A visual hull is a geometric entity created by shape-from-silhouette
3D reconstruction
In computer vision and computer graphics, 3D reconstruction is the process of capturing the shape and appearance of real objects.
This process can be accomplished either by active or passive methods. If the model is allowed to change its shape i ...
technique introduced by A. Laurentini. This technique assumes the foreground object in an image can be
separated from the background. Under this assumption, the original image can be thresholded into a foreground/background binary image, which we call a silhouette 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-projected
generalized cone that contains the actual object. This cone is called a ''silhouette cone''. The upper right thumbnail shows two such cones produced from two silhouette images taken from different viewpoints. The intersection of the two cones is called a visual hull,
which is a
bounding geometry of the actual 3D object (see the bottom right thumbnail). 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.
In two dimensions
A technique used in some modern
touchscreen
A touchscreen or touch screen is the assembly of both an input ('touch panel') and output ('display') device. The touch panel is normally layered on the top of an electronic visual display of an information processing system. The display is often ...
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 the
convex hull
In geometry, the convex hull or convex envelope or convex closure of a shape is the smallest convex set that contains it. The convex hull may be defined either as the intersection of all convex sets containing a given subset of a Euclidean space ...
of the object.
See also
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3D reconstruction from multiple images
3D reconstruction from multiple images is the creation of three-dimensional models from a set of images. It is the reverse process of obtaining 2D images from 3D scenes.
The essence of an image is a projection from a 3D scene onto a 2D pla ...
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Tomographic reconstruction
Tomographic reconstruction is a type of multidimensional inverse problem where the challenge is to yield an estimate of a specific system from a finite number of projections. The mathematical basis for tomographic imaging was laid down by Johann ...
References
{{Mixed reality
Computer graphics
Geometry in computer vision
Projective geometry
Photogrammetry
3D imaging
Convex hull algorithms