximation
Thick lens approximationFull lens systemSlide10
Geometrical Optics Models for CG
Pinhole camera model
Thin lens approximation
Thick lens approximationFull lens system+ thickness+ aperture+ approximated refraction+ accurate refraction+ multi-wavelengths
etc.Slide11
Geometrical Optics Models and Effects
Geometrical optics
Thin lens
/ Thick LensFull simulated lensPinhole
Perspective projectionMotion blur
Bokeh
(defocus)
Focus breathing
Complex
Bokeh
Chromatic aberration
Optical
vignetting
Lens ghosts
+ aperture
+
approximated refraction
+ accurate
refraction
+ multi wavelengths
Natural
vignettingSlide12
Geometrical Optics Models and Effects
Geometrical optics
Thin lens
/ Thick LensFull simulated lensPinhole
Bokeh (defocus)Focus breathing
Complex
Bokeh
Chromatic aberration
Optical
vignetting
Lens ghosts
+ aperture
+
approximated refraction
+ accurate
refraction
+ multi wavelengths
Natural
vignetting
Today’s topicsSlide13
Geometrical Optics Models and Implementations
Graphics HW
(fixed pipeline)
Ray tracingAccumulation bufferProgrammable shader techniquesWavefront tracingPost processing
Geometrical optics
Pinhole
+ aperture
+ accurate refraction
Full lens system
Thin lens
/ Thick Lens
Distribution Ray tracingSlide14
Geometrical Optics Models and Implementations
Today’s
topics (geometrical
optics)Programmable shader techniquesPost processingGeometrical optics
Pinhole
+ aperture
+ accurate refraction
Full lens system
Thin lens
/ Thick Lens
Wavefront
tracingSlide15
Thin Lens – Fundamentals to Understand Real-Time Special Effects
Real-time techniques are based on thin lens theory
Many optical effects accounted for by thin lens
Some effects derived from full lens system modelEach can be mimicked by real-time techniques(extended thin lens theory)Slide16
Thin Lens Model
optical axis
(principal axis)
focal point
focal length
principal plane
incident light ray
center of lens
(p
rincipal point)
effective aperture diameterSlide17
Thin Lens Approximation – Rule 1
Incident light rays parallel to the principal axis always go through the focal point
optical axis
(p
rincipal axis)
focal point
focal length
principal plane
incident light ray
center of lens
(p
rincipal point)Slide18
Thin Lens Approximation – Rule 2
Incident light rays that passed through the focal point go parallel to the axis after exiting the lens
focal point
focal length
incident light raySlide19
Thin Lens Approximation – Rule 3
Incident light rays through the center of the lens
travel straight (never get refracted)
optical axis
incident light rays
center of lensSlide20
Rays Converge on a Certain Plane
Rays from an o
bject at distance converge on a plane at distance forming an image
object
image
film or sensor
focus distanceSlide21
Thin Lens Equation
object
image
filmSlide22
Thin Lens and Closer Objects
If the object gets closer, the converging plane (film) needs be farther from the lens
object
image
filmSlide23
Thin Lens and Far Objects
If the object is far, the film needs be closer to focal length
image
filmSlide24
Film Size and FOV for Infinite Focus
film
: Field of view
for infinite focusSlide25
Film Size and FOV for Closer Focus
film
: Field of view
for closer focusSlide26
F-number Represents Lens Brightness
film
: diameter of the lens
Smaller f-number means brighter imageSlide27
Effective F-number
film
Smaller f-number means brighter imageSlide28
Wave optics overview
Real-time Rendering of Physically Based Optical Effects in Theory and
Practice
OpticsSlide29
Rays travel straight
Introduction
Geometrical optics – virtually correct, simple
Wave optics – more physically correct, complicated
Geometrical optics
Wave optics
Waves propagate
concentrically
Slide30
Wave-Related Phenomena and Effects
Diffraction
Glare
Airy discInterferenceSurface coatingThin film color effectsPolarizationComplex reflectionImage dehazingCan be simulated with extended ray theories[CookTorrance1981], [Gondek1994], [Wolff1999], [Schechner 2001]Requires wave opticsCannot simulate with extended raysWave optics topics in this course focus on diffractionSlide31
Diffraction – A Major Cause of Glare
Geometrical optics
Wave optics
Diffraction
DiffractionSlide32
Diffraction Details
Later in this course
Wave optics based glare generation techniquesSlide33
Conclusion
Real-time Rendering of Physically Based Optical Effects in Theory and
Practice
OpticsSlide34
Conclusions
Most computer graphics theories rely on geometrical optics
Real-time techniques basically use thin lens approximation
Effects beyond thin lens can be mimicked (later in this course, e.g., aberrations)Popular wave optics effects are based on diffraction