Wave optics based - PowerPoint Presentation

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Wave optics based

glare generation techniques

Real-time

Rendering of Physically Based Optical Effects in Theory and PracticeMasanori KAKIMOTOTokyo University of Technology

Slide3

Wave optics based glare

generation techniques

Table of Contents

IntroductionRelated workFundamental theoryGlare pattern image generationImplementation and examplesConclusionSlide4

Introduction

Real-time Rendering of Physically Based Optical Effects in Theory and

Practice

Wave optics based glare generation techniquesSlide5

Introduction

Vast majority of

computer graphics theories are based

upon geometrical optics~1% taking wave optics into accountIf you need reality for glare effects,Then wave optics may helpComputation power today is advantageousSlide6

Wave-Related Phenomena and Effects

Diffraction

Glare

Airy discInterferenceSurface coatingThin film color effectsPolarizationComplex reflectionImage dehazingCan be simulated w/ extended ray theories[CookTorrance1981], [Gondek1994], [Wolff1999], [Schechner 2001]Requires wave opticsCannot simulate with extended rays

Wave optics topics in this course focus on diffractionSlide7

An Example of GlareSlide8

A Simple Experiment of Glare (1)

A pen-light used for

the

experimentA direct snapshot of the lightSlide9

A Simple Experiment of Glare (2)

False eyelashes attached

A direct snapshot

of the lightSlide10

A Simple Experiment of Glare (3)

Eyelashes rotated 90 degrees

A direct snapshot

of the lightSlide11

Related work

Real-time Rendering of Physically Based Optical Effects in Theory and

Practice

Wave optics based glare generation techniquesSlide12

Early Work for Glare Effect

Cross filter lens flare effect

[Shinya et al.1989]

Glare by eyelashes for night driving scene[Nakamae et al. 1990]Nakamae, E., K. Kaneda, T. Okamoto, and T. Nishita: A Lighting Model Aiming at Drive Simulators, in Proc. ACM SIGGRAPH ’90, pp. 395–404, 1990.Slide13

Early Work for Glare (cont’d)

Glare billboard

[

Rokita 1993]Eye structure analysis and glare filter compositor [Spencer et al. 1995]Glare filter on HDR images [Debevec et al. 1997]Slide14

Real-Time Techniques for Glare

Real-time environment lighting

[Mitchell 2002]

Racing game implementation [Kawase 2002, 2003]©2002 BUNKASHA PUBLISHING CO.,LTD.Slide15

Physically-Based Aproaches

Glare caused by Fraunhofer diffraction

[

Kakimoto et al. 2004, 2005]Inside-the-eye Fresnel diffraction[Ritschel et al. 2009]Real-time lens flare [Hullin et al. 2011]Slide16

Fundamental theory

Real-time Rendering of Physically Based Optical Effects in Theory and

Practice

Wave optics based glare generation techniquesSlide17

Diffraction – A Major Cause of Glare

Geometrical optics

Wave optics

Diffraction

DiffractionSlide18

Diffraction – A Major Cause of GlareSlide19

Huygens-Fresnel Principle Accounts for Diffraction

Waves propagate

concentrically,

at EVERYWHERE on the wave frontEnvelope curve of the secondary waves form the next wave frontSlide20

An Analysis of Diffraction

Aperture

Incident light

Wave front

Observation screenSlide21

A Model for Diffraction

Aperture

S

Observation region

Object

region

: Complex wave amplitude

at point

: wave length

 Slide22

See Appendix for the AnalysisSlide23

Fraunhofer Diffraction

: Wave intensity

: Amplitude of incident light

: Fourier transform operator

: Sufficiently large distance

for

aperture size and

 Slide24

Fraunhofer Approximation in a Lens System

The diffraction image through a lens system can be denoted using a 2D Fourier transform of the object that causes diffraction.

[Goodman 1968]

 Slide25

Glare pattern image generation

Real-time Rendering of Physically Based Optical Effects in Theory and

Practice

Wave optics based glare generation techniquesSlide26

Diffraction w.r.t. Wave Length

 Slide27

Glare Pattern Image and Wave Lengths

The 2D pattern scaling

Diffraction intensity

 Slide28

Glare by a Hexagonal Diaphragm

No filter

Hexagonal diaphragm

Output GlareSlide29

A Cross Filter Pattern

Cross filter pattern

Pupil diaphragm

Output

GlareSlide30

Eyelashes and Iris Diaphragm

Drawn pattern of an eyelid and eyelashes

Pupil diaphragm

Glare for Red, Green, and Blue wave lengthsSlide31

Dynamic Glare

How glare changes its shape while moving

Light source position

Choose an input obstacle image

Output glare image

 Slide32

Dynamic Glare

How glare changes its shape while moving

Light source position

Choose an input obstacle image

Output glare image

 Slide33

Dynamic Glare

How glare changes its shape while moving

Light source position

Choose an input obstacle image

Output glare image

 Slide34

Special Case: Circular Aperture

Use the analytical formula for ‘Airy Disc’ rather than FFT

View angle

Aperture radius

:

The Bessel function of the first kind

Output

Glare

(Airy Disc)

Input circular aperture

*

For

a rectangular

aperture,

you can use another formulaSlide35

An Implementation and examples

Real-time Rendering of Physically Based Optical Effects in Theory and

Practice

Wave optics based glare generation techniquesSlide36

Multi-Spectra Integration

Glare intensity

(

A 2D FFT result)

Spectral power distribution of the light source

Color matching function

Conversion from XYZ to RGB (3

3 matrix)

RGB Glare image for a light sourceSlide37

Light source intensity

Processing Flow

FFT

Fraunhofer diffraction

×

Light source spectra

Color matching

func

.

