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Harvard University. Adobe Systems. What do color changes reveal about an outdoor scene ?. *. *. IEEE Conference on Computer Vision and Pattern Recognition 2008. Outdoor time-lapse. =. £. Intrinsic Images. [ Weiss 2001, Matsushita et al. 2003,… ]. Time-lapse sequence.

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what do color changes reveal about an outdoor scene

Harvard University

Adobe Systems

What do color changes reveal about an outdoor scene?

*

*

IEEE Conference on Computer Vision and Pattern Recognition 2008

time lapse in computer vision

=

£

Intrinsic Images

[ Weiss 2001, Matsushita et al. 2003,… ]

Time-lapse sequence

Time-varying Shading

Texture

Editing

[ Sunkavalli et al. 2007 ]

Geo-location

[ Jacobs et al. 2007 ]

Time-lapse in Computer Vision
coherence in time lapse
Coherence in time-lapse
  • Most previous work makes use of only the temporal structure in time-lapse.
  • Outdoor time-lapse also has a colorimetric structure.

overcast sky

clear sky

sunset

outline
Outline
  • A physics-based model.
  • A method to fit the model to data.
  • Applications of the model.
outline1
Outline
  • A physics-based model.
  • A method to fit the model to data.
  • Applications of the model.
a model for outdoor time lapse
A model for outdoor time-lapse
  • Assumption 1 : Static scene
a model for outdoor time lapse1
A model for outdoor time-lapse
  • Assumption 2 : Linear Transforms for Re-illumination

observed pixel values

scene color under canonical lighting

color transform

¸

¸

¸

a model for outdoor time lapse2

sky illumination

sun illumination

mixing weights

A model for outdoor time-lapse
  • Assumption 3 : Ambient sky and direct sun illumination
a model for outdoor time lapse3
A model for outdoor time-lapse
  • Assumption 4 : 2-d subspace for daylight spectra

[ Judd et al. 1964, Sastri and Das 1968, …, Hernández-Andrés et al. 2000 ]

a model for outdoor time lapse4
A model for outdoor time-lapse
  • Assumption 4 : 2-d subspace for daylight spectra
a model for outdoor time lapse5
A model for outdoor time-lapse

illumination coefficients

a model for outdoor time lapse6
A model for outdoor time-lapse

scene color under canonical lighting (normalized)

a model for outdoor time lapse10
A model for outdoor time-lapse

1-d projection of normals onto solar plane

outline2
Outline
  • A physics-based model.
  • A method to fit the model to data.
  • Applications of the model.
fitting the model

illum.

bases

illum.

coeffs.

angular

velocity

albedo

shadows

brightness

normals

Fitting the model

over-constrained system

320 X 240 images, 100 frames

23,040,000 measurements

8,141,220 parameters

fitting the model1
Fitting the model

1. Estimate albedo and illumination bases

2. Estimate shadows

3. Estimate remaining parameters

Reconstruct

fitting results
Fitting results

original

reconstruction

240 x 360 images, 120 frames, ~5 mins. interval, 7.36% RMS error

fitting results1
Fitting results

original

error x 3

240 x 360 images, 120 frames, ~5 mins. interval, 7.36% RMS error

outline3
Outline
  • A physics-based model.
  • A method to fit the model to data.
  • Applications of the model.
application i color constancy
Application I : Color Constancy

[ D’Zmura and Lennie 1986, Forsyth 1990, Funt et al. 1991, Finlayson and Funt 1994, Brainard and Freeman 1997, Barnard et al. 1997, Finlayson et al. 2001, Ebner 2004,… ]

application i color constancy1
Application I : Color Constancy

original

color corrected

summary
Summary
  • Outdoor time-lapse sequences are ubiquitous.
  • They are a rich source of scene information.
  • By using both temporal and colorimetric coherence we can access that scene information.
future work
Future Work
  • Robust Fitting (mutual illumination, non-lambertian surfaces, foreground clutter).
  • Multiple viewpoints.
  • Estimating weather and atmospheric conditions.