depth-of-field rendering by pyramidal image processing martin kraus (tu münchen) and magnus...
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Depth-of-Field Renderingby Pyramidal Image Processing
Martin Kraus (TU München) and
Magnus Strengert (Universität Stuttgart)
E U R O G R A P H I C S07
01 Introduction
02 Related work
03 Proposed method
04 Experiments
05 Future work
Outline of this Talk00
What Is Depth of Field?• The depth in front and beyond the focus
plane where objects appear to be in focus
• A property of all real optical systems– only virtual pin-hole cameras have infinite
depth of field
• Used for important photographic and cinematographic techniques
I N T R O D U C T I O N01
photo by Jon Sullivan (http://pdphoto.org/PictureDetail.php?mat=pdef&pg=8202)
photo by "che" (http://commons.wikimedia.org/wiki/Image:Dandelion_clock_detail.jpg)
Classification of Techniques:• Splatting [Potmesil & Chakravarty 1982]
• Stochastic sampling [Cook et al. 1984] – e.g., in distributed ray tracing or in REYES– state of the art in offline rendering
• Pre-filtering [Rokita 1993]– lots of artifacts [Demers 2004]– state of the art in real-time rendering
• Blurring of sub-images [Barsky 2004]
R E L A T E D W O R K02
High Quality in Real Time?• Real-time performance requires:
– independence of scene complexity• excludes stochastic sampling
– thus: image post-processing of a pin-hole color image and depth map
• independence of image synthesis for free
– convolution filtering is too expensive• even with FFTs on GPUs
– thus: blurring using pyramid algorithms
R E L A T E D W O R K02
High Quality in Real Time?• High image quality requires:
– smooth blurring without interpolation artifacts• pyramid blurring [Kraus & Strengert 2007]
– no incorrect color bleeding• excludes pre-filtering• separate blurring of sub-images
– disocclusion of semi-transparent pixels• inpainting of colors and depths with pyramid
algorithm [Strengert et al. 2006]
R E L A T E D W O R K02
Overview
P R O P O S E D M E T H O D03decomposition into sub-images
blending of sub-images blurring
resulting image
pin-hole image & depth map
1
2
5
3
4
matting disocclusion
Decomposition• decompose into sub-images and cull
foreground pixels according to depth map
P R O P O S E D M E T H O D03 1
Disocclusion• for each sub-image: disocclude culled
foreground (using pyramidal inpainting)
P R O P O S E D M E T H O D03 2
Matting• for each sub-image: compute alpha-
matting according to each pixel's depth
P R O P O S E D M E T H O D03 3
Blurring• for each sub-image: blur color and alpha
(using pyramidal blurring)
P R O P O S E D M E T H O D03 4
Blending• back-to-front blending of all sub-images
P R O P O S E D M E T H O D03 5
result computed in 70.4 ms
(12 sub-images, hardware:
NVIDIA GeForce 7900 GTX)
Main Features• independent of scene complexity
– and independent of image synthesis
• interactive perfomance on GPUs– real-time for small circles of confusion
• high image quality– avoids artifacts of pre-filtering techniques– let's do some experiments …
P R O P O S E D M E T H O D03
Our Method vs. pbrt• pbrt uses
stochasticsampling
• Which iswhich?
E X P E R I M E N T S04
Our Method vs. pbrt
E X P E R I M E N T S04pbrt
our method
Our Method vs. pbrt• Which is
which?
E X P E R I M E N T S04
Our Method vs. pbrt
E X P E R I M E N T S04pbrt
our method
Can We Break Our Method?• Yes, with a
very largelens radius.
E X P E R I M E N T S04pbrt
our method too opaquebleeding gray
Can We Break Our Method?
E X P E R I M E N T S04• Video with very large lens radii: eg07.mov
– also available at: http://wwwcg.in.tum.de/Research/Publications/DepthOfField
Are We there yet?• No, but we avoid typical rendering artifacts
of real-time techniques
• Specialized variants for better performance and image quality
• Alternative blur filters
• High-potential application:– gaze-directed focus
F U T U R E W O R K05
• The photos appear courtesy of "che" and
Jon Sullivan.
• The dragon model appears courtesy of the Stanford University Scanning Repository.
• The pbrt scene appears courtesy of Gregory Humphreys and Matt Pharr.
A C K N O W L E D G M E N T S06
Thank you!
And have a safe trip home!
Questions?
E U R O G R A P H I C S07
E U R O G R A P H I C S07