icheat: a representation for artistic control of cinematic lighting juraj obertjaroslav křivánek...

iCheat: A Representation for iCheat: A Representation for Artistic Control of Cinematic Artistic Control of Cinematic

LightingLighting

Juraj Obert Jaroslav Křivánek

Daniel Sýkora

Fabio Pellacini

Sumanta Pattanaik12

321

1University of Central Florida

Czech Technical University in Prague

Dartmouth College

2

3

Obert et al. Obert et al. iCheat: A Representation for Artistic Control of Cinematic iCheat: A Representation for Artistic Control of Cinematic

LightingLighting 22

MotivationMotivation

Lighting crucial for filmLighting crucial for film– Story telling, scene mood, emotionsStory telling, scene mood, emotions

Simple control more important than Simple control more important than physical accuracyphysical accuracy– Direct illumination: easy to controlDirect illumination: easy to control– Indirect illumination: hard to control Indirect illumination: hard to control


LightingLighting 33

GoalGoal

Simple artistic control of indirect Simple artistic control of indirect illuminationillumination


LightingLighting 44

Existing ApproachesExisting Approaches

Relighting enginesRelighting engines[Pellacini05, Ragan-Kelley07, Hasan06][Pellacini05, Ragan-Kelley07, Hasan06]

Goal-based lighting design Goal-based lighting design [Schoeneman93, Kawai93, Pellacini07][Schoeneman93, Kawai93, Pellacini07]

Procedural modifications of shader code Procedural modifications of shader code [Christensen06][Christensen06]

Platform-specific solutionsPlatform-specific solutions[Tabellion04] – filter lights[Tabellion04] – filter lights

Our ApproachOur Approach

““Holistic approach”Holistic approach”

Direct control of the interaction betweenDirect control of the interaction between– direct lightingdirect lighting– materialsmaterials– geometrygeometry


LightingLighting 55


LightingLighting 66

Lighting Design PipelineLighting Design Pipeline

Lighting design interface

Scale/offsetmatrix Final rendering

Real-time preview


LightingLighting 77


Lighting Design InterfaceLighting Design Interface

• [Obert07][Obert07]

1.1. 4D selection4D selectiona.a. castercaster

b.b. receiverreceiver

2.2. ModificationModification– hue / sat / intensityhue / sat / intensity– falloff …falloff …


LightingLighting 88




Real-time preview


LightingLighting 99

Real-Time PreviewReal-Time Preview

Real-time preview

Direct-to-Indirect Transfer [Hasan06]Direct-to-Indirect Transfer [Hasan06]– Transfer matrix TTransfer matrix T

– direct on gather samples -> direct on gather samples -> indirect on view samplesindirect on view samples

– Performance / flexibility modificationsPerformance / flexibility modifications– Row-wise matrix multiplyRow-wise matrix multiply– Screen space sub-sampling and interpolationScreen space sub-sampling and interpolation


LightingLighting 1010




Real-time preview



Encoding of Indirect Illumination Encoding of Indirect Illumination AdjustmentsAdjustments

Scale/offsetmatrix

Key idea: Key idea: – Discrete sampling in 4DDiscrete sampling in 4D– Scale/offset modify the transport matrix Scale/offset modify the transport matrix TT

),(),(),(),(' gvogvTgvsgvT



Example Edits: Example Edits: Indirect BrightnessIndirect Brightness

Sphere reflects more light into the environment



Example edits:Example edits:Color bleedingColor bleeding

Blue wall bleeds more color on the cone



Geometry Term EditsGeometry Term Edits

Modify the geometry term Modify the geometry term GG((gg,,vv))

LinearLinear w.r.t. direct illumination at gather w.r.t. direct illumination at gather samplessamples

Example effects:Example effects:– Distance falloff modification, orientation-based Distance falloff modification, orientation-based

modification, etc.modification, etc.



General EditsGeneral Edits

Non-linearNon-linear w.r.t. direct illumination at gather w.r.t. direct illumination at gather samplessamples– s / o matrices valid for current direct illuminations / o matrices valid for current direct illumination

Example effectsExample effects– 4D gamma correction, 4D HSV correction, etc.4D gamma correction, 4D HSV correction, etc.






