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DIRECT SHAPE FROM ISOPHOTES V.Dragnea, E.Angelopoulou
 

Summary: DIRECT SHAPE FROM ISOPHOTES
V.Dragnea, E.Angelopoulou
Computer Science Department, Stevens Institute of Technology, Hoboken, NJ 07030, USA -
(vdragnea, elli)@ cs.stevens.edu
KEY WORDS: Isophotes, Reflectance Map
ABSTRACT:
This article describes a new method of Shape from Shading, Shape from Isophotes. Shape from Isophotes uses the image isophotes
for recovering the object surface normals. It is a propagation method. It initially directly recovers a small number of surface normals
and then uses them to estimate normals at neighboring points in either adjacent isophotes or within the same isophote. The
propagation can start either from occluding contours or singular points. Shape from Isophotes explicitly addresses brightness
quantization errors, which can affect the performance of traditional Shape from Shading techniques. Since our method is based on
the relationship between isophote curves and changes in surface normals [9,10], it is mainly applicable to smooth diffuse surfaces.
The accuracy of the proposed technique was measured using synthetic images of simple objects with Lambertian reflectance, as well
as real objects of known geometry. The normal map was recovered with accuracy of well bellow 7º average error. The method
requires some interpolation, as it is possible that we may not be able to recover the surface normals at each pixel
1. INTRODUCTION
There is a big body of work done in the field of Shape from
Shading (SFS), [1,2,3,4,5,7,8,11,12,14,15] just to mention a
few. Despite their inherent limitations (they often need input
images of scenes with strong parallel illumination rays and/or

  

Source: Angelopoulou, Elli - Department of Computer Science, Friedrich Alexander University Erlangen Nürnberg

 

Collections: Computer Technologies and Information Sciences