204_Gradient.py 1.1 KB

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  1. import igl
  2. from iglhelpers import *
  3. V = igl.eigen.MatrixXd()
  4. F = igl.eigen.MatrixXi()
  5. # Load a mesh in OFF format
  6. igl.readOFF("../tutorial/shared/cheburashka.off", V, F)
  7. # Read scalar function values from a file, U: #V by 1
  8. U = igl.eigen.MatrixXd()
  9. igl.readDMAT("../tutorial/shared/cheburashka-scalar.dmat",U)
  10. U = U.col(0)
  11. # Compute gradient operator: #F*3 by #V
  12. G = igl.eigen.SparseMatrixd()
  13. igl.grad(V,F,G)
  14. # Compute gradient of U
  15. GU = (G*U).MapMatrix(F.rows(),3)
  16. # Compute gradient magnitude
  17. GU_mag = GU.rowwiseNorm()
  18. viewer = igl.viewer.Viewer()
  19. viewer.data.set_mesh(V, F)
  20. # Compute pseudocolor for original function
  21. C = igl.eigen.MatrixXd()
  22. igl.jet(U,True,C)
  23. # Or for gradient magnitude
  24. # igl.jet(GU_mag,True,C)
  25. viewer.data.set_colors(C);
  26. # Average edge length divided by average gradient (for scaling)
  27. max_size = igl.avg_edge_length(V,F) / GU_mag.mean()
  28. # Draw a black segment in direction of gradient at face barycenters
  29. BC = igl.eigen.MatrixXd()
  30. igl.barycenter(V,F,BC)
  31. black = p2e(np.array([[0.0,0.0,0.0]]))
  32. viewer.data.add_edges(BC,BC+max_size*GU, black)
  33. # Hide wireframe
  34. viewer.core.show_lines = False
  35. viewer.launch()