
The visual hull is a geometric entity that allows understanding capabilities and limits of the techniques for comparing or reconstructing non-convex 3D shapes using silhouettes or shadows. Broadly speaking, the visual hull VH(O,VR) of an object O relative to a viewing region VR of R3 is the largest object that produces the same silhouettes (or shadows) as O observed from viewpoints (lighted from point light sources) belonging to VR. The visual hull is also the closest approximation of O that can be obtained by volume intersection from silhouettes (or shadows) obtained with viewpoints (or point light sources) belonging to VR. All the visual hulls relative to viewing regions which: 1) completely enclose O; 2) do not share any point with the convex hull of O; are equal. This is the external visual hull of O, or simply the visual hull VH(O). If the viewing region is bounded by the object O itself, we have the internal visual hull IVH(O). The external visual hull is relevant to most practical situations.
We have developed:
 A. Bottino, A. Laurentini
        Retrieval of shape from silhouettes  
      
      In Advances in Imaging and Electron Physics, Academic Press 
ISBN: 0-12-014781-5, 296 pages, 2006
  
 A. Bottino, A. Laurentini
       The visual hull of piecewise smooth objects
      Computer Vision and Image Understanding,Volume 110, Issue 1, April 2008, Pages 7-18. (DOI)
  
  A. Bottino, A. Laurentini
       What's NEXT? An Interactive Next Best View Approach  
      
      Pattern Recognition, Vol. 39 (1), Jan. 2006, Pages 126-132
(DOI)
  
  A. Bottino, A. Laurentini
        The Visual Hull of Smooth Curved Objects  
      IEEE Transactions on Pattern Analysis and Machine Intelligence, Vol. 26, No. 
    12 , Dic. 2004, pp. 1622-1632 (PDF) 
 (DOI)
  
 A. Bottino, A. Laurentini
      Introducing a New Problem: Shape-from-Silhouette when the Relative 
    Positions of the Viewpoints is Unknown  
    IEEE Transactions on Pattern Analysis and Machine Intelligence, Vol. 25, No. 
    11 , Nov. 2003, pp. 1484 -1493 (PDF)
(DOI)
 A. Laurentini 
        Topological Recognition of Polyhedral Objects from Multiple Views  
      
      Artificial Intelligence, 127 (1) (2001) pp. 31-55 (PDF) 
  
  A. Laurentini 
        Computing the Visual Hull of Solids of Revolution  
      Pattern Recognition, Vol.32, N0.3, 1999 
  
  A. Laurentini 
        How many 2D silhouettes does it take to reconstruct a 3D object?  
      
      Computer Vision and Image Understanding,Vol. 67, No.1, July 1997 
  
  A. Laurentini 
        Comments on'Efficiently Computing and Representing Aspect Graphs 
      of Polyhedral Objects'  
      IEEE Trans. Patt. Anal. Machine Intell.,Vol.18, No.1,1996 (PDF) 
  
  A. Laurentini 
        Surface Reconstruction Accuracy for Active Volume Intersection  
      
      Pattern Reco. Letters, Vol.17, 1996 
  
  A. Laurentini 
        How far 3D shapes can be understood from 2D silhouettes  
      IEEE Trans.Pattern Anal. Machine Intell.,Vol.17, No.2, February 1995 (PDF) 
  
 A. Laurentini 
        The Visual Hull Concept for Silhouette-Based Image Understanding  
      
      IEEE Trans.Pattern Anal. Machine Intell.,Vol.16, No.2, February 1994 (PDF) 
  
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