# 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 `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 `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()

# ----------------------------------------------------------------------
# Generated by sphinx-examples-as-code https://github.com/pyvista/sphinx-examples-as-code