iCheat: A Representation for Artistic Control of Cinematic Lighting

1
iCheat A Representation for Artistic Control of
Cinematic Lighting
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1
2
Juraj Obert
Jaroslav Krivánek
Fabio Pellacini
1
2
Daniel Sýkora
Sumanta Pattanaik
1
University of Central Florida
2
Czech Technical University in Prague
3
Dartmouth College
2
Motivation

• Lighting crucial for film
• Story telling, scene mood, emotions
• Simple control more important than physical
  accuracy
• Direct illumination easy to control
• Indirect illumination hard to control

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Goal

• Simple artistic control of indirect illumination

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Existing Approaches

• Relighting engines
• Pellacini05, Ragan-Kelley07, Hasan06
• Goal-based lighting design
• Schoeneman93, Kawai93, Pellacini07
• Procedural modifications of shader code
  Christensen06
• Platform-specific solutions
• Tabellion04 filter lights

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Our Approach

• Holistic approach
• Direct control of the interaction between
• direct lighting
• materials
• geometry

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Lighting Design Pipeline
Real-time preview
Lighting design interface
Final rendering
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Lighting Design Interface

• Obert07
• 4D selection
• caster
• receiver
• Modification
• hue / sat / intensity
• falloff

Lighting design interface
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Lighting Design Pipeline
Real-time preview
Lighting design interface
Final rendering
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Real-Time Preview

• Direct-to-Indirect Transfer Hasan06
• Transfer matrix T
• direct on gather samples -gt indirect on view
  samples
• Performance / flexibility modifications
• Row-wise matrix multiply
• Screen space sub-sampling and interpolation

Real-time preview
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Lighting Design Pipeline
Real-time preview
Lighting design interface
Final rendering
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Encoding of Indirect Illumination Adjustments

• Key idea
• Discrete sampling in 4D
• Scale/offset modify the transport matrix T

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Example Edits Indirect Brightness
Sphere reflects more light into the environment
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Example editsColor bleeding
Blue wall bleeds more color on the cone
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Geometry Term Edits

• Modify the geometry term G(g,v)
• Linear w.r.t. direct illumination at gather
  samples
• Example effects
• Distance falloff modification, orientation-based
  modification, etc.

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General Edits

• Non-linear w.r.t. direct illumination at gather
  samples
• s / o matrices valid for current direct
  illumination
• Example effects
• 4D gamma correction, 4D HSV correction, etc.

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Lighting Design Pipeline
Real-time preview
Lighting design interface
Final rendering
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Final rendering

• Applicable to any GI algorithm
• Our implementation
• irradiance caching Ward88
• radiance caching Krivánek05
• Radiance of gather rays modified by the s / o
  matrices
• 4D interpolation

Final rendering
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Obert et al. iCheat A Representation for
Artistic Control of Cinematic Lighting
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Final Rendering Example
Original
Design 1
Design 2
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Animation

• Edits designed per key-frame
• Interpolated for other frames
• Possible artifacts when previously occluded large
  areas become suddenly visible

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Interpolation Example
Original
Original
Original
iCheat Keyframe
Interpolated frame
iCheat keyframe
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More Interpolation
Original
Original
Original
iCheat Keyframe
Interpolated frame
iCheat keyframe
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Video
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Conclusion

• Artistic control of indirect illumination
• Simple representation of edits
• Scale / offset factors for discretely sampled 4D
  transfer operator
• Comprehensive, renderer-independent, efficient
• Limitations
• More bulky than shader edits
• Possible artifacts due to discrete sampling

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Acknowledgements

• Vlasta Havran
• Golem ray tracer
• Universal Production Partners (upp.cz)
• Orion scene
• Ministry of Education of Czech Republic
• Center for Computer Graphics
• National Science Foundation
• CNS-070820, CCF-0746117

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References

• CHRISTENSEN P., FONG J., LAUR D., BATALI D. Ray
  tracing for the movie cars. In Proc. of IEEE
  Symposium on Interactive Ray Tracing (2006), pp.
  16.
• HAAN M., PELLACINI F., BALA K.
  Direct-to-indirect transfer for cinematic
  relighting. ACM Trans. Graph. (Proc. SIGGRAPH)
  25, 3 (2006), 10891097.
• KRIVÁNEK 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
  SIGGRAPH93 Proceedings (1993), pp. 147154.
• OBERT J., KRIVÁNEK J., SÝKORA D., PATTANAIK S.
  Interactive light transport editing for flexible
  global illumination. ACM SIGGRAPH 2007 sketches

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References

• PELLACINI F., BATTAGLIA F., MORLEY R. K.,
  FINKELSTEIN A. Lighting with paint. ACM Trans.
  Graph. (Proc. SIGGRAPH) 26, 2 (2007).
• PELLACINI F., VIDIMCE 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), 464470.
• 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), 469476.
• WARD G. J., RUBINSTEIN F. M., CLEAR R. D. A ray
  tracing solution for diffuse interreflection. In
  SIGGRAPH88 Proceedings (1988), pp. 8592.