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Questions tagged [qhull]

Qhull is a library for C and C++ which implements Quickhull algorithm for computing the convex hull.

Qhull is a library for C and C++ which implements Quickhull algorithm for computing the convex hull.

Homepage: http://www.qhull.org/html

Qhull computes the convex hull, Delaunay triangulation, Voronoi diagram, halfspace intersection about a point, furthest-site Delaunay triangulation, and furthest-site Voronoi diagram. The source code runs in 2-d, 3-d, 4-d, and higher dimensions.

Qhull handles roundoff errors from floating point arithmetic. It computes volumes, surface areas, and approximations to the convex hull.

Qhull does not support triangulation of non-convex surfaces, mesh generation of non-convex objects, medium-sized inputs in 9-D and higher, alpha shapes, weighted Voronoi diagrams, Voronoi volumes, or constrained Delaunay triangulations,

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3d surface plot with xyz coordinates

I am hoping someone with experience can help in how one prepares the shape files from xyz data. A great example of a well-prepared dataset can be seen here for the comet Churyumov–Gerasimenko, although the preceding steps in creating the shape file…
Marc in the box
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Speedup scipy griddata for multiple interpolations between two irregular grids

I have several values that are defined on the same irregular grid (x, y, z) that I want to interpolate onto a new grid (x1, y1, z1). i.e., I have f(x, y, z), g(x, y, z), h(x, y, z) and I want to calculate f(x1, y1, z1), g(x1, y1, z1), h(x1, y1, z1).…
s_haskey
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qhull Library - C++ Interface

The qhull library ( qhull.org) has several examples to start in his website, but all the information regarding to the C++ is not very useful to me. I am trying to make a simple convex Hull of 3D points that I read from a file, I can´t use the…
Nuno Pessanha Santos
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Volume of convex hull with QHull from SciPy

I'm trying to get the volume of the convex hull of a set of points using the SciPy wrapper for QHull. According to the documentation of QHull, I should be passing the "FA" option to get the total surface area and volume. Here is what I get.. What…
Diana
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Volume of Voronoi cell (python)

I'm using Scipy 0.13.0 in Python 2.7 to calculate a set of Voronoi cells in 3d. I need to get the volume of each cell for (de)weighting output of a proprietary simulation. Is there any simple way of doing this - surely it's a common problem or a…
Chris H
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LinearNDInterpolator -- Qhull precision error: Initial simplex is flat

I am attempting to use scipy.interpolate.LinearNDInterpolator() to interpolate data points in an 8-dimensional space and am getting an error I don't understand: scipy.spatial.qhull.QhullError: QH6154 Qhull precision error: Initial simplex is flat…
The Ledge
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3D Extrapolation in python (basically, scipy.griddata extended to extrapolate)

I am using the griddata function in scipy to interpolate 3 and 4 dimensional data. It works like a champ, except that it returns a bunch of NaNs because some of the points I need are outside the range of the input data. Given that N-d data only…
Alex
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Scipy ConvexHull and QHull: rank/dimension is not maximal

I am trying to create a Convex Hull using the library Scipy and ConvexHull. As far as I know, it calls QHull. The problem appears when the points I want to add do not have 'full dimension'. Example: from scipy.spatial import ConvexHull import numpy…
Jesus Martinez Garcia
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Difference between Matlab delaunayn and Scipy Delaunay

I'm trying to replicate an N dimensional Delaunay triangulation that is performed by the Matlab delaunayn function in Python using the scipy.spatial.Delaunay function. However, while the Matlab function gives me the result I want and expect, scipy…
zephyr
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C++ CMake FLANN failing when building pcl in vs2012

Trying to build PCL on VS2012 in Windows 8.1 so I can attempt to integrate my Kinect for Windows v2 sensor with it, however I seem to be running into a bunch of CMake errors that I don't know what to do with. this is partially because I am not very…
physincubus
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voronoi and lloyd relaxation using python/scipy

How to determine, using Qhull, which voronoi cells (by index) are "proper" (made of "existing vertices") I am trying to perform a constrained relaxation using LLoyds algorithm and input generated by scipy.spatial Voronoi (which is a wrapper for…
Chris
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Constraining the Domain of Voronoi Vertices Generated by Qhull

My question in short: Is it possible to constrain the domain of the Voronoi vertices generated by Qhull? If so, how can one do so? My question with context: I am working on a data visualization in which I have points in a 2D field. The points…
duhaime
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Find the projection of a point on the convex hull with Scipy

From a set of points, I'm getting the convex hull with scipy.spatial, either with Delaunay or ConvexHull (from the qhull library). Now I would like to get the projection of a point outside this convex hull onto the hull (i.e. the point on the hull…
Jean
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Voronoi diagram using custom (great circle) distance

I want to create a Voronoi diagram on several pairs of latitudes/longitudes, but want to use the great circle distance between them, not the (inaccurate) Pythagorean distance. Can I make qhull/qvoronoi or some other Linux program do this? I…
user354134
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Why does Qhull error when computing convex hull of a few points?

I'm trying to compute the convex hull of 9 points in 10 dimensional space. Through the scipy interface, I'm calling scipy.spatial.ConvexHull(points) and getting QH6214 qhull input error: not enough points(9) to construct initial simplex (need 12) I…
Mark
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