In [21]:

    

%pylab inline
import pyhull
import string
from pyhull.simplex import Simplex


    

    




Populating the interactive namespace from numpy and matplotlib

In [22]:

    

class MyConvexHull(object):
    
    def __init__(self, res=None, eqs=None, points=None, facets=None):
        self.res = res
        self.eqs = eqs
        self.points = points
        self.facets = facets

    @classmethod
    def from_points(cls, points):
        res = pyhull.qconvex('n i', points)
        n_dim = int(res[0])-1
        n_eqs = int(res[1])
        eqs = array([line.split() for line in res[2:2+n_eqs]]).astype(float)
        n_facets = int(res[2+n_eqs])
        facets = array([line.split() for line in res[3+n_eqs:3+n_eqs+n_facets]]).astype(int)
        return cls(res, eqs, points, facets)
    
    @classmethod
    def from_halfspaces(cls, interior_point, halfspaces):
        opt = 'H{:s} Fp'.format(string.join(array([0,0,0]).astype(str),','))
        res = pyhull.qhull_cmd('qhalf', opt, halfspaces)
        n_dim = int(res[0])
        n_vert = int(res[1])
        points = array([line.split() for line in res[2:2+n_vert]]).astype(float)
        return cls.from_points(points)
    
    def add_buffer(self, b):
        self.eqs[:,-1] -= b
        interior_point = (self.points[0] + self.points[1])/2 # since convex 
        return MyConvexHull.from_halfspaces(interior_point, self.eqs)
    
    def __repr__(self):
        return string.join(self.res, '\n')
    
    def contains(self, p):
        return False


    

In [31]:

    

p = rand(10,2) - 0.5
p = array(bmat([[p],[0.5*p + [0,1]] ,[0.2*p + [1,2]], [0.1*p + [2,2]]])).astype(float)

ch1 = MyConvexHull.from_points(p)
ch1 = ch1.add_buffer(0.1)
plot(p[:,0], p[:,1], 'k.')
for facet in ch1.facets:
    plot(ch1.points[facet][:,0], ch1.points[facet][:,1], 'k')


    

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