""" Computing Surface Normals ~~~~~~~~~~~~~~~~~~~~~~~~~ Compute normals on a surface. """ import numpy as np # sphinx_gallery_thumbnail_number = 2 from pyvista import examples mesh = examples.download_topo_global() mesh.plot(cmap="gist_earth", show_scalar_bar=False) # %% # Now we have a surface dataset of the globe loaded - unfortunately, the # dataset shows the globe with a uniform radius which hides topographic relief. # Using :func:`pyvista.PolyData.compute_normals`, we can compute the normal # vectors on the globe at all points in the dataset, then use the values given # in the dataset to warp the surface in the normals direction to create some # exaggerated topographic relief. # Compute the normals in-place and use them to warp the globe # %% # Now use those normals to warp the surface warp = mesh.warp_by_scalar(factor=0.5e-5) # %% # And let's see it! warp.plot(cmap="gist_earth", show_scalar_bar=False) # %% # We could also use face or cell normals to extract all the faces of a mesh # facing a general direction. In the following snippet, we take a mesh, compute # the normals along its cell faces, and extract the faces that face upward. mesh = examples.download_nefertiti() # Compute normals mesh.compute_normals(...) # Get list of cell IDs that meet condition ids = np.arange(mesh.n_cells)[mesh["Normals"][...] > ...] # Extract those cells top = mesh.extract_cells(ids) cpos = [ (-834.3184529757553, -918.4677714398535, 236.5468795300025), (11.03829376004883, -13.642289291587957, -35.91218884207208), (0.19212361465657216, 0.11401076390090074, 0.9747256344254143), ] top.plot(cpos=cpos, color=True) # %% # .. raw:: html # # # #

# #