Decimation

Decimation#

Decimate a mesh

from __future__ import annotations

import numpy as np

import pyvista as pv
from pyvista import examples

mesh = examples.download_face()

# Define a camera position that shows this mesh properly
cpos = [(0.4, -0.07, -0.31), (0.05, -0.13, -0.06), (-0.1, 1, 0.08)]
dargs = dict(show_edges=True, color=True)

# Preview the mesh
mesh.plot(cpos=cpos, **dargs)
decimate

Now let’s define a target reduction and compare the pyvista.PolyDataFilters.decimate() and pyvista.PolyDataFilters.decimate_pro() filters.

target_reduction = 0.7
print(f'Reducing {target_reduction * 100.0} percent out of the original mesh')
Reducing 70.0 percent out of the original mesh
decimate
decimate

Side by side comparison:

decimate

Decimate Polyline Mesh#

Generate a fairly slow spiral polyline mesh.

Construct a reusable plotting function for future use.

def compare_decimation(spiral, decimated):
    pl = pv.Plotter()
    pl.add_mesh(spiral, line_width=5, color='r', label='Original')
    pl.add_mesh(decimated, line_width=3, color='k', label='Decimated')
    pl.view_xy()
    pl.add_legend(face='line', size=(0.25, 0.25))

Decimate using pyvista.PolyDataFilters.decimate_polyline() filter by target of 50%.

decimated = spiral.decimate_polyline(0.5)
print(f'Original # of points:  {spiral.n_points}')
print(f'Decimated # of points: {decimated.n_points}')
Original # of points:  100
Decimated # of points: 50

The decimation looks OK at this level of reduction.

compare_decimation(spiral, decimated)
decimate

Using a larger level of reduction, 80%, leads to a much coarser level of representation.

decimated = spiral.decimate_polyline(0.8)
print(f'Original # of points:  {spiral.n_points}')
print(f'Decimated # of points: {decimated.n_points}')
Original # of points:  100
Decimated # of points: 20

The structure of the inner part of the spiral is completely lost.

compare_decimation(spiral, decimated)
decimate

To avoid errors of quickly changing features, use the maximum_error parameter. It is in units of fraction of the largest length of the bounding box. Note that it limits the level of reduction achieved.

decimated = spiral.decimate_polyline(0.8, maximum_error=0.5)
print(f'Original # of points:  {spiral.n_points}')
print(f'Decimated # of points: {decimated.n_points}')
Original # of points:  100
Decimated # of points: 45

The structure of the inner part of the spiral is captured adequately.

compare_decimation(spiral, decimated)
decimate

Tags: filter

Total running time of the script: (0 minutes 1.335 seconds)

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