## [Matplotlib-users] plot a triangular mesh

 [Matplotlib-users] plot a triangular mesh From: Ondrej Certik - 2009-05-22 02:32:04 Attachments: mpl1.png     mayavi.png ```Hi, I have a set of vertices in 2D as triples (x, y, val), where the x, y are 2D coordinates and "val" is the scalar value of the finite element solution, here is an example: In [54]: l.get_vertices() Out[54]: array([[ 0.00000000e+00, -1.00000000e+00, -2.22396971e-17], [ 1.00000000e+00, -1.00000000e+00, -1.64798730e-17], [ -1.00000000e+00, 0.00000000e+00, 8.09899023e-17], ..., [ 1.48437500e-01, -1.56250000e-02, 1.62359362e-01], [ 1.32812500e-01, 0.00000000e+00, 1.56012622e-01], [ 1.32812500e-01, -1.56250000e-02, 1.50562411e-01]]) and I also have a set of triangles that connect those points, here is an example: In [55]: l.get_triangles() Out[55]: array([[ 3, 5448, 29], [ 27, 5445, 28], [ 29, 28, 26], ..., [5499, 5498, 5479], [5510, 5493, 5491], [5513, 5508, 5491]], dtype=int32) The triangles define the 2D domain. What is the best way to get this plotted with mpl? Should I write a loop using the "plot" command, or is there a better alternative? So far, I am using the contour command and I feed it just with the vertices, here is the code: vert = lin.get_vertices() from numpy import min, max, linspace from matplotlib.mlab import griddata import matplotlib.pyplot as plt # make up data. #npts = int(raw_input('enter # of random points to plot:')) npts = 200 x = vert[:, 0] y = vert[:, 1] z = vert[:, 2] # define grid. xi = linspace(min(x), max(x), 100) yi = linspace(min(y), max(y), 100) # grid the data. zi = griddata(x,y,z,xi,yi) # contour the gridded data, plotting dots at the nonuniform data points. CS = plt.contour(xi,yi,zi,15,linewidths=0.5,colors='k') CS = plt.contourf(xi,yi,zi,15,cmap=plt.cm.jet) plt.colorbar() # draw colorbar plt.title('Solution (%d points)' % npts) The output of which is attached. It looks ugly, because mpl doesn't have enough information about the domain. Mayavi can use this information with this script: vert = lin.get_vertices() triangles = lin.get_triangles() from numpy import zeros from enthought.mayavi import mlab x = vert[:, 0] y = vert[:, 1] z = zeros(len(y)) t = vert[:, 2] # the off screen rendering properly works only with VTK-5.2 or above: mlab.options.offscreen = True s = mlab.triangular_mesh(x, y, z, triangles, scalars=t) mlab.view(azimuth=90, elevation=180) the output of which is attached. Mayavi is good, but it's a little overkill for this purpose, as it takes a while to start etc. I want to use it inside the Sage notebook, where matplotlib is faster and takes less memory. Also it's way easier to install (e.g. no vtk, and fiddling with os mesa). Thanks for any ideas. Ondrej ```