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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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Scipy: Qhull options to ensure each point is isolated in distinct Voronoi region

I am working on a problem that calls for a Voronoi tesselation of a plane. I thought that in the Voronoi tesselation, each point would be contained in a unique cell of the Voronoi map, e.g. In that illustration points are black dots, and each is…
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Error when using ConvexHull to find boundaries of objects in 3D image

I am trying to find the hull of a few objects in an image stack. They are microscope images of cells. I'm using ConvexHull from scipy to do so. The image stack is of dimensions 46 x 512 x 512. I have converted it to a binary array. I tried imhull =…
JazlynnT
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Why does scipy.spatial.Voronoi() output zero regions even if there are no duplicate input points?

Why are some Voronoi regions empty? I have a point cloud of the surface of a human that I'm trying to find the Voronoi diagram of. So I found scipy.spatial.Voronoi(), including some pretty good documentation. But sometimes vor.regions includes…
platonicity
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Plot convex hull given by quickhull algorithm in R (convhulln function)

I need to plot the convex hull given by quickhull algorithm in R. Here is an example. library(geometry) x1 <- rnorm(100, 0.8, 0.3) y1 <- rnorm(100, 0.8, 0.3) ConVexHull<-convhulln(cbind(x1,y1),"FA") ConVexHull$hull gives a m-by-dimension index…
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griddata: QH6214 qhull input error: not enough points(2) to construct initial simplex

I am trying to create an above-head view heat map of relatively sparse EEG data (27 electrodes). I convert x,y cartesian coordinates of the EEG electrodes to polar, and attempt to map them as such. Each x,y coordinate corresponds to a given value…
philosonista
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Getting Voronoi diagram info from C++ interface of the Qhull library

I'm using the Qhull library with the C++ interface. Basically what I've been trying to do is get Voronoi diagram info out of it, such as Voronoi regions, vertices, facets, etc. However, the interface seems to be incomplete. Right now I can only…
eduard626
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QuickHull worst case

QHull (and perhaps other good implementations of QuickHull) works really well and fast in many cases. However, we know theoretically that its worst case can be O(n^2). In practice I have not seen any numerical example with many dimensions (i.e., 20…
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How to Suppress Qhull Message using scipy.spacial ConvexHull

Using ConvexHull(coordinates, qhull_options="QJ") every once in a while I get a large number of the message Killing degenerate triangle in stdout. There are no errors or suspicious results. So it looks like qhull successfully removed some degenerate…
greyeagle
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qhull library is not loaded in python

I recently installed a package that only runs with python2.7. Within this package, qhull is imported by import matplotlib._qhull as _qhull which leads to getting this…
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How to use Qhull as an external project in CMake?

I have tried to use QHull and libqhullcpp as an external project in CMake, but I was not successful. So far I've used these commands which is a modified version of this: include(ExternalProject) ExternalProject_add(qhull GIT_REPOSITORY…
Sina Masnadi
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Computing the upper convex hull in 3d using Qhull

I am trying to compute the upper convex hull of a cloud of point in 3D using Qhull. I do not know if there is a simple way to do it. I've looked into several options of the modules ConvexHull and Delaunay, 'Qu' furthest site, but i do not think it…
Gregoire Fournier
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MATLAB `convnhulln` doesn't support Qhull normals option?

Suppose I have a set of vertices, e.g. V = [ 0 0 ; 1 0 ; 0 1] and I want to construct their convex hull in MATLAB. Using the convhulln command, I can extract the vertex indices for the facets of the hull e.g. convhulln(V) yields ans = 1 2 …
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Efficient determination of adjacent cells in a Voronoi diagram from scipy.spatial.Voronoi

I'm working on an algorithm that uses Voronoi diagrams. I need to know for every given cell, which cells it has as neighbors; that is, which neighbors it shares an edge with. This is similar to an existing question. However, I already have an…
Cogitator
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Issues when computing convex hull of large dataset using qhull/SciPy

I started to experiment using the scipy.spatial.ConvexHull function, that (if I understood correctly) is a wrapper for the qhull C library. I am using SciPy 0.19.1 with Python3. I first worked with a real-world dataset that features 700 points in 21…
Alberto
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Qhull Convex hull wants me to input at least 3 points

Update: I've decided to try to use a linear programming package in order to determine if the vertices of the two polytopes are linearly separable. (The vertices are really my data, not the polytopes.) I think this will work better, so I no longer…
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