"""
.. _pump_bracket_example:

Visualize Modal Analysis of a Pump Bracket
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The following example demonstrates how to use PyVista to visualize the modal
analysis of a pump bracket based on point arrays representing mode shapes for
different modes of vibration.

**Background**
Modal analysis is the study of the dynamic properties of mechanical structures
in the frequency domain. It is a common technique in structural dynamics,
particularly for automotive, aerospace, and civil engineering applications.

A mode shape is the deformation pattern that occurs at a specific natural
frequency, or mode, of a structure. When a structure is excited by an external
force, it responds at all its natural frequencies with each mode shape being
independent of the others. In this example, we will visualize the mode shapes
to get an understanding of how the pump bracket responds to different modes of
vibration.

"""

import numpy as np
import pyvista as pv
from pyvista import examples

# %%
# Load the dataset
# ~~~~~~~~~~~~~~~~
# Start by loading the dataset using :func:`download_pump_bracket()
# <pyvista.examples.downloads.download_pump_bracket>`.
#
# This example demonstrates the visualization of the pump bracket's mode shape,
# the representation of its magnitude, and an animation of its displacement. The
# dataset used in this example contains 10 mode shapes (disp_0 to disp_9).

dataset = examples.download_pump_bracket()
dataset


# %%
# Plot the Dataset
# ~~~~~~~~~~~~~~~~
# Choose a mode shape from the available arrays in the dataset. Each "disp_N"
# array represents an eigen solution or a single mode shape for a given mode of
# vibration.
#
# Plot the 4th mode of the dataset. This is the first torsional mode for the
# bracket.

cpos = pv.CameraPosition(
    position=(0.744, -0.502, -0.830),
    focal_point=(0.0520, -0.160, 0.0743),
    viewup=(-0.180, -0.958, 0.224),
)

dataset.plot(
    scalars='disp_3',
    cpos=cpos,
    show_scalar_bar=False,
    ambient=0.2,
    anti_aliasing='fxaa',
)


# %%
# Visualize Displaced Mode Shape
# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# We will now visualize the mode shapes of the pump bracket by displacing the
# original dataset using :func:`warp_by_vector <pyvista.DataSetFilters.warp_by_vector>`.

# Create a plotter
pl = pv.Plotter()

# Add the undeformed pump bracket
pl.add_mesh(dataset, color='white', opacity=0.5)

# Add the deformed pump bracket with the mode shape
warp = dataset.warp_by_vector('disp_2', factor=0.1)
pl.add_mesh(warp, show_scalar_bar=False, ambient=0.2)

pl.camera_position = cpos
pl.enable_anti_aliasing('fxaa')
pl.show()


# %%
# Animate the Mode Shape Displacement
# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# Animate the mode shape's displacement by updating the vertex positions at
# each time step. For a more realistic animation, we use a sinusoidal function
# to vary the displacement.

# feel free to change this to visualize different mode shapes
mode_shape = 'disp_6'

# copy the dataset as we will modify its coordinates
ds = dataset.copy()

pl = pv.Plotter(off_screen=True)
pl.add_mesh(ds, lighting=True, color='w')
pl.camera_position = cpos
pl.enable_anti_aliasing('fxaa')

n_frames = 10
pl.open_gif('pump_bracket_mode_shape.gif')
for phase in np.linspace(0, 2 * np.pi, n_frames, endpoint=False):
    # use the original unmodified points, modify copy inplace
    ds.points = dataset.points + ds[mode_shape] * np.cos(phase) * 0.05
    pl.write_frame()

pl.close()
