Michael Langer Heinrich Blthoff

1
Shape from Shading under diffuse lighting does
dark mean deep?

• Michael Langer
  Heinrich Bülthoff
• NEC Research Institute
  MPI for Biological
  Cybernetics
• Princeton, NJ
  Tübingen,
  Germany

Presentation at the European Conference on
Visual Perception, Oxford, U.K, August 1998
2
SFS on a Sunny Day
?
L
?
N(x)
?
?
I(x) N(x) L
3
SFS on a Sunny Day
?
?
I(x) N(x) L
4
SFS on a Cloudy Day
?
(x)
5
SFS under Diffuse Lighting
?
?
?
?
?
I(x)
N(x)
L d L
?
(x)
?
?(x) angle of visible light source
6
SFS under Diffuse Lighting
7
Hill or Valley ?
8
SFS under Diffuse Lighting
Does Dark Means Deep?
9
Does Dark Means Deep?
local intensity maximum
10
Height-Intensity Correlation
11
Correlated Condition
12
Anti-Correlated Condition
13
1. Grey Silhouette
14
2. Pair of Probes
15
3. Test Which is higher ?
16
Which is higher ?
N17
percent correct
_

Correlation
17
Which is brighter ?
18
Which is brighter ?
height
N10
brightness
percent correct
_

Correlation
19
Computational Modeling
I(x) ? (x)

(Langer and Zucker 93)
?
?
?
?
I(x) N(x) L d L
?
?(x)
(Stewart and Langer 96)
20
Human - Models
1
0.8
0.6
percent correct
0.4
0.2
0
human LZ 93 SL 96
21
Conclusion

• Dark-means-deep cannot account for
  shape-from-shading perception under diffuse
  lighting.
• Point source models are insufficient.
• Our visual system uses a more accurate physical
  model which is based on the angle of the visible
  light source.