MATLAB Function Reference |
Syntax
Description
K = convhulln(X)
returns the indices K
of the points in X
that comprise the facets of the convex hull of X
. X
is an m
-by-n
array representing m
points in N-dimensional space. If the convex hull has p
facets then K
is p
-by-n
.
K = convulln(X, options)
specifies a cell array of strings options
to be used as options in Qhull. The default options are:
If options
is []
, the default options are used. If options
is {''}
, no options are used, not even the default. For more information on Qhull and its options, see http://www.qhull.org/.
[K, v] = convhulln(...)
also returns the volume v
of the convex hull.
Visualization
Plotting the output of convhulln
depends on the value of n
:
n = 2
, use plot
as you would for convhull
.
n = 3
, you can use trisurf
to plot the output. The calling sequence is
For more control over the color of the facets, use patch
to plot the output. For an example, see Tessellation and Interpolation of Scattered Data in Higher Dimensions in the MATLAB documentation.
Example
The following example illustrates the options
input for convhulln
. The following commands
Warning: qhull precision warning: The initial hull is narrow (cosine of min. angle is 0.9999999999999998). A coplanar point may lead to a wide facet. Options 'QbB' (scale to unit box) or 'Qbb' (scale last coordinate) may remove this warning. Use 'Pp' to skip this warning.
To suppress the warning, use the option 'Pp'
.The following command passes the option 'Pp'
, along with the default 'Qt'
, to convhulln
.
Algorithm
convhulln
is based on Qhull [2]. For information about Qhull, see http://www.qhull.org/. For copyright information, see http://www.qhull.org/COPYING.txt.
See Also
convhull
, delaunayn
, dsearchn
, tsearchn
, voronoin
Reference
[1] Barber, C. B., D.P. Dobkin, and H.T. Huhdanpaa, "The Quickhull Algorithm for Convex Hulls," ACM Transactions on Mathematical Software, Vol. 22, No. 4, Dec. 1996, p. 469-483. Available in PDF format at http://www.acm.org/pubs/ citations/journals/toms/1996-22-4/p469-barber/.
[2] National Science and Technology Research Center for Computation and Visualization of Geometric Structures (The Geometry Center), University of Minnesota. 1993.
convhull | convn |
© 1994-2005 The MathWorks, Inc.