Types of Shading

Comparison of default, flat shading vs. smooth shading.

import pyvista
from pyvista import examples

PyVista supports two types of shading: flat and smooth shading that uses VTK’s Phong shading algorithm.

This is a plot with the default flat shading.

mesh = examples.load_nut()
mesh.plot()

Here’s the same sphere with smooth shading.

mesh.plot(smooth_shading=True)

Note how smooth shading makes edges that should be sharp look odd, it’s because the points of these normals are averaged between two faces that have a sharp angle between them. You can avoid this by enabling split_sharp_edges.

Note

You can configure the splitting angle with the optional feature_angle keyword argument.

mesh.plot(smooth_shading=True, split_sharp_edges=True)

We can even plot the edges that will be split using extract_feature_edges.

# extract the feature edges exceeding 30 degrees
edges = mesh.extract_feature_edges(
    boundary_edges=False, non_manifold_edges=False, feature_angle=30, manifold_edges=False
)

# plot both the edges and the smoothed mesh
pl = pyvista.Plotter()
pl.enable_anti_aliasing()
pl.add_mesh(mesh, smooth_shading=True, split_sharp_edges=True)
pl.add_mesh(edges, color='k', line_width=5)
pl.show()

The split_sharp_edges keyword argument is compatible with physically based rendering as well.

# plot both the edges and the smoothed mesh
pl = pyvista.Plotter()
pl.enable_anti_aliasing()
pl.add_mesh(mesh, color='w', split_sharp_edges=True, pbr=True, metallic=1.0, roughness=0.5)
pl.show()