Two silhouette cones produced from two silhouette images taken from different viewpoints.Visual hull resulting from the intersection of two silhouette cones.
Avisual hull is a geometric entity created by shape-from-silhouette3D reconstruction technique introduced by A. Laurentini.
This technique assumes the foreground object in an image can beseparated from the background. Under this assumption, the original image can be thresholded into a foreground/backgroundbinary image, which we call asilhouette image. The foreground mask, known as a silhouette, is the 2D projection of the corresponding 3D foreground object. Along with the camera viewing parameters, the silhouette defines a back-projectedgeneralized cone that contains the actual object; this cone is called asilhouette cone. The intersection of the two silhouette cones defines a visual hull.[1] which is abounding geometry of the actual 3D object. When the reconstructed geometry is only used for rendering from a different viewpoint, the implicit reconstruction together with rendering can be done using graphics hardware.[2]
A technique used in some moderntouchscreen devices employs cameras placed in the corners situated opposite infrared LEDs. The one-dimensional projection (shadow) of objects on the surface may be used to reconstruct theconvex hull of the object.[citation needed]
Visual hull generation method has also been used within experimental tele-meeting systems[3] that aim to allow a user in a remote location to interact with virtual objects. The method uses multiple cameras to capture the real-world movements and interactions of the "sender", employing hardware-accelerated volumetric visual hull representation to create 3D volume from 2D multi-view images. Its ultimate aim is to allow 3D collaboration between the two users in the virtual realm, with the visual hull technique reducing the computational power required to allow this type of interaction and enabling the use of consumer goods such as the Wii Remote as a tool for interaction.
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