Vtk Warp

Animate a warped PyVista surface with a Player widget. The temporal function is inspired by the HoloViews Live Data guide.

import numpy as np
import panel as pn
import pyvista as pv

pn.extension('vtk', sizing_mode="stretch_width")

Surface

A flat plane carries the values of the temporal function at time=0.

alpha = 2
xvals = np.linspace(-4, 4, 101)
yvals = np.linspace(-4, 4, 101)
xs, ys = np.meshgrid(xvals, yvals)

def time_function(time):
    return np.sin(((ys/alpha)**alpha+time)*xs)

mesh_ref = pv.ImageData(
    dimensions=(xvals.size, yvals.size, 1),
    spacing=(xvals[1]-xvals[0], yvals[1]-yvals[0], 1),
    origin=(xvals.min(), yvals.min(), 0)
)
mesh_ref.point_data['values'] = time_function(0).flatten(order='F')
pl_ref = pv.Plotter()
pl_ref.add_mesh(mesh_ref, cmap='rainbow')

pn.ui.VTK(pl_ref.ren_win, min_height=600)

Animation

We warp the surface by its values and update it for each player frame. VTK meshes are mutated in place, so synchronize() pushes the new state to the browser.

mesh_warped = mesh_ref.warp_by_scalar()
pl = pv.Plotter()
pl.add_mesh(mesh_warped, cmap='rainbow')

camera = {
    'position': [13.443258285522461, 12.239550590515137, 12.731934547424316],
    'focalPoint': [0, 0, 0],
    'viewUp': [-0.41067028045654297, -0.40083757042884827, 0.8189500570297241]
}
vtkpan = pn.ui.VTK(pl.ren_win, orientation_widget=True, sizing_mode='stretch_both', camera=camera)
frame = pn.ui.Player(value=0, start=0, end=50, interval=100, loop_policy="reflect")

def update_3d_warp(value):
    # The player runs from 0 to 50 but the function is animated over 0 to 10.
    data = time_function(value / 5).flatten(order='F')
    mesh_ref.point_data['values'] = data
    mesh_warped.point_data['values'] = data
    mesh_warped.points = mesh_ref.warp_by_scalar(factor=0.5).points
    vtkpan.synchronize()

pn.bind(update_3d_warp, frame, watch=True)

main = pn.ui.Column(
    pn.ui.Markdown("This app demonstrates the use of Panel to animate a `VTK` rendering."),
    frame,
    vtkpan,
    min_height=800
)

page = pn.ui.Page(main=[main], title='VTK Warp')

page

Served App

if pn.state.served:
    page.servable()