Real-time preview



Final renderingFinal rendering

Final rendering

Applicable to any GI algorithmApplicable to any GI algorithm

Our implementation: Our implementation: – irradiance caching [Ward88] irradiance caching [Ward88]

– radiance caching [Kradiance caching [Křivánek05řivánek05]]

Radiance of gather rays Radiance of gather rays modified by the s / o matricesmodified by the s / o matrices– 4D interpolation4D interpolation



Final Rendering ExampleFinal Rendering Example

Original Design 1 Design 2



AnimationAnimation

Edits designed per key-frameEdits designed per key-frame

Interpolated for other framesInterpolated for other frames– Possible artifacts when previously occluded Possible artifacts when previously occluded

large areas become suddenly visiblelarge areas become suddenly visible



Interpolation ExampleInterpolation Example

iCheat keyframe iCheat KeyframeInterpolated frame

Original Original Original



More InterpolationMore Interpolation

iCheat keyframe iCheat KeyframeInterpolated frame

Original Original Original



VideoVideo



ConclusionConclusion

Artistic control of indirect illuminationArtistic control of indirect illumination

Simple representation of editsSimple representation of edits– Scale / offset factors for discretely sampled Scale / offset factors for discretely sampled

4D transfer operator4D transfer operator– Comprehensive, renderer-independent, Comprehensive, renderer-independent,

efficientefficient

LimitationsLimitations– More bulky than shader editsMore bulky than shader edits– Possible artifacts due to discrete samplingPossible artifacts due to discrete sampling



AcknowledgementsAcknowledgements

Vlasta Havran Vlasta Havran – Golem ray tracerGolem ray tracer

Universal Production Partners (upp.cz)Universal Production Partners (upp.cz)– Orion sceneOrion scene

Ministry of Education of Czech RepublicMinistry of Education of Czech Republic– ““Center for Computer Graphics”Center for Computer Graphics”

National Science FoundationNational Science Foundation– CNS-070820, CCF-0746117CNS-070820, CCF-0746117



ReferencesReferencesCHRISTENSEN P., FONG J., LAUR D., BATALI D.: Ray tracing for the movie cars. In Proc. of IEEE Symposium on Interactive Ray Tracing (2006), pp. 1–6.

HAŠAN M., PELLACINI F., BALA K.: Direct-to-indirect transfer for cinematic relighting. ACM Trans. Graph. (Proc. SIGGRAPH) 25, 3 (2006), 1089–1097.

KŘIVÁNEK J., GAUTRON P., PATTANAIK S., BOUATOUCH K.: Radiance caching for efficient global illumination computation. IEEE Transactions on Visualization and Computer Graphics 11, 5 (September/October 2005).

KAWAI J. K., PAINTER J. S., COHEN M. F.: Radioptimization: Goal based rendering. In SIGGRAPH’93 Proceedings (1993), pp. 147–154.

OBERT J., KŘIVÁNEK J., SÝKORA D., PATTANAIK S.: Interactive light transport editing for flexible global illumination. ACM SIGGRAPH 2007 sketches



ReferencesReferencesPELLACINI F., BATTAGLIA F., MORLEY R. K., FINKELSTEIN A.: Lighting with paint. ACM Trans. Graph. (Proc. SIGGRAPH) 26, 2 (2007).

PELLACINI F., VIDIMČE K., LEFOHN A., MOHR A., LEONE M., WARREN J.: Lpics: A hybrid hardware-accelerated relighting engine for computer cinematography. ACM Trans. Graph. (Proc. SIGGRAPH) 24, 3 (2005), 464–470.

RAGAN-KELLEY J., KILPATRICK C., SMITH B. W., EPPS D., GREEN P., HERY C., DURAND F.: The lightspeed automatic interactive lighting preview system. ACM Trans. Graph. (Proc. SIGGRAPH) 26, 3 (2007).

TABELLION E., LAMORLETTE A.: An approximate global illumination system for computer generated films. ACM Trans. Graph. (Proc. SIGGRAPH) 23, 3 (2004), 469–476.

WARD G. J., RUBINSTEIN F. M., CLEAR R. D.: A ray tracing solution for diffuse interreflection. In SIGGRAPH’88 Proceedings (1988), pp. 85–92.

icheat: a representation for artistic control of cinematic lighting juraj obertjaroslav křivánek...

Documents

motivation lighting

interpolation slide

environment slide

cone slide

gvogvtgvsgvt slide

emotions simple control

intensity falloff slide

samples indirect