libigl_Martin/python/tutorial/306_EigenDecomposition.py

# Add the igl library to the modules search path
import sys, os
sys.path.insert(0, os.getcwd() + "/../")

import pyigl as igl

V = igl.eigen.MatrixXd()
U = igl.eigen.MatrixXd()
F = igl.eigen.MatrixXi()

c = 0
bbd = 1.0
twod = False

if not igl.read_triangle_mesh("../../tutorial/shared/beetle.off",V,F):
    print("failed to load mesh")

twod = V.col(2).minCoeff() == V.col(2).maxCoeff()
bbd = (V.colwiseMaxCoeff() - V.colwiseMinCoeff()).norm()

L = igl.eigen.SparseMatrixd()
M = igl.eigen.SparseMatrixd()

igl.cotmatrix(V,F,L)
L = -L
igl.massmatrix(V,F,igl.MASSMATRIX_TYPE_DEFAULT,M)
k = 5

D = igl.eigen.MatrixXd()
if not igl.eigs(L,M,k+1,igl.EIGS_TYPE_SM,U,D):
    print("Eigs failed.")

U = (U-U.minCoeff())/(U.maxCoeff()-U.minCoeff());

viewer = igl.viewer.Viewer()

def key_down(viewer,key,mod):
    global U, c

    if key == ord(' '):
        U = U.rightCols(k)

        # Rescale eigen vectors for visualization
        Z = bbd*0.5*U.col(c)
        C = igl.eigen.MatrixXd()
        igl.parula(U.col(c),False,C)
        c = (c+1)%U.cols()

        if twod:
            V.setcol(2,Z)

        viewer.data.set_mesh(V,F)
        viewer.data.compute_normals()
        viewer.data.set_colors(C)
        return True

viewer.callback_key_down = key_down
viewer.callback_key_down(viewer,ord(' '),0);
viewer.core.show_lines = False
viewer.launch()