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Recovering High Dynamic Range Radiance Maps from Photographs

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Recovering High Dynamic Range Radiance Maps from Photographs. Paul E. Debevec, Jitendra Malik. ... Differently Exposed Photographs. Image-Based Modeling & Rendering ... – PowerPoint PPT presentation

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Title: Recovering High Dynamic Range Radiance Maps from Photographs


1
Recovering High Dynamic Range Radiance Maps from
Photographs
  • Paul E. Debevec, Jitendra Malik. In SIGGRAPH 97,
    August 1997

2
Introduction
  • Dynamic Range of a scene is the contrast ratio
    (brightest / darkest parts)
  • Recovering High Dynamic Range Radiance Maps
  • Multiple Photographs
  • Recover Response function ( film response in
    exposure )
  • Differently Exposed Photographs
  • Image-Based Modeling Rendering
  • Image same ( exposure setting , film response
    function )
  • Recovering reflection models ( BRDF )
  • require absolute Radiance Values

3
Image Acquisition Pipeline
4
Film Response Recovery
  • The response of a film
  • Optical Density of film against the Exposure
  • digital number Z ( development , scanning ,
    digitization process )
  • Input Z ,

5
Film Response Recovery
  • To complete description
  • - ( unit exposure)
  • - weighting function
  • - pixel location ( Zmin Zmax , image )

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7
Constructing the HDR Radiance Maps
  • Curve - Radiance values ( associated with g )

Combining the multiple exposures - reduce Noise,
artifacts ( such as film grain )
8
Constructing the HDR Radiance Map
  • Storage
  • Map ? image format

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12
Rendering Synthetic Objects into Real Scene
Bridging Traditional and Image-Based Graphics
with Global Illumination and High Dynamic Range
Photography
  • Paul E. Debevec,. In SIGGRAPH 98, July 1998

13
Introduction
  • Scene Radiance Global Illumination
  • High Dynamic Range Image-based model
  • Illuminate the NEW objects
  • 3 components
  • Distant Scene
  • Local Scene
  • Synthetic Objects

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15
Introduction
  • Light Probe
  • HDR Panoramic Radiance Map ( near rendered
    location )
  • Light-Based Model

16
Illuminating Synthetic Objects with Real Light
  • Accurately Recording Light in a scene
  • Large areas of Indirect Light
  • Concentrated areas of Direct Light
  • Recovering HDR
  • Measure of Scene Radiance

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19
The General Method
  • Distant Scene ( a Light-Based Model )
  • Light-Based Model
  • Accurate measure of Incident Illumination
  • ( in vicinity of objects, desired viewpoint )
  • Local Scene ( approximate Material-Based Model )
  • Interact with the Synthetic Objects
  • Geometry, Reflectance characteristic
  • Synthetic Object
  • variety of Shapes , Materials

20
Compositing using a Light Probe
  • Constructing a Light-Based Model of real scene
  • Fully Dynamic Range Omnidirectional Radiance Map
  • Radiance measurement ? mapped ( geometry of
    Distant Scene )
  • Mapping from the Probe to the scene model
  • Mapping coordinates ( ball , world )
  • Position, Size, camera Parameter ( location in
    scene, focal length )
  • Assume Small , Orthograph ? good approximation
  • Creating Rendering

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