Dear All, Thanks to what I found here http://bit.ly/1qJlWkP I discovered how to plot the convex hull around a set of points (please have a look at the script pasted at the end of the email). Everything is almost done,but I have a problem: my "points" are not really point-like: they are sphere whose radius is 1 and they almost touch each other. I do not know how to tune the parameter s so that the radius of the points is equal to one in the same units in which I measure the positions of the points themselves. Any help is appreciated. Cheers Lorenzo ################################################################à import numpy as np import pylab as pl import scipy as sp from scipy.spatial import ConvexHull from scipy.spatial.distance import euclidean import matplotlib.pyplot as plt import mpl_toolkits.mplot3d as a3 cluster_agglomerate=np.array([[ 0.14513811, -0.18930948, -1.44428171], [ 0.88042945, 1.67057596, -1.45742688], [-1.66682741, -0.99554261, -1.70267889], [-0.95535694, 2.3159907 , -1.93637881], [ 1.09396798, 1.7987614 , -3.44524095], [-2.63620654, 0.16588691, -3.02436539], [ 0.19027056, 2.70740725, 0.11479029], [ 2.77638842, 1.70535678, -2.10208878], [-0.09149779, -0.81908733, 2.07425244], [-0.48408772, 0.96793567, 1.26652603], [ 0.67499278, -2.5386008 , 1.39914827], [ 1.02571108, -1.60932884, -0.34500693], [ 2.78789155, -1.42050584, 0.59682802], [-0.14688239, -2.36883246, 3.35177362], [-1.71507089, 0.19184887, 2.68408562], [-1.87886026, -1.58255618, 3.97006406], [ 6.61540229, 1.98324725, 0.82767368], [ 7.46818823, 3.00950487, -0.66214223], [ 4.80777628, 1.97159273, 1.68344958], [ 6.3548727 , 2.26459561, 2.92819854], [ 4.70026626, 0.44618044, 0.3866837 ], [ 3.44366671, 1.87939977, -0.2203051 ], [ 2.92460648, 1.98510457, 2.37510769], [ 5.07053866, -0.10349542, -1.51041234], [ 7.21643437, -1.32050186, -0.70707322], [ 6.93292243, 0.58458074, -1.2458508 ], [ 7.84238244, -2.97562362, -1.63914669], [ 7.43212373, 0.10620418, 0.68315389], [ 9.59692827, -2.0843759 , -1.26623658], [ 8.34540867, -1.14927294, 1.95073173], [ 6.57425162, -2.13797392, -2.94804639], [ 6.93340304, -4.4591665 , -0.63578546]]) # see http://bit.ly/1qJlWkP # Generate random points & convex hull points = cluster_agglomerate # np.random.rand(20,3) print "points are, ", points hull = ConvexHull(points) print "I calculated the convex hull" ax = a3.Axes3D(pl.figure()) facetCol = [1, 0.0, 0.0] ax.plot_trisurf(points[:,0], points[:,1], points[:,2], triangles=hull.simplices) ax.scatter(points[:,0], points[:,1], points[:,2], s=100) plt.axis('off') plt.show()