Michael Langer Heinrich Bülthoff NEC Research Institute MPI for Biological Cybernetics Princeton, NJ Tübingen, Germany Shape from Shading under diffuse lighting: does dark mean deep? Presentation at the European Conference on Visual Perception, Oxford, U.K, August 1998

N(x) L   I(x) = N(x) L   SFS on a Sunny Day

I(x) = N(x) L   SFS on a Sunny Day

 (x) SFS on a Cloudy Day

 (x) = angle of visible light source I(x)   (x)   N(x)   L d L  SFS under Diffuse Lighting

Hill or Valley ?

Does Dark Means Deep? SFS under Diffuse Lighting

local intensity maximum Does Dark Means Deep?

 intensity  depth + + _ _ correlated anti-correlated Height-Intensity Correlation

Correlated Condition

Anti-Correlated Condition

1. Grey Silhouette

2. Pair of Probes

3. Test: Which is higher ?

_ percent correct N=17 Correlation Which is higher ?

Which is brighter ?

height brightness percent correct _ Correlation N=10 Which is brighter ?

I(x) =  (x) I(x) = N(x) L d L   (x)  (Langer and Zucker ‘93) (Stewart and Langer ‘96) Computational Modeling  

human LZ ‘93 SL ‘96 percent correct Human - Models

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