Single spectrum glare image

Glare image

Output glare image

Input images (eyelashes and a pupil)Slide38

Sampling and Accumulation along Wave Lengths

100 samples along visible light wave lengths (380nm – 700nm) may be sufficient

Output glare images

: One sample : 4 samples

 : 100 samples

 Slide39

Scale and Accumulate a Seed Glare Image

Need not compute FFT for each

Seed glare image assuming

Scale image by

Scale pixel value by

……

Accumulate

 Slide40

A Result and a Reference

×

Light source, attachment and a camera

A real snapshot

Output glare image of an infinite point light

Input object and pupil image

 Slide41

Results for Different Light Sources

A blue LED

An HID

*

headlamp

An

incandes

-cent

lamp

A white LED

The sun

*

High Intensity Discharge

 Slide42

Results for Different Brightness

Varied results from a single HDR glare image

Multiply the brightness of the current pixel in the input scene

Measured headlamp intensity distributionUnit: cd

L

=68496

L

=17332

L

=3188

L

=672

L

=53

The

L

is equivalent to

, a squared amplitude of the incident light

 Slide43

Rendering Glare from Light Sources Directly Viewed

Find the light source in screen space

Multiply the brightness according to the directional light distribution

Scatter or overlay glare imageGlare from directly viewed light sourcesSlide44

Rendering Glare on Highly Reflective Surfaces

Prepare a light map of bright light sources

Detect the reflecting points in

screen spaceMultiply the mapped texel brightnessScatter or overlay glare imageGlare on a reflective modelThe used light mapSlide45

An Application to Headlamp Evaluation

Incandescent lamps

HID

lamps

High beam

Low beam

Spectral power distributions

Directional intensity distributions

[Kakimoto et al. 2010]Slide46

Conclusions

Real-time Rendering of Physically Based Optical Effects in Theory and

Practice

Wave optics based glare generation techniquesSlide47

Conclusions

Glare

image

is a 2D Fourier Transform of the obstacle imageMake a seed glare image by FFTCompute an intermediate HDR glare image by resizing, amplifying, and accumulating the seed glare along Use spectral distributions of light source and sensitivityScatter or use billboard for each pixel detected as ‘bright’Multiply the intermediate glare by the pixel brightness Slide48

References

Goodman, J. W

. 1968.

Introduction to Fourier Optics. McGraw-Hill.Shinya, M., Saito, T., and Takahashi, T. 1989. Rendering Techniques for Transparent Objects. Proc. Graphics Interface ’89, pp. 173–182.Nakamae, E., Kaneda, K., Okamoto, T., and Nishita, T. 1995. A Lighting Model Aiming at Drive Simulators. Proc

. SIGGRAPH ’90, pp

. 395–404, 1990.

Rokita

,

P., 1993. A model for rendering high intensity

lights. Computers & Graphics, 17, 4, pp. 431–437.

Spencer

, G.,

Shirley

,

P., Zimmerman

,

K., and Greenberg, D. P. 1995. Physically-Based Glare Effects

for Digital

Images. Proc

.

SIGGRAPH

’95, pp.

325–334.

Stam

, J

. 1999. Diffraction

shaders

. Proc

.

SIGGRAPH

’99, pp.

101–110.

Mitchell, J. L. 2002.

RADEON 9700 Shading. State of the Art

in Hardware

Shading, Course Note #17, SIGGRAPH

2002.

Kawase

, M., and Nagaya, M. 2002. Real-time CG rendering techniques in DOUBLE-S.T.E.A.L. CEDEC 2002

,

Tokyo, No

.

1-3-A. (In Japanese)

Kawase

, M. 2003. Frame

Buffer

Postprocessing

Effects in DOUBLE-S.T.E.A.L (

Wreckless

). GDC 2003.Slide49

References

Kakimoto

, M., Matsuoka, K.,

Naemura, T., Nishita, T., and Harashima, H. 2004. Glare generation based on wave optics. Proc. Pacific Graphics 2004, pp. 133–142. (reprinted as CGF 24, 2, pp. 185–193)Kakimoto, M., Matsuoka, K., Naemura, T., Nishita, T., and Harashima, H. 2005. Glare Simulation and Its Application to Evaluation of Bright Lights with Spectral Power Distribution, Posters, SIGGRAPH 2005.Ritschel

, T., Ihrke, M., Frisvad

, J. R., Coppens, J.,

Myszkowski

, K., and Seidel, H.-P. 2009. Temporal Glare: Real-Time Dynamic Simulation of the Scattering in the Human Eye. Computer Graphics Forum (Proc.

Eurographics

).

Kakimoto, M.,

Nishita

, T.,

Naemura

, T.,

Harashima

, H. 2010. A Glare Effect Application to Headlamp Design Verification. Journal of IIEEJ (Institute of Image Electronics Engineers of Japan), 39, 4, 369–375. (In Japanese)

Hullin

, M., Eisemann, E., Seidel, H., Lee, S. 2011.

Physically-Based Real-Time Lens Flare Rendering. ACM

Trans. Graph.

30, 4, Article 108 (July 2011), 9 pages.

Cuypers

, T., Haber, T.,

Bekaert

, P., Oh, S. B., and

Raskar

, R. 2012. Reflectance model for diffraction. ACM Trans. Graph.

31

, 5, Article 122 (August 2012), 11 pages.