Transcript iCheat: A Representation for Artistic Control of Cinematic

iCheat: A Representation for
Artistic Control of Cinematic
Lighting
Juraj Obert
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Jaroslav Křivánek 2
Daniel Sýkora 2
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Sumanta Pattanaik 1
University of Central Florida
Czech Technical University in Prague
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Fabio Pellacini
Dartmouth College
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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
Scale/offset
matrix
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Final rendering
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Lighting Design Interface
•
Lighting design
interface
[Obert07]
1. 4D selection
a. caster
b. receiver
2. Modification
– hue / sat / intensity
– falloff …
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Lighting Design Pipeline
Real-time preview
Lighting design
interface
Scale/offset
matrix
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Final rendering
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Real-Time Preview
Direct-to-Indirect Transfer [Hasan06]
– Transfer matrix T
– direct on gather samples ->
Real-time preview
indirect on view samples
– Performance / flexibility modifications
– Row-wise matrix multiply
– Screen space sub-sampling and interpolation
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Lighting Design Pipeline
Real-time preview
Lighting design
interface
Scale/offset
matrix
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Final rendering
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Encoding of Indirect Illumination
Adjustments
Key idea:
– Discrete sampling in 4D
– Scale/offset modify the transport matrix T
T ' (v, g ) = s (v, g )T (v, g ) + o(v, g )
Scale/offset
matrix
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Example Edits:
Indirect Brightness
Sphere reflects more light into the environment
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Example edits:
Color 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
Scale/offset
matrix
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Final rendering
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Final rendering
Applicable to any GI algorithm
Our implementation:
– irradiance caching [Ward88]
– radiance caching [Křivánek05]
Radiance of gather rays
modified by the s / o matrices
– 4D interpolation
Final rendering
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Final Rendering Example
Original
Design 1
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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
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movie cars. In Proc. of IEEE Symposium on Interactive Ray Tracing (2006),
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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
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References
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J.: Lpics: A hybrid hardware-accelerated relighting engine for computer
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470.
RAGAN-KELLEY J., KILPATRICK C., SMITH B. W., EPPS D., GREEN P.,
HERY C., DURAND F.: The lightspeed automatic interactive lighting
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WARD G. J., RUBINSTEIN F. M., CLEAR R. D.: A ray tracing solution for